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- เผยแพร่เมื่อ 28 ส.ค. 2024
- What is a VFD? Learn more about it here:
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---------------------------- Video Transcript --------------------------------
Today we are going to talk about what is a VFD.
In the 1880s, we saw the introduction of three-phase AC power. This was a marvelous invention by the great scientist Nikola Tesla. And running on that three-phase power was Tesla's three-phase AC motor. This was a fabulous invention. It's the greatest labor saving device of mankind, and changed our lives forever. But it had one significant drawback -- it could only run at one speed. So we have come up with many devices and inventions in order to compensate for that basic deficiency, things such as belts and pulleys, sheaves, dampers, inlet guide vanes, eddy current couplings, fluid couplings and so on. All to compensate the motor that could run in one speed.
It took us 100 years to come up with a device that could reliably and cost-effectively run the motor at different speeds. Finally, at the 1980s, we saw the introduction of the variable frequency drive, or VFD.
Now I'd like to look at the schematic of a VFD. If you look at the schematic in front of you, you will see three arrow looking devices on the left. These devices in the electrical world are called dials; in the mechanical world and plumbing world, we might think of these as check valves. They basically let the current flow in one direction that is the direction of the arrows. So we have an AC to DC converter or just converter for short, this converts the 3-phase AC power to DC. The DC that comes out of this is rather choppy and not very smooth. So we put in a capacitor in order to clean that DC power up. A capacitor is like a reservoir in a plumbing circuit, and that reservoir soothes everything out and gives us a nice, clean DC.
Then going to the right, we see 6 switches. These 6 switches compose the DC to AC inverter or just inverter for short. So by switching these switches on and off, we can create any frequency that we like. And that frequency will regulate the speed the motor goes. So this entire circuit is called a variable frequency drive. If you have heard terms such as variable speed drive, adjustable frequency drive, adjustable frequency AC drive, variater; all of these are just synonyms for the variable frequency drive.
Now let's take a look at an actual variable frequency drive. This VFD was manufactured in the 1980s. You'll see that there is a lot of spare space in this drive, so we weren't packaging it in the small packages we see now. However, the basic topology of a VFD has not changed since 1980, over the last 30 years. Now if you look at a modern drive, you will have the exact same parts but in a smaller enclosure with less space, packed together, and many times, stacked on top of one another.
We come down here with 3-phase AC, and this block you see right there is the AC to DC converter, or the dial block. There are 6 dials in there to convert the AC to DC. Then we come up here to these two blue cylinders are called capacitors. These are electrolytic capacitors that smooth out that DC. Going from these capacitors over here, we have the transistors. So there are 3 transistor blocks here. In each transistor block, we have 2 transistors. And they switch on and off, and thus create a frequency that allows us to regulate the speed of motors. This has tremendous potential for energy savings and allows us to adjust the speeds of our fans, conveyers, or process control systems.
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Excellent tutorial from a PE (Professional Engineer) drives expert. These guys know their stuff. Interesting how the input AC gets converted to DC in the drive, and then inverted back to AC. Great video.
That was a very accessible and easily understood and absorbed explanation, which takes real skill for what could potentially be a complex and difficult to understand topic - thank you
when you see a old guy explaining something you know you will be schooled properly
+Detta Megga Haha very true. Craig has over 30 years of experience!!
Especially when its an old guy explaining "new" technology. i had a 65 year old Microprocessors professor. I had a blast in the class and learned a ton. OGs know how to get it done.
DPR _ so true
You got that right. Most of young people want to be heroes and start explaining math and theory behind it, before you even get the idea what the hell are they talking about and they love it, because they think they're smart and you're stupid. Maybe they should choose another profession. Old guys have confidence and years of experience, so they don't need to show off.
Roshane Reynolds. # facts.
I learned a lot from this sales video. A VFD is actually a pretty simple device.
+Jason schmidt @3:40 this is a rectifier right?
+Jason schmidt Yes, more commonly called a bridge rectifier.
love the piping comparason as a hvac installer trying to get more into tech side helps alot ty gd video
Please send me contect number. .
Fuk!@ Finally someone smart enough to explain it in perfect terms. Thank you.
Thank you Sir for your simple yet understandable explanation.
Thank you very much sir for the easy to understand explaination.From Malaysia
Very clear and simple explanation, thanks!
Thank you. Well explained VFD simply
Who else loves Nicholas Tesla?
you all men are amazing.....and your explanation is too good
Very well presented and explained.
Sir it would really helpfull if you upload the videos regarding the designing a vfd..
thank you so much
Thank you for an excellent video.
thanks a lot it was very easy to understand
this is A very good video ..Thank you for your sharing .
Are those transistors at 4:15 creating AC just by switching ON/OFF the DC?
Sir, thanks for the video. It is useful.
This was a great explanation!
CLEAR... thank you!!
really great video, thanks!
Thank you, very well explained..
Thank you .
Nyc video...Great job....Liked it ...
But I have a doubt....
VFD uses less frequency to control the speed.But when the frequency decreases, the current will increase.There is a chance that the current may go beyond the rated current .Then how VFD is an option for speed control??
i have a question to ask and i need a answers back please
A variable frequency drive (VFD)should NOT be used for:
a. Recent fault history
b. Speed control
c. Soft start
d. Lockout/tagout
e. All the above
A variable frequency drive (VFD) in the “Running” State of a 480 Volt system has:
1. 480 Volts to the VFD
2. A motor overload
3. A “logical” run enables system
4. 1 and 2
5. 1 and 3
I presume the first answer is lock out tag out. It wouldnt really be a sufficient way to isolate something. VFDs control speed and soft starts by decreasing frequency. Modern vfd's have displays that show faults. Not too sure about the 2nd question though.
greate info , thanks
Can you use a VFD to run a 3 phase motor on single phase residential power?
Yes
tks for the video sir!
Sir u have some idea about vfd altvar 61???
Respected Team
I ve 1-P 220v VFD ranging voltage 220v to 360v, using this VFD on solar system with bore well
when applied 350 v DC the motor starts to work with slow speed & when applied 400 DC volt, the speed is faster than before but with 400v, some times error comes shown "over voltage". then we reduce the voltage by manually minus the 1 solar panel from string.
Now i want to run motor on 350 volt DC and then add 50 volt more while running motor by means adding change over switch or relays or you'll recommend
Can this Possible?
Nikola Tesla was a Serbian American inventor, electrical engineer.
Belgrade Kendo Trophy Nikola Tesla the best genius ever.
My favor scientist and inventor forever.
Westinghouse and Edison they are thieves.
The three diodes below phase 'C' are used to protect from reverse current?
If you had a single phase VFD and changed the frequency to 120hz from 60hz and connected it to a transformer stick welder would this increase the frequency ?
I find it hard to Believe it took 100 years to make a motor run at different speeds
i have a question when i check my motor load at drive side its shows 35 amps but when i checked it at motor terminal box side its changing frequently from 35 to 105 . i dont know what to do can any one help
Hello Red River Electricians
The World is Quite Here
Sir, did vfd Carry or have timer inside? Or can vfd work intermittently that is work for some time and stop later it will restart again based on the time you set it.
Yes, that is part of the parameter setting. Most VFDs have that capability. We cannot provide parameter settings since every drive is different.
wow, just the info I was looking for! But one thing is still not clear. What controls the switching speed of the semiconductors?
Michael, pause at 4:11. See the group of small wires on the left of the transistors that are not connected. Those connect to the controllers on the front of the cabinet, which you can see part of on the left of the video when paused at 4:11. That module is what manages the switching speed thus how a human operator is able to control the connected motors/equipment. These can be simple start/stop buttons (for preset speeds) or more complex (programmable) for multi-speed levels or ramp up/down. The module in the video appears to be a variable type as it contains a jog dial which would be used for adjusting the values. Hope that helps!
Jeff Bingham damn. I really wish i knew more about this stuff. I'm trying to work logic into a machine I'm building with linear actuators. All i need is pole switching. I had no idea how complex it would be
Hi Sir,
I am trying to trigger the Phase Loss fault of my VFD by supplying only 2 phase into VFD and output 3phase to Motor. After running around 3 minutes, nothing has happen, motor amp still under FLA, and VFD does not trip.
my VFD size is 5HP and my motor HP is 1HP.
I just trying to know how the fault is triggered.
Kind regards
Ray
Ray, what kind of drive do you have? Do you have single phase power?
Hi Sir,
VFD is 3Phase Input (with single phasing connection), 3Ph Output.
I even checked the DC-Bus voltage
3ph input with 3 connection - around 6036 - 6059
3ph input with 2 connection (Single Phasing) - same as above
Does VFD has the protection over single phasing ?
Kind regards
Ray
Ray,
You need to set the parameter in order to trip the VFD. For Mitsubishi VFDs, the parameter is called "Input Phase Loss Protection". It is parameter # 872. Default value is 0 (will not trip), and you can change that to 1.
what difference between VFD and Frequency Converter?
Hi Koposov, a frequency converter is designed to change a specific frequency to another specific frequency. For example, if you have 60Hz power, and your heater is 50Hz, the frequency converter will allow you to use the heater with the 60Hz power.
On the other hand, a VFD is used for speed control of an electric motor. You can adjust the frequency (speed) from 0 to 60Hz. You can also program the VFD many different ways to control the speed of the motor.
so all inverter convert AC to DC current?
Generally, an inverter converts DC to AC. For example, the gizmo that lets you power things with electric plugs from your car is an inverter.
if any one can just inverter brand between DELTA , SUNFAR , FULLING much help in 7.5 kw for hsd 6 kw spindle
Why do people build rotary phase converters? This seems way easier.
There are a few reasons. The limitation of VFDs is that you cannot have any electronics after the VFD in the circuit. If you have switches or lights, they have to be prior to the VFD. So one of the more common scenario is when you are trying to convert an entire facility that supplies single phase power. You want to get a phase converter because other than the machines, you also have transformers, lights, computers, and other electronics in the building.
Another scenario is if you do not need speed control, have multiple machines, and have single phase power; it is possibly cheaper to get a phase converter instead of multiple VFDs to convert that single phase.
Hope that helps.
That's interesting. Thanks.
Tesla DID NOT invent three phase power. It was Dolivo-Dobrovolsky
Do you called VFD an Inverter??? Because as I believe, the name Inverter is other thing....