Nice work. Another fine point: your VFD undoubtedly uses the 'V proportional to F' algorithm to keep from overdriving the motor. This means that the voltage at 30 Hz will actually be about 55 Vrms. This makes the current relatively constant, rather than increasing with decreasing frequency (which it would do if you kept input voltage constant). Going above 60 Hz in frequency, the voltage should go above 110 Vrms, but there will be a limitation due to the fact that the DC bus voltage is probably only about 170 V, so forming the sine wave approximation with PWM becomes theoretically impossible. They MAY use a voltage doubler rectifier or boost switching circuit to raise the DC bus voltage, but I doubt it for a low-cost product. It will be simple enough to find out: Use an rms voltmeter to monitor the motor input voltage and/or observe the PWM waveform with a scope. (Of course, you must take precautions to probe AC mains circuits with a mains powered oscilloscope.) I am betting that they simply limit the rms output voltage to about 110 V, even when you go above 60 Hz. The motor will run and the speed will increase with frequency, but torque will be diminished, which is probably OK for something like a grinder. BTW, there may be some parameter setting in the VFD that limits the max frequency... might be a good idea to set it such that you can't exceed wheel ratings.
I used a tek scope that is connected to an isolation transformer to look at the output and it is right around +/- 170V pulsed. The pulse voltage does not change with frequency, only the duty cycle as it attempts to approximate a sine wave. A friend of mine suggested that it might have a voltage doubler on the input to handle 120/240, but it does not seem to. I did not open the unit to measure the internal rail voltages, so can't be sure. The output pulses seem pretty consistent at +/- 170V peak, so the output signal consistently approximates 120V or 170/sqrt(2) RMS.There are settings to limit the max frequency, defaulted to 400hz. I will definitely limit them.The manual says frequency changes and loading responses are supposedly PID controlled. They even give you access to the PID constants. In case you didn't get the comment after I deleted the first video, I wanted to thank you for the corrections. I rushed making this video and really have no excuse. I didn't even catch the 340V error until I was editing it. I find it difficult to remember everything I need to say and actually say it. I really hate to relay wrong information and appreciate you taking the time to set me straight. THANK YOU.
Not easy to put together these how-to videos, and you expose yourself to all kinds of critics, many of whom are self-appointed experts. I will be very surprised, though, if it turns out that your VFD does not lower the rms output voltage as frequency declines. Otherwise, the motor current is bound to climb to unsustainable levels. The peak to peak voltage remains a constant 340V, but the duty factor should steadily go down. I am a switchmode power engineer by trade, but there may still be some things that I can learn about the subject.
The cursory look I took at the output waveform, did not vary in pulse height and I did not do any measurements relating to pulse width, so you could very easily be correct. I did not dig into the unit to get a hold of the clock, so I had a really hard time triggering on the output waveform. I relied mostly on single sequence looks and was interested in mostly showing the sin wave approximation. However my camera work left a lot to be desired. I started my career as a fiber optic engineer focused on transimpedance amps and the like, but have spent the last 25 years as a systems engineer so have lost a lot my feel for the analog world. Thanks for you feedback, what you share helps more people than me.
Yes, peak to peak is always double the DC bus voltage, since all the inverter output bridge does is switch bus voltage in and out. Duty factor never gets to 100%, since you need to approximate a sine wave, but DF should get proportionately lower with frequency.
You could add a switch to take the starting cap out once it is running, then you can decrease speed without the worry of the starting cap kicking in. Didn't know you could use a multiphase VFD for a single-phase motor in and out. Good to know!
I’ve been old that grinding carbide inserts using a high speed grinder can create micro fractures in the insert. Grinding carbide inserts using a slow rpm grinder avoids the problem and makes for a terrific knife sharpener.
I have heard the same. I also have heard that you should only grind an edge with the wheel moving towards the bulk of material to prevent similar damage.
If you have or are worried about overvoltage in your motor/drive just put the resistor instead of the jumper, adjust the necessary parameters and it will deal with the over-voltage
I found that you hook up 120 VAC Line to 'R' and 120 VAC N to 'T' and ground to ground and that should suffice. I saw it wired that way in videos but it really wasn't pointed out. Thanks
I suspect your bench grinder has a centrifugal switch that only disconnects the starting capacitor. when you hook it up to the VFD you can wire out both the switch and the caps
What a revelation, truly. until I saw this video i was mistakenly under the assumption that I could not vary the speed of a single phase motor. Thank You for this video.
Those are actually 3 phase VFD, typically, if the VFD detect one phase missing, it will stop the operation. However, if you force the VFD to output the phase, than you have this single phase variable frequency drive. By the way, you may need to remove the cap on the motor.
Interesting. This one doesn't. The input is a three phase full wave bridge and converts the input to DC and the creates an output (s). It doesn't need multiple phases on the input to work and was purchased because they sold it as a 117VAC to 117VAC VFD. It was clearly designed for three phase operation, but modified to be sold for this unusual task. Thanks for the tip about the running cap.
Hello, I have a question, inside your tool has a capacitor? Does that mean that you connected it directly to the inverter without removing it or did you connect it directly with a capacitor?
Question, you mention hooking up the 120VAC to any of the 2 inputs. . Do you mean that you hook up 'L' to R, S or T and 'N' to any of the other two that are not Line? Or do you hook up 'L' to R, S or T and hook 'n' - Neutral to Ground on the unit ? Thanks.
This video was made a long time ago and I don't even have this grinder anymore, but if memory serves the input would take 110V three phase (Which is not commonly used anywhere, to my knowledge) which means that you could hook up your 110V hot and neutral leads to any two of the three inputs. This particular VFD was very unusual and this may not apply to any others. Three phase inputs on VFDs typically convert the incoming legs to DC through a three phase bridge rectifier circuit.
I'm looking for a VFD to control the speed of my telescopic Rhon antenna tower lifting motor. It's a 120 volt single phase .75 horse motor. I wonder how much torque will be lost with the reduced frequency and if torque is adjustable in the programing. I need momentary remote fwd/ reverse switching and potentially limit switch input. Are these units capable of this?
The 120V VFDs are very hard to come by. I found mine quite a few years ago and it was the only one I could find at the time. I am not an expert, but with 120V systems you could use PWM or frequency changes to control speed. Torque could be retained to a point by increasing current during the shorter pulses. This only works to a limit. You have to take into consideration brush arcing and dielectric breakdown in the motor windings.
How's the motor holding up these days? My primary hesitation in doing something like this is making sure the motor doesn't overheat, as most candidates for this have what amounts to a direct drive cooling fan. Drop the RPM and the fan drops total CFM, but the same torque is still available from the motor...so you potentially have a situation where the motor is making the same heat with a lot less airflow.
I sold the grinder to make room for a Shars tool and cutter grinder. Better control on that guy. Sorry I can't give you more feedback. The observation about the fan rpm slowing is gold.
Be careful everyone what he is explaining may not be advisable see the comments below. Dudley PLEASE make it obvious in your vid's written description that this VFD is not outputting a truly phase correct single phase, nor was it meant to. It outputs 3 phase and he is using some of the legs as a hack to get a non standard variant of single phase. Others have commented below.
Your point is well taken, but this VFD was purchased as a single phase device, supposedly designed to use single phase in and out. I haven't scope'd the output, but you have me curious. Thanks for the comment.
@@DudleyToolwright it’s not single phase out it’s using IGBT transistors to change frequency the idea is they are advertising it as single Phase motor capable but that is still dangerous as the motor as you know can still overheat on the capacitor winding where it’s thinner copper t
It should but there are some caveats. Check the comments below and there are some really good warnings about using a VFD on a motor that wasn't designed for it.
I thought it would fault the drive only hooking up to two of the 3 phases on the output. Are you still able to use the over current protection and all that? These are waaayy cheaper than 1phase to 1 phase drives.
You thoughts are probably correct. This unit is a really different VFD. It puts out 120V tree phase. I suspect they just modified and existing 3 phase model for a lower output voltage. It is from China, so I don't suspect a lot of R&D went into the design.
@@DudleyToolwright I found some cheap drives with good documentation and a responsive support team all while being pretty darn cheap. They make single phase drives and even have the more advanced drive settings and protections. I believe they are identical to 3 phase drive but with some fermware that treats one of the phases accordingly to power the starting coil. With wiring diagrams to remove the starting cap. Company is called ATO. Id definitely try them out. The only thing I didn't like about the drives is that they aren't eathernet. If you wanted to control them with a computer it would need to be cerial. And im too young to appreciate cerial communication standards. But if you wanted simply enable,disable and a analog input with a simple potentiometer for adjusting speed they have those inputs for every drive.
Thanks for the video. I have a Grizzly 1/2 HP H5373 Induction Motor on a wood lathe. I want to put a VFD on it but I am not sure the motor is rated for VFD. Can you help me how to figure that out.
I am definatley not a motor expert. One thing to look out for is a centrifugal brake. If you hear the motor sound change as it slows there might be one. If there is and you use the VFD to run the motor slowly the brake might drag with bad consequences. Also, the higher voltage spikes can degrade the winding insulation and cause shorts and motor failure. I don't know how to identify motors susceptable to issues like this. Sorry I couldn't have been of more help.
You mentioned your motor is 1/2 horse so since 1HP=745.7W you need a VFD that will handle at lease 1/2 HP or 745.7W/2=372.85W So if you bought a VDF that was capable of providing 1000W, that will work fine.
@@valveman12 line reactors are how you fix the voltage spike issue. And you can add a simple on delay timer to remove the starting capacitor from the circuit. They also sell drives that have exstra contacts just for removing starting capacitors. Those drives are a bit more pricey but worth it in some applications. They only cost more because 3phase drives are so common and they are not.
@@jim4556 Hey Jim, question for you about line reactors. I'm familiar with their use in 3-phase, but not single phase. How would you wire one up in this example using 110V single phase? Just use a single terminal rather than all three? Use all three in parallel? Being a pretty niche application, are single phase reactors even a thing?
@@Skinflaps_Meatslapper the point of line reactors is to smooth out the voltage spikes. So particularly long wire runs to the motor create alot of RF noise like an antenna. But more relivantly you end up de-rateing motor winding insolation for use on a VFD since the voltage spikes will break it down. Line reactors help get around that or motors intended to be ran on VFDs have increased winding insolation. So my fear with running a single phase motor on a VFD is that there is no way that its rated for those Voltage spikes and would fail early from it. As for hooking up a line reactor I believe you would just put the line and natural through any of the 3 windings on a 3phase line reactor.
so i have a harbor frieght lathe with a 110 volt single phase motor on it i converted it to cnc.can i use this vfd to run it?also will it switch the directing the motor spins?do you have a video showing how to wire it up?
You won't be able to reverse the direction of a single phase motor with the VFD. To do this requires flipping wireing of the starter windings, unlike a three phase motor where you can swap phases. These 110V pseudo single phase vfd's are hard to come by. I chose the VFD to allow me to control the frequency and thus duty cycle to control speed. There are some potentially serious side effects of using a VFD like this. You should read some of the comments. You could destroy the motor.
thanks for the info, I have a grinder similar to the smaller one you showed in the video, I bought a motor controller and connected it to the grinder and it sounds very loudly. I wonder if I damaged the circuit?
I hope not. There are several comments made by one of the the viewers that pointed out some potential shortfalls with using a VFD with a single phase motor. Is the motor loud or the VFD? If its the VFD, it could be a fan. If it's the motor, they do sound diferent when driven by a VFD, but if the motor has a centrifugal brake and you are going slow - you could be draging the brake.
He said in the video that you could do it by fractions of a hurt but you can see on the display he is going over to the 10th place but clearly passes by the 1 and I think 2 decimal places
It can hurt the contacts and also be a problem with the winding insulation. Motors are often spec'd as "Inverter Duty" when they are specifically designed for it.
@@DudleyToolwright Thanks for the answer, I contacted Alibaba and they have dozens of 5.5kw VFD's that are single phase. And the price is not marked up 3X as we find with the USA middle man. Here in the USA these companies buy from China as all VFD's are made there, like everything else. In the USA the same VFD is $600
@@DudleyToolwright Thanks man. Would u buy it again if u had it to do over? Seems to be plenty available for 240v 1 phase to 3 phase use, but I'm Not planning on using a 3 phase motor anytime soon.
Hello.Thanks for sharing this useful clip ,i have a question, if you do not mind ,i have a 1/3 hp 110v motor and i am looking for a seeped control for that,, what do you recommend ?,and where can i find it?thanks
You have to be really careful when using a speed control on 110v single phase motors. One of the commentors was noting some of the potential issues you might have like: centrifugal brake (could go on if moving too slow), high voltage spikes could break down the insulation on the motor windings if the moter is not well enough made, etc. I found this VFD on ebay, but be carerful to actually find one that was designed for single phase 110. They can be quite hard to find.
The start winding is usually thin copper winding for the capacitor circuit in single phase motors which is sometimes a problem when you put a VFD on a single phase that start cap winding heats up a lot
I'm wondering how long your motor is going to last as most that are using VFD opt for a 3 ph induction motor. The units I've been looking at are for 1HP, 220v 3ph motors. Paired with a VFD unit 220v 1ph/ 220v 3ph. output. Interesting to see if you have motor problem later on. Not wishing you anything bad. It's difficult to find those that really understand the correct use and application for the VFD. I find motor sales reps that will just sell you anything. Then tell you...we have a 50% restocking fee if your not happy :) Liked your video.
Thanks for the comments and yes there is a possibility of damaging the motor if I am not careful. Arcing of the brushes, heating of the windings, high voltage breakdown of the winding insulative coating, and centrifugal breaking problems are some of the most likely issues. I intend to use the vfd judiciously and watch of tell tale signs of problems. Check out the comments for this video. One of the other commenters is a switching supply designer and he has a lot of useful warnings. Thanks for the comments.
With frequency follows speed. In addition the unit doesn't go much above the 500 hz range which isd definately audible. The noise is probably the windings mving slightly with the drive frequency and perhaps arcing in the brushes as well.
Interesting video! So I have an explosion proof ventilation fan 220v that I need to slow to 3/4 speed. I bought a single phase in and output 1.5kw thats says 7 amps my motor draw is 5 amps will this work on my fan? The fan is a cheap orange China atex rated any help would be great. As I need to return them if they won't work.
The unfortunate answer is: It might. The problem is that if there is a centrifugal start cap disconnect and you run the motor too slow, it may never disconnect and then you will have a failure. Also, The fast rise times of the VFD output pulses can cause issues with some types of winding insulation. One of my viewers educated me about these potential issues. Frankly, they had not occurred to me. I know this is not a great answer. Motors vary a lot. As a matter of fact, even in the 3 phase motor space, where VFDs are really common many motors will specifically say VFD compatible.
You should definitely look in the manual for the specific VFD, but in my case I was jumpering the terminals that would support the braking resistor, if I remember correctly.
There are some basic families of VFDs: 1) 3 phase to 3 phase, 2) 1 phase to 3 phase, and 3) 1 phase to 1 phase. Since most of us don't have 3 phase power, we're not interested in category 1. Meanwhile, I don't recommend following dudley's example for most power tool applications, for reasons mentioned earlier, although it may be OK for some applications, including grinders, if the motor starting circuit is OK with it. So, I try to steer people in the direction of finding an inexpensive 3-phase motor and going with the appropriate category 2 VFD. For anything above fractional horsepower, it's best to go with 220 VAC input or higher, since the currents involved are lower. The motors are widely available, because of all the conversions of 3-phase equipment to single phase. I have picked up several 3 hp motors for $50 or so each. However, a little known fact is that many category 1 VFDs will operate just fine with 1 phase input, albeit at a reduced output rating. Not all 3-phase to 3-phase VFDs will allow this type of operation. Some will flag an input error. The fact that the front-end of all VFDs is just an AC to DC rectifier is what makes this possible. If you connect single phase input to a 3-phase rectifier, you still get the required DC voltage on the 'bus', but the peak currents in the rectifiers and capacitors are higher for a given load, which is what limits output to about 2/3 of the rating. There may or may not be software features that prevent this type of operation.
Pual, is running this vfd that much better than just using a dimmer or cheap "router speed controller"? And if so how does it differ from a true single phase vdf? If you have time to answer. thank you for you insights on the subject.
@@Steve_Just_Steve if you drive an induction motor with a Triac, the results will be heat and reduced efficiency. Triacs essentially conduct for a fraction or all of the input 50Hz. ie. only the duty cycle is different but the 50Hz frequency is unchanged. VFD use DC transistors to create a variable frequency presumably with near 100% duty cycle: normal sin-wave made of 8KHz spikes to approximate sinus rise/fall. Long story short: buy yourself a 20Amp dimer to benchtest that dropping voltage of an induction motor does not really control its speed the way frequency can. 👍🏻
@@Steve_Just_Steve (The dimmer / router controller adjusts the voltage out and the power delivered. FYI Router's have universal motors, not induction motors. The VFD adjusts the frequency of the power delivered and some other magic. Induction motors want to turn at a specific RPM at 60 cycles regardless how little voltage you place on the supply line. The dimmer like control for an induction motor is not going to work, the VFD is an ideal and purpose built solution for controlling the speed of induction motors. Hope this helps .
Interesting. Just checked with Jeff Bezos and their offering for this drive says "This VFD is ONLY applicable to three phase 110V asynchronous motor." I too along with other viewers was believing that frequency drives only worked with three phase motors. Is it just an 'undocumented feature' that is allowing this unit to drive a single phase motor or will all of them do it if just try??
I would suspect that they might, but if they had intelligent vector current control or the like, that might not work out too well. The unit I bought, a few years ago, specifically said it supported single phase 110V output.
Sadly I have not found a home for my woodworking bench so I don't have a place for the grinder as of yet. As a result, I have not had the space to use it yet. I will give you follow up as soon as I can. Sorry about that.
I bought one anyway. I was mostly wondering if that grinder was a start cap/run cap and whether or not you disconnected or modified those capacitors. Or if it was a centrifugal switch if you modified that. IE keep the start capacitor from engaging at low Hz RPM and burning itself out from creating a starting wave form constantly.
Mine did not seem to have a centrifugal brake, which was a concern. I am not sure if it has a start cap or a centrifugal switch, but I don't hear one engage/disengage. I started this project but have yet to complete it because I have lost the space to put the grinder. I am waiting to get rid of a woodworking bench that is over 8 feet long to get some more useable surface space. When I do I intend to find a semi-permanent home for the grinder and will dig into this whole thing in a more thorough fashion. One of the other viewers that is a switching supply designer gave me a bunch of useful pointers that I need to look into further, including the potential starting cap issue. I have not used the grinder since the initial review. It is possible that some changes will be needed if I want to use PWM to control the speed and I intend to get into it at some point. I really appreciate you taking the time to share your insight.
I got it off of eBay. The exact item I purchased is no longer listed, but here is another: www.ebay.com/itm/2-2KW-CNC-Spindle-Motor-Speed-Control-Variable-Frequency-Drive-VFD-Inverter/122756418894?hash=item1c94da4d4e:m:mlxQKf4HjrLTt8QSumicqfg Best of luck and be careful.
for eveyone else, try to pick a single phase OUTPUT so you don't overvolt your motor running from 2 of the 3 phases instead of a referenced Neutral. Single phase motors are not great candidates for speed tricks unlike 3 phases that easily latch on a smooth rotating field with power split into 3 wires (lower currents).
I checked the serial number for the drive and it says it is made for 3 hp motors, yours is only 1/2 hp, can it have a long term bad effect? I want to use it on my 2hp motor. Thank you
I don't think that there are any issues with an over-spec'd VFD except for the possibility of a slightly lower efficiency. I am not an expert, but I think the frequency control will work identically no matter the load, unless the capabilities are exceeded, then thermal shutdown or burnt up IGBJT/MOSFETs are going to be problems.
Your vfd is 110v input correct? Output is 3 phase and you wired only two legs on U,V Can you explain more details on how that would work on 110v motor please? Thank you
The VFD I purchased is a very unusual one and it takes in 110v single phase and outputs 110v three phase. I just chose one of the phases to drive the grinder. I think this VFD will also accept 220v and output the normal 220v three phase as well.
@@DudleyToolwright thanks for your reply. I have a same vfd controller but the Manuel didn't describe anything about 220v. Only 110v to 3 phase output 110v. Maybe this inverter only work with spindle motors "stepper motor" 3 phase. Thank you
great question! I don't think you have a neutral available on the load side. Only 3 phases rotating around 360°! If you pick two of these phases do you understand that there are 120° degrees apart..? As for the RMS load voltage it's not 120V like it'd be with a usual Neutral reference. This explains why you are seing higher RMS load voltage 😁 Careful chief... [Solution: there are a few dedicated VFD for single phase induction motors that deal specifically with 90° phase shift of start winding capacitor and centrifugal SW bypass. Search the ATO.com corp] As for now I settled for a simple "Soft Starter" to make my 3450 RPM 1/2HP pump seal & bearings last forever without the destructive 7x in-rush surge. "Soft Starters" solve my No1 problem with PUMP motor controls: long service life! (See the ATS01N109FT family)
I did not remove the start capacitor. It will appear as a lower impedance to high frequencies that 60hz, so the pseudo sine wave is not ideal, but it wasn't getting too hot.
The capacitor is in series with the second motor winding, so although the capacitor will conduct more at higher frequencies, the winding (inductor) will conduct less, I think this ends up cancelling out, so it doesn't actually matter. (LC circuit)
No tell me it's not so, BAD information on TH-cam!! You mean there are not Alien ships lurking behind Saturn?? My understanding of variable frequency drives is in its infancy. I did see a video where the drill press that had one lost so much torque, in the lower frequencies, you could literally grab the chuck and stop the rotation. Thought about one for my 3hp/3ph lathe but did not want to lose torque, so I built a 5hp rotary phase converter. After watching this, I may put one on my drill press for variable speed, if I won't lose torque.
Just be careful. Changing the pulse width on a single phase motor can exceed the duty cycle limits of the motor so make sure that the motor is not overheating and there is no arcing of the brushes. Best of luck.
It would have been nice if you had covered the single phase motor strategy outlined in the manual. That's why I started watching the video in the first place. Just more click bait, kind of.
I never purposely create click bait. My titles are as accurate as I can make them. I am sorry the information you needed was not there. I really appreciate the feedback.
The bottom line is how many AMPS does this motor draw at spec.(120 volts 60 cycles)And how many amps does it draw at 3450 R.P.M.using the V.F.D.??.Nobody talks about this MOST IMPORTANT FACT.
Interesting question, are you talking about peak current or average and are you talking about the input side or the motor side? You bring up an interesting question. It never occurred to me to check because I was well within the specs of my outlet and the VFD, but if this pair was closer, answering your question would be essential. Thanks for an interesting question.
Dudley Toolwright I'm talking about when the motor is plugged into the wall at 120 volts and the motor is spinning at 3450 with no load on it?,how many amp draw is going into it,then at full load,how many amps are going into it?. Then test it again with the motor hooked up to the VFD at 3450 R.P.M.no load,then test at full load with the VFD on the motor,its that simple.⚡
Interesting. My initial guess was that when operating slower than factory the PWM (pulse width modulation) signal would generate a lower average current, but when operating faster than factory the average would be higher. Both of these estimates were the motor running in an unloaded state. The PWM of the VFD would probably increase in duty cycle to deal with higher loads for a given RPM. Changes in frequency, would I think, also cause the average current to increase. Just guessing. I will have to get a scope with current sensing to test the guesses. On another note 60hz is RF and it radiates quite well, like a radio station carrier. Such radiation is responsible for some of the hum audio mixers have to deal with. Thanks for the thought provoking questions. I have really enjoyed them.
I use woodworking wax on my table saw table and it works pretty well, but I never have direct exposure to water. For that, it doesn't work. My wife left a damp towel on the surface once and there was rust everywhere the towel was touching. I appreciate the tip.
![ILLSLICK - KILLSHOT REMIX [FULL VERSION]](http://i.ytimg.com/vi/RIK8RrqIAzE/mqdefault.jpg)
Nice work. Another fine point: your VFD undoubtedly uses the 'V proportional to F' algorithm to keep from overdriving the motor. This means that the voltage at 30 Hz will actually be about 55 Vrms. This makes the current relatively constant, rather than increasing with decreasing frequency (which it would do if you kept input voltage constant). Going above 60 Hz in frequency, the voltage should go above 110 Vrms, but there will be a limitation due to the fact that the DC bus voltage is probably only about 170 V, so forming the sine wave approximation with PWM becomes theoretically impossible. They MAY use a voltage doubler rectifier or boost switching circuit to raise the DC bus voltage, but I doubt it for a low-cost product. It will be simple enough to find out: Use an rms voltmeter to monitor the motor input voltage and/or observe the PWM waveform with a scope. (Of course, you must take precautions to probe AC mains circuits with a mains powered oscilloscope.) I am betting that they simply limit the rms output voltage to about 110 V, even when you go above 60 Hz. The motor will run and the speed will increase with frequency, but torque will be diminished, which is probably OK for something like a grinder. BTW, there may be some parameter setting in the VFD that limits the max frequency... might be a good idea to set it such that you can't exceed wheel ratings.
I used a tek scope that is connected to an isolation transformer to look at the output and it is right around +/- 170V pulsed. The pulse voltage does not change with frequency, only the duty cycle as it attempts to approximate a sine wave. A friend of mine suggested that it might have a voltage doubler on the input to handle 120/240, but it does not seem to. I did not open the unit to measure the internal rail voltages, so can't be sure. The output pulses seem pretty consistent at +/- 170V peak, so the output signal consistently approximates 120V or 170/sqrt(2) RMS.There are settings to limit the max frequency, defaulted to 400hz. I will definitely limit them.The manual says frequency changes and loading responses are supposedly PID controlled. They even give you access to the PID constants. In case you didn't get the comment after I deleted the first video, I wanted to thank you for the corrections. I rushed making this video and really have no excuse. I didn't even catch the 340V error until I was editing it. I find it difficult to remember everything I need to say and actually say it. I really hate to relay wrong information and appreciate you taking the time to set me straight. THANK YOU.
Not easy to put together these how-to videos, and you expose yourself to all kinds of critics, many of whom are self-appointed experts. I will be very surprised, though, if it turns out that your VFD does not lower the rms output voltage as frequency declines. Otherwise, the motor current is bound to climb to unsustainable levels. The peak to peak voltage remains a constant 340V, but the duty factor should steadily go down. I am a switchmode power engineer by trade, but there may still be some things that I can learn about the subject.
The cursory look I took at the output waveform, did not vary in pulse height and I did not do any measurements relating to pulse width, so you could very easily be correct. I did not dig into the unit to get a hold of the clock, so I had a really hard time triggering on the output waveform. I relied mostly on single sequence looks and was interested in mostly showing the sin wave approximation. However my camera work left a lot to be desired. I started my career as a fiber optic engineer focused on transimpedance amps and the like, but have spent the last 25 years as a systems engineer so have lost a lot my feel for the analog world. Thanks for you feedback, what you share helps more people than me.
Yes, peak to peak is always double the DC bus voltage, since all the inverter output bridge does is switch bus voltage in and out. Duty factor never gets to 100%, since you need to approximate a sine wave, but DF should get proportionately lower with frequency.
You could add a switch to take the starting cap out once it is running, then you can decrease speed without the worry of the starting cap kicking in. Didn't know you could use a multiphase VFD for a single-phase motor in and out. Good to know!
Thanks for the ideas. There are some risks and limitations as pointed out by one of the other commenters.
I’ve been old that grinding carbide inserts using a high speed grinder can create micro fractures in the insert. Grinding carbide inserts using a slow rpm grinder avoids the problem and makes for a terrific knife sharpener.
I have heard the same. I also have heard that you should only grind an edge with the wheel moving towards the bulk of material to prevent similar damage.
If you have or are worried about overvoltage in your motor/drive just put the resistor instead of the jumper, adjust the necessary parameters and it will deal with the over-voltage
Interesting approach, thanks for the idea.
I found that you hook up 120 VAC Line to 'R' and 120 VAC N to 'T' and ground to ground and that should suffice. I saw it wired that way in videos but it really wasn't pointed out. Thanks
I am glad you found a way forward. Sorry for the lack of detail.
I suspect your bench grinder has a centrifugal switch that only disconnects the starting capacitor. when you hook it up to the VFD you can wire out both the switch and the caps
I appreciate the advise, thanks.
What a revelation, truly. until I saw this video i was mistakenly under the assumption that I could not vary the speed of a single phase motor. Thank You for this video.
I'm glad it helped. Don't forget to consider the potential risks mentioned. Best of luck.
Those are actually 3 phase VFD, typically, if the VFD detect one phase missing, it will stop the operation. However, if you force the VFD to output the phase, than you have this single phase variable frequency drive. By the way, you may need to remove the cap on the motor.
Interesting. This one doesn't. The input is a three phase full wave bridge and converts the input to DC and the creates an output (s). It doesn't need multiple phases on the input to work and was purchased because they sold it as a 117VAC to 117VAC VFD. It was clearly designed for three phase operation, but modified to be sold for this unusual task. Thanks for the tip about the running cap.
Hello, I have a question, inside your tool has a capacitor? Does that mean that you connected it directly to the inverter without removing it or did you connect it directly with a capacitor?
There was a start capacitor and I did not remove it first.
Question, you mention hooking up the 120VAC to any of the 2 inputs. . Do you mean that you hook up 'L' to R, S or T and 'N' to any of the other two that are not Line? Or do you hook up 'L' to R, S or T and hook 'n' - Neutral to Ground on the unit ? Thanks.
This video was made a long time ago and I don't even have this grinder anymore, but if memory serves the input would take 110V three phase (Which is not commonly used anywhere, to my knowledge) which means that you could hook up your 110V hot and neutral leads to any two of the three inputs. This particular VFD was very unusual and this may not apply to any others. Three phase inputs on VFDs typically convert the incoming legs to DC through a three phase bridge rectifier circuit.
At least your honest about the mistakes. Great video. Cheers.
I think they would be hard to hide and besides the whole point of my channel is to show my experiences learning the trade. I am absolutely a novice.
I'm looking for a VFD to control the speed of my telescopic Rhon antenna tower lifting motor. It's a 120 volt single phase .75 horse motor. I wonder how much torque will be lost with the reduced frequency and if torque is adjustable in the programing. I need momentary remote fwd/ reverse switching and potentially limit switch input. Are these units capable of this?
The 120V VFDs are very hard to come by. I found mine quite a few years ago and it was the only one I could find at the time. I am not an expert, but with 120V systems you could use PWM or frequency changes to control speed. Torque could be retained to a point by increasing current during the shorter pulses. This only works to a limit. You have to take into consideration brush arcing and dielectric breakdown in the motor windings.
Great video easy to follow and I loved it.
Mike Hansen
Thanks. I appreciate the feedback.
How's the motor holding up these days? My primary hesitation in doing something like this is making sure the motor doesn't overheat, as most candidates for this have what amounts to a direct drive cooling fan. Drop the RPM and the fan drops total CFM, but the same torque is still available from the motor...so you potentially have a situation where the motor is making the same heat with a lot less airflow.
I sold the grinder to make room for a Shars tool and cutter grinder. Better control on that guy. Sorry I can't give you more feedback. The observation about the fan rpm slowing is gold.
@@DudleyToolwright Nice, that's definitely a step up! No worries about the feedback, I was more curious than anything.
So let me get this straight, you did not remove the caps. from the grinder motor? I am confused!
No, I did not.
Be careful everyone what he is explaining may not be advisable see the comments below. Dudley PLEASE make it obvious in your vid's written description that this VFD is not outputting a truly phase correct single phase, nor was it meant to. It outputs 3 phase and he is using some of the legs as a hack to get a non standard variant of single phase. Others have commented below.
Your point is well taken, but this VFD was purchased as a single phase device, supposedly designed to use single phase in and out. I haven't scope'd the output, but you have me curious. Thanks for the comment.
@@DudleyToolwright it’s not single phase out it’s using IGBT transistors to change frequency the idea is they are advertising it as single
Phase motor capable but that is still dangerous as the motor as you know can still overheat on the capacitor winding where it’s thinner copper t
Would this method - and particular VFD - work to halve the speed of my Makita 2412N abrasive cut-off saw down to cold cut blade speed?
It should but there are some caveats. Check the comments below and there are some really good warnings about using a VFD on a motor that wasn't designed for it.
I thought it would fault the drive only hooking up to two of the 3 phases on the output. Are you still able to use the over current protection and all that? These are waaayy cheaper than 1phase to 1 phase drives.
You thoughts are probably correct. This unit is a really different VFD. It puts out 120V tree phase. I suspect they just modified and existing 3 phase model for a lower output voltage. It is from China, so I don't suspect a lot of R&D went into the design.
@@DudleyToolwright I found some cheap drives with good documentation and a responsive support team all while being pretty darn cheap. They make single phase drives and even have the more advanced drive settings and protections. I believe they are identical to 3 phase drive but with some fermware that treats one of the phases accordingly to power the starting coil. With wiring diagrams to remove the starting cap. Company is called ATO. Id definitely try them out. The only thing I didn't like about the drives is that they aren't eathernet. If you wanted to control them with a computer it would need to be cerial. And im too young to appreciate cerial communication standards. But if you wanted simply enable,disable and a analog input with a simple potentiometer for adjusting speed they have those inputs for every drive.
Curious what your day job is? Electrician?
Electrical Engineer although my specialty is in RF not power electronics.
Thanks for the video. I have a Grizzly 1/2 HP H5373 Induction Motor on a wood lathe. I want to put a VFD on it but I am not sure the motor is rated for VFD. Can you help me how to figure that out.
I am definatley not a motor expert. One thing to look out for is a centrifugal brake. If you hear the motor sound change as it slows there might be one. If there is and you use the VFD to run the motor slowly the brake might drag with bad consequences. Also, the higher voltage spikes can degrade the winding insulation and cause shorts and motor failure. I don't know how to identify motors susceptable to issues like this. Sorry I couldn't have been of more help.
You mentioned your motor is 1/2 horse so since 1HP=745.7W you need a VFD that will handle at lease 1/2 HP or 745.7W/2=372.85W So if you bought a VDF that was capable of providing 1000W, that will work fine.
@@valveman12 line reactors are how you fix the voltage spike issue. And you can add a simple on delay timer to remove the starting capacitor from the circuit. They also sell drives that have exstra contacts just for removing starting capacitors. Those drives are a bit more pricey but worth it in some applications. They only cost more because 3phase drives are so common and they are not.
@@jim4556 Hey Jim, question for you about line reactors. I'm familiar with their use in 3-phase, but not single phase. How would you wire one up in this example using 110V single phase? Just use a single terminal rather than all three? Use all three in parallel? Being a pretty niche application, are single phase reactors even a thing?
@@Skinflaps_Meatslapper the point of line reactors is to smooth out the voltage spikes. So particularly long wire runs to the motor create alot of RF noise like an antenna. But more relivantly you end up de-rateing motor winding insolation for use on a VFD since the voltage spikes will break it down. Line reactors help get around that or motors intended to be ran on VFDs have increased winding insolation. So my fear with running a single phase motor on a VFD is that there is no way that its rated for those Voltage spikes and would fail early from it. As for hooking up a line reactor I believe you would just put the line and natural through any of the 3 windings on a 3phase line reactor.
so i have a harbor frieght lathe with a 110 volt single phase motor on it i converted it to cnc.can i use this vfd to run it?also will it switch the directing the motor spins?do you have a video showing how to wire it up?
You won't be able to reverse the direction of a single phase motor with the VFD. To do this requires flipping wireing of the starter windings, unlike a three phase motor where you can swap phases. These 110V pseudo single phase vfd's are hard to come by. I chose the VFD to allow me to control the frequency and thus duty cycle to control speed. There are some potentially serious side effects of using a VFD like this. You should read some of the comments. You could destroy the motor.
thanks for the info, I have a grinder similar to the smaller one you showed in the video, I bought a motor controller and connected it to the grinder and it sounds very loudly. I wonder if I damaged the circuit?
I hope not. There are several comments made by one of the the viewers that pointed out some potential shortfalls with using a VFD with a single phase motor. Is the motor loud or the VFD? If its the VFD, it could be a fan. If it's the motor, they do sound diferent when driven by a VFD, but if the motor has a centrifugal brake and you are going slow - you could be draging the brake.
@@DudleyToolwright I think it's the motor, I'll try again. Thank you.
Maybe I missed it in the video but where were you able to find this vfd?
This one was found on eBay, but it has been many years.
@@DudleyToolwright ahh…thanks. I’m not very up on VFDs. Need to do my homework. 👍
Dudley, does the VFD increment frequency only by 10 Hz?
I believe that it can increment by single hertz. You select the digit to modify. It has been quite a while since I have used it though.
He said in the video that you could do it by fractions of a hurt but you can see on the display he is going over to the 10th place but clearly passes by the 1 and I think 2 decimal places
Does running the motor at different frequencies put stress on the motor? Would it shorten the life expectancy?
It can hurt the contacts and also be a problem with the winding insulation. Motors are often spec'd as "Inverter Duty" when they are specifically designed for it.
@@DudleyToolwright I don't think ac induction motors have contacts. That's one of their big advantages.
Dang wish i knew you personally lol trying to get a 220single phase vfd to work with my single phase paint booth fan motor
If I can help, I am willing, but I am not an expert.
So it is a 3ph output like all of them and runs any 2 wires for single pahse or what is called 2 ph. Right?
That seems to be the case for this particular model, which is odd: 3 phase 110.
@@DudleyToolwright I am wondering which inverters have phase loss faults or what programming circuit that stops single phase powering possible.
I don't know the answer to that. Finding a single phase 110 VFD is challenging to begin with.
@@DudleyToolwright Thanks for the answer, I contacted Alibaba and they have dozens of 5.5kw VFD's that are single phase. And the price is not marked up 3X as we find with the USA middle man. Here in the USA these companies buy from China as all VFD's are made there, like everything else. In the USA the same VFD is $600
@@BroMikey55 At 5.5kw theywould be 220V VFDs, just for your information.
Thanks for sharing. Where did u buy from? - take care from Tn
I got the VFD from eBay many years ago. Single phase 110v VFD's are pretty rare.
@@DudleyToolwright Thanks man. Would u buy it again if u had it to do over? Seems to be plenty available for 240v 1 phase to 3 phase use, but I'm Not planning on using a 3 phase motor anytime soon.
I purchased the grinder from Travers, but ended up getting a Shars: Tool and Cutter Grinder. It makes up for my utter lack of hand eye coordination.
Hello.Thanks for sharing this useful clip ,i have a question, if you do not mind ,i have a 1/3 hp 110v motor and i am looking for a seeped control for that,, what do you recommend ?,and where can i find it?thanks
You have to be really careful when using a speed control on 110v single phase motors. One of the commentors was noting some of the potential issues you might have like: centrifugal brake (could go on if moving too slow), high voltage spikes could break down the insulation on the motor windings if the moter is not well enough made, etc. I found this VFD on ebay, but be carerful to actually find one that was designed for single phase 110. They can be quite hard to find.
@@DudleyToolwright thanks
The start winding is usually thin copper winding for the capacitor circuit in single phase motors which is sometimes a problem when you put a VFD on a single phase that start cap winding heats up a lot
It depends on the type of motor
Very true.
220v single phase motor what can I use??
They have single phase VFDs, but you should make sure your motor is inverter approved. Otherwise, yuo could end up damaging it.
I'm wondering how long your motor is going to last as most that are using VFD opt for a 3 ph induction motor. The units I've been looking at are for 1HP, 220v 3ph motors. Paired with a VFD unit 220v 1ph/ 220v 3ph. output. Interesting to see if you have motor problem later on. Not wishing you anything bad. It's difficult to find those that really understand the correct use and application for the VFD. I find motor sales reps that will just sell you anything. Then tell you...we have a 50% restocking fee if your not happy :) Liked your video.
Thanks for the comments and yes there is a possibility of damaging the motor if I am not careful. Arcing of the brushes, heating of the windings, high voltage breakdown of the winding insulative coating, and centrifugal breaking problems are some of the most likely issues. I intend to use the vfd judiciously and watch of tell tale signs of problems. Check out the comments for this video. One of the other commenters is a switching supply designer and he has a lot of useful warnings. Thanks for the comments.
Can the frequency output be raised to reduce the noise?
With frequency follows speed. In addition the unit doesn't go much above the 500 hz range which isd definately audible. The noise is probably the windings mving slightly with the drive frequency and perhaps arcing in the brushes as well.
Interesting video! So I have an explosion proof ventilation fan 220v that I need to slow to 3/4 speed. I bought a single phase in and output 1.5kw thats says 7 amps my motor draw is 5 amps will this work on my fan? The fan is a cheap orange China atex rated any help would be great. As I need to return them if they won't work.
The unfortunate answer is: It might. The problem is that if there is a centrifugal start cap disconnect and you run the motor too slow, it may never disconnect and then you will have a failure. Also, The fast rise times of the VFD output pulses can cause issues with some types of winding insulation. One of my viewers educated me about these potential issues. Frankly, they had not occurred to me. I know this is not a great answer. Motors vary a lot. As a matter of fact, even in the 3 phase motor space, where VFDs are really common many motors will specifically say VFD compatible.
What terminals do you put the jumper on?
You should definitely look in the manual for the specific VFD, but in my case I was jumpering the terminals that would support the braking resistor, if I remember correctly.
I've been looking for a 110 to 110 VFD. Where id you purchase it?
There are some basic families of VFDs: 1) 3 phase to 3 phase, 2) 1 phase to 3 phase, and 3) 1 phase to 1 phase. Since most of us don't have 3 phase power, we're not interested in category 1. Meanwhile, I don't recommend following dudley's example for most power tool applications, for reasons mentioned earlier, although it may be OK for some applications, including grinders, if the motor starting circuit is OK with it. So, I try to steer people in the direction of finding an inexpensive 3-phase motor and going with the appropriate category 2 VFD. For anything above fractional horsepower, it's best to go with 220 VAC input or higher, since the currents involved are lower. The motors are widely available, because of all the conversions of 3-phase equipment to single phase. I have picked up several 3 hp motors for $50 or so each.
However, a little known fact is that many category 1 VFDs will operate just fine with 1 phase input, albeit at a reduced output rating. Not all 3-phase to 3-phase VFDs will allow this type of operation. Some will flag an input error. The fact that the front-end of all VFDs is just an AC to DC rectifier is what makes this possible. If you connect single phase input to a 3-phase rectifier, you still get the required DC voltage on the 'bus', but the peak currents in the rectifiers and capacitors are higher for a given load, which is what limits output to about 2/3 of the rating. There may or may not be software features that prevent this type of operation.
I don't see any button to assign a gold star for this post, so you may have to settle for a thumbs up :)
Pual, is running this vfd that much better than just using a dimmer or cheap "router speed controller"? And if so how does it differ from a true single phase vdf? If you have time to answer. thank you for you insights on the subject.
@@Steve_Just_Steve if you drive an induction motor with a Triac, the results will be heat and reduced efficiency.
Triacs essentially conduct for a fraction or all of the input 50Hz. ie. only the duty cycle is different but the 50Hz frequency is unchanged.
VFD use DC transistors to create a variable frequency presumably with near 100% duty cycle: normal sin-wave made of 8KHz spikes to approximate sinus rise/fall.
Long story short: buy yourself a 20Amp dimer to benchtest that dropping voltage of an induction motor does not really control its speed the way frequency can.
👍🏻
@@Steve_Just_Steve (The dimmer / router controller adjusts the voltage out and the power delivered. FYI Router's have universal motors, not induction motors. The VFD adjusts the frequency of the power delivered and some other magic. Induction motors want to turn at a specific RPM at 60 cycles regardless how little voltage you place on the supply line. The dimmer like control for an induction motor is not going to work, the VFD is an ideal and purpose built solution for controlling the speed of induction motors. Hope this helps .
Great video.
Glad you enjoyed it
Interesting. Just checked with Jeff Bezos and their offering for this drive says "This VFD is ONLY applicable to three phase 110V asynchronous motor." I too along with other viewers was believing that frequency drives only worked with three phase motors. Is it just an 'undocumented feature' that is allowing this unit to drive a single phase motor or will all of them do it if just try??
I would suspect that they might, but if they had intelligent vector current control or the like, that might not work out too well. The unit I bought, a few years ago, specifically said it supported single phase 110V output.
Dudley, any updates on this VFD and how it's working a year later? Any issue with burning caps, windings, etc?
Sadly I have not found a home for my woodworking bench so I don't have a place for the grinder as of yet. As a result, I have not had the space to use it yet. I will give you follow up as soon as I can. Sorry about that.
I bought one anyway. I was mostly wondering if that grinder was a start cap/run cap and whether or not you disconnected or modified those capacitors. Or if it was a centrifugal switch if you modified that. IE keep the start capacitor from engaging at low Hz RPM and burning itself out from creating a starting wave form constantly.
Mine did not seem to have a centrifugal brake, which was a concern. I am not sure if it has a start cap or a centrifugal switch, but I don't hear one engage/disengage. I started this project but have yet to complete it because I have lost the space to put the grinder. I am waiting to get rid of a woodworking bench that is over 8 feet long to get some more useable surface space. When I do I intend to find a semi-permanent home for the grinder and will dig into this whole thing in a more thorough fashion. One of the other viewers that is a switching supply designer gave me a bunch of useful pointers that I need to look into further, including the potential starting cap issue. I have not used the grinder since the initial review. It is possible that some changes will be needed if I want to use PWM to control the speed and I intend to get into it at some point. I really appreciate you taking the time to share your insight.
Where do you buys these?
The grinder is from Travers and the VFD was from eBay.
Please post where you got the VFD from. I'm having trouble finding one, and its a great video but we need to know where you got it from.
I got it off of eBay. The exact item I purchased is no longer listed, but here is another: www.ebay.com/itm/2-2KW-CNC-Spindle-Motor-Speed-Control-Variable-Frequency-Drive-VFD-Inverter/122756418894?hash=item1c94da4d4e:m:mlxQKf4HjrLTt8QSumicqfg
Best of luck and be careful.
for eveyone else, try to pick a single phase OUTPUT so you don't overvolt your motor running from 2 of the 3 phases instead of a referenced Neutral.
Single phase motors are not great candidates for speed tricks unlike 3 phases that easily latch on a smooth rotating field with power split into 3 wires (lower currents).
I checked the serial number for the drive and it says it is made for 3 hp motors, yours is only 1/2 hp, can it have a long term bad effect? I want to use it on my 2hp motor. Thank you
I don't think that there are any issues with an over-spec'd VFD except for the possibility of a slightly lower efficiency. I am not an expert, but I think the frequency control will work identically no matter the load, unless the capabilities are exceeded, then thermal shutdown or burnt up IGBJT/MOSFETs are going to be problems.
Your vfd is 110v input correct? Output is 3 phase and you wired only two legs on U,V
Can you explain more details on how that would work on 110v motor please?
Thank you
The VFD I purchased is a very unusual one and it takes in 110v single phase and outputs 110v three phase. I just chose one of the phases to drive the grinder. I think this VFD will also accept 220v and output the normal 220v three phase as well.
@@DudleyToolwright thanks for your reply.
I have a same vfd controller but the Manuel didn't describe anything about 220v. Only 110v to 3 phase output 110v. Maybe this inverter only work with spindle motors "stepper motor" 3 phase.
Thank you
It has been quite a while since I shot this video. I am not sure about the 220V, but I did measure the 110V three phase on the output with a scope.
@@DudleyToolwright thanks for your clarification.
great question! I don't think you have a neutral available on the load side. Only 3 phases rotating around 360°!
If you pick two of these phases do you understand that there are 120° degrees apart..? As for the RMS load voltage it's not 120V like it'd be with a usual Neutral reference.
This explains why you are seing higher RMS load voltage 😁 Careful chief...
[Solution: there are a few dedicated VFD for single phase induction motors that deal specifically with 90° phase shift of start winding capacitor and centrifugal SW bypass. Search the ATO.com corp]
As for now I settled for a simple "Soft Starter" to make my 3450 RPM 1/2HP pump seal & bearings last forever without the destructive 7x in-rush surge. "Soft Starters" solve my No1 problem with PUMP motor controls: long service life! (See the ATS01N109FT family)
! phase motor always has a capasitor that can't handle high freq, did your removed it?
I did not remove the start capacitor. It will appear as a lower impedance to high frequencies that 60hz, so the pseudo sine wave is not ideal, but it wasn't getting too hot.
The capacitor is in series with the second motor winding, so although the capacitor will conduct more at higher frequencies, the winding (inductor) will conduct less, I think this ends up cancelling out, so it doesn't actually matter. (LC circuit)
Everyone take a shot when you hear caveat.
Fair. The word just fell out of my brain.
No tell me it's not so, BAD information on TH-cam!! You mean there are not Alien ships lurking behind Saturn??
My understanding of variable frequency drives is in its infancy. I did see a video where the drill press that had one lost so much torque, in the lower frequencies, you could literally grab the chuck and stop the rotation. Thought about one for my 3hp/3ph lathe but did not want to lose torque, so I built a 5hp rotary phase converter. After watching this, I may put one on my drill press for variable speed, if I won't lose torque.
Just be careful. Changing the pulse width on a single phase motor can exceed the duty cycle limits of the motor so make sure that the motor is not overheating and there is no arcing of the brushes. Best of luck.
It would have been nice if you had covered the single phase motor strategy outlined in the manual. That's why I started watching the video in the first place. Just more click bait, kind of.
I never purposely create click bait. My titles are as accurate as I can make them. I am sorry the information you needed was not there. I really appreciate the feedback.
The bottom line is how many AMPS does this motor draw at spec.(120 volts 60 cycles)And how many amps does it draw at 3450 R.P.M.using the V.F.D.??.Nobody talks about this MOST IMPORTANT FACT.
Interesting question, are you talking about peak current or average and are you talking about the input side or the motor side? You bring up an interesting question. It never occurred to me to check because I was well within the specs of my outlet and the VFD, but if this pair was closer, answering your question would be essential. Thanks for an interesting question.
Dudley Toolwright I'm talking about when the motor is plugged into the wall at 120 volts and the motor is spinning at 3450 with no load on it?,how many amp draw is going into it,then at full load,how many amps are going into it?.
Then test it again with the motor hooked up to the VFD at 3450 R.P.M.no load,then test at full load with the VFD on the motor,its that simple.⚡
Thanks for the clarification. I'll have to measure those values. Are you expecting the VFD in-circuit values to be much higher? Peak or Average?
Dudley Toolwright I'm expecting the average and peak to be much lower because your driving the motor with RF and NOT 60 cycle"electricity".
Interesting. My initial guess was that when operating slower than factory the PWM (pulse width modulation) signal would generate a lower average current, but when operating faster than factory the average would be higher. Both of these estimates were the motor running in an unloaded state. The PWM of the VFD would probably increase in duty cycle to deal with higher loads for a given RPM. Changes in frequency, would I think, also cause the average current to increase. Just guessing. I will have to get a scope with current sensing to test the guesses. On another note 60hz is RF and it radiates quite well, like a radio station carrier. Such radiation is responsible for some of the hum audio mixers have to deal with. Thanks for the thought provoking questions. I have really enjoyed them.
Use coolant, not water..
Yea. I misspoke. I have coolant for the grinder, but called it water. Thanks for catching that goof.
CAST IRON RUSTING... Use plain old any car wax... Wax the cast iron every so often. Also great because less friction.
I use woodworking wax on my table saw table and it works pretty well, but I never have direct exposure to water. For that, it doesn't work. My wife left a damp towel on the surface once and there was rust everywhere the towel was touching. I appreciate the tip.