Nice detailed explanation - much better than the usual "connect it to a Chinese triac" videos, thank you. By the way, i love your accent and really appreciate you making your videos in English!
It should be interesting to control separately the stator and the rotor windings. Universal motor can also be used as generator, such as in a wind generator, in such scenario, the separate control of the two windings should be very important to control the generated voltagy and the speed of the blades.
Indeed it would be interesting to seprately control the field and the rotor's current. But Universal motors have the stator's winding designed to widthstand high current, unlike classic DC motors with separated field excitation that use much less current to generate pretty strong magnetic fields. This could negatively affect the efficiency of the motor.
Just subscribed. I'm finding your video's much easier to follow than many on You Tube. I've wanted to understand electronics for a long time, as a motorcycle tech I had basic understanding of electrical systems (charging and ignition, diodes, transistors and capacitors) but I'm retired now so can spend more time on learning about electronics. Your not assuming things or 'talking down' to people who don't know this stuff (me 😄) Are you an electronics lecturer/ tutor/ teacher/engineer? Your whiteboard drawing are real good
Molto bravo complimenti! Hai ragione su tutto, con un modulo che regola semplicemente i volt questi motori perdono coppia e senza carico aumenta comunque la velocità. L' argomento è molto interessante, se avessi le tue competenze tecniche ne costruirei uno!
Hello, i enjoyed your video. I am curious why we need external speed feedback from tach or optical disk. It seems to me that the speed feedback already exists in the current waveform of power supplied to the motor. There should be a positive or negative spike in the supply current each time a commutator segment make or breaks contact with the brushes. So it's like a built-in 6 or 8 or other number of pulse per rev (depending on pole count) speed feedback mechanism. I would like to build a device like the popular triac-based "router speed controller" which corded hand tools can be plugged into, that will deliver more consistent speed with changing load by compensating based on this feedback. But the fact it does not seem to exist and everyone (like manufacturers of washing machine motors you are using) opt for separate feedback mechanism. Why is that?
Hi, thank you for your comment. I have no definitive answer to your question but I think it's because spikes caused by the commutator are the core reason why DC brushed motors are noisy, and the reason why designers try to counteract it in various ways. Also AC mains can lead noise from other equipment. So picking these spikes could be unreliable and that's why some kind of external sensors are used to get speed feedback. Motor speed is affected by the internal resistance, so an alternative more reliable method is to use current compensation.
@@AccidentalScience great points! I had considered the noise generated by reading these spikes instead of suppressing them, but I had not considered the effect of noise from other devices on the line causing errors in the speed signal. Both issues could probably be addressed by the use of an isolation transformer with filtering on the primary, but this would be costly and grow complexity of the devices and is probably sufficient reason why the device I want does not already exist. Thank you for taking the time to address my questions!
You gave me a big idea sir , thank you, do you think it would be good for a lathe , what is the wattage of the motor how many rpm can go? while you trying to stop it looked very strong and the feedback keeping it to constant rpm was impressive, Thank you in advance.
Some of these kind of motors can go up to 10000 rpm, some even more. The real problem is to find the specifications. You can have a ballpark idea of the maximum attainable speed knowing that the spin phase in a washing machine usually is around 600 to 800 rpm, and looking at the diameter ratio of the belt wheel and the pinion of the motor you can calculate the max motor's rpm.
@@AccidentalScience Thank you for your reply, I think it should be good because I need my rpm's from 100 to 1000, so with a redaction of 10:1 will have plenty of torque. Basically I was thinking to use a vfd to drive my current motor, the problem is if I want to get range 100 to 1000 rpm I will need to drive the motor double the frequency or more, do you think there is a danger of exploding the motor at higher frequencies? thank you.
@@cytron8787 I haven't well understood what vfd have to do with universal motors that are those showcased in the video. AC induction motors have a specific speed rating that is given by their nominal frequency, say 50Hz. Some are specially built to handle higher frequencies, i.e., 400Hz, but that is not common. Unfortunately I have no that experience with vfd controlled motors so I cannot tell you whether a 50Hz motor could handle 400Hz, but under the mechanical point of view I am dubious about the ability of such kind of motor to run at ten times its rating speed: I wouldn't do it! Yes, a motor can also explode if it runs at a much higher speed. When I was young I heard a story from a fellow technician who fu*ed up the field parameters of a BIG DC motor (as tall as a man) which run away up to the explosion point, destroying a section of the building where it was installed and almost killing two men. Universal motors are usually rated for higher speed to work through a reduction and draw smaller current as they have poor heat dissipation and low efficiency when current goes high because of their field-winding configuration. Nevertheless motors coming from washing machines are pretty powerful and feature higher efficiency (for an universal motor) as their winding is thicker and have large brushes. Providing an external ventilation (i.e., through a computer fan and placing the motor in a proper case to convey the air flow) you can even squeeze quite a current through them. It's important to convey the air inside the motor as the rotor is the most critical part. Ciao.
@@AccidentalScience Thank you for the answer, I just want to run it 3 times of its rated rpm say from 50hz to 150hz, Really want to try it because it is much easer for me. I will take the risks , after all science it always risky :-).
Thank you for this video and all the rest, they're excellent. I subscribed as I'm also building a lathe. Also I have this exact motor. Do you have the circuit uploaded somewhere? I'm interested in tachometer input and the freq to voltage converter. Else: I don't have an oscilloscope in the same place than the motor, do you have a rough spec of the tachometer output? I mean amplitude vs speed and frequency vs speed.
If I recall correctly voltage should reach about 20V at max speed, while frequency should be proportional to the speed, in other words a peak per revolution. It is a sine wave, I think I've shown it in the video. About the schematic I will put it on my website, but in spite of the long time past I haven't completed the site yet 🙄
@@AccidentalScience Thank you! looking forward. Honestly your approach to the circuit design has so many good ideas and best practices that it would deserve a chapter on its own. It's modular, the feedback is PI, the high voltage section is well isolated... Oh, and also is NOT microcontroller based! rocks
@@EnriqueVetere thank you. Send me an email at info at my channel name com, be sure to add your username in the subject, I'll send you back the schematic.
@@EnriqueVetere I have received nothing. Please check the email address, the name must not have spaces in it. Alternatively go to my channel's page, click 'about' and 'contact for business' to reveal the email address. Please let me know, I have already had problems with that email in the past. Thank you.
I like all your projects (I follow the one from lathe very closely) Let's see if you can help me ... I have a washing machine motor, but I can't find any information about it. It has only 3 wires (it does not have brushes), apart from two of the plug, I measure the ohms and the 3 readings give me the same measurement, connect two terminals, it coiled and it got very hot. I have disassembled where the pins go and it has 3 coils, 6 tips ... And I don't know how to connect it ... Since if I can give you some information, it works 195v and 310hz ... The model is "Nidec wc107a50100" And if you could even guide me a little, I would appreciate it, thank you!
I was just going to sleep but at first glance (so to say) it seems you have a three phases motor. Did you googled for the motor's code? Any result? Maybe tomorrow I'll try to look fo it. Bye.
@@AccidentalScience I'm so sorry, it wasn't my intention If I have searched through google and nothing relevant, no datasheet or similar, it also gives me that feeling for certain reasons. Three phases to be able to be managed with an inverter of the washing machine itself, and the high frequency of the same motor, since if an inverter does not do it ... the local network cannot give those hz. I'm not a specialist .... Others say you can have two gears or two senses, but I doubt it. Thanks!
Don't worry, I was in bed watching videos when your comment popped up. I found this: www.indesitspares.co.uk/motor-nidec-sole-0016105900-type-wc107a50100-17500rpm/product.pl?pid=1692103 and I think it is your motor. This is a three phases motor (induction motor) with high frequency rate, as you noted 310Hz at 195V (AC), able to spin up to 17500 rpm ! Beautiful! The motor has a tachometer for speed feedback. Tacho comes from the two thin brown wires. I think it's a tacho and not an angle detector because only two wires come from the unit and AFAIK no angular sensor have only two wires. The other thicker colored wires are the power coils. To drive this motor you need an inverter. If the feedback was from a resolver (or a hall sensor) for angular sensing then the motor would have required a brushless driver. However I don't know any inverter that has a tacho feedback input (but not an expert on inverters here), so probably you really need the inverter from the washing machine where the motor came from, but that would be tricky. I also found a guy who did exactly what you're trying to do: recovering this kind of motor from a washing machine and rebuilding the circuit to drive it; follow this link: circuitcellar.com/research-design-hub/variable-frequency-drive-part-2/ Hope this will be helpful. Greetings from the Alps. P.s. Consider to subscribe and share, to help the channel growth. Thank you.
@@AccidentalScience Wowow! You've gotten more information in an hour than I have in weeks! I really couldn't find anything! I will try to make it work well with this information that you give me, I think the engine is worth it, I'll see that video! And yes, I am subscribed and I follow many of his videos, among them "Metal Lathe" which I think is a great job. Greetings from Complutum, Iberian Peninsula
I would say the main question is: "How did you controlled TWO such motors AT ONCE to power your lathe?" With one single such, or another controller, with two ... ? Why you did not used just TDA1085C which has all you needed for that application? But there would be the same question again - two motors at once?
TDA1085 is no longer in production, furthermore I have a bunch of OPAMPs so I rather use them than buying a specific component. Last but not least, TDA1085 do not provide insulation: all the circuit is at the power grid potential. About how I managed to control two motors at once: one of the motor is directly driven by a separate triac unit that work synchronous with the one that controls the main motor. The secondary motor has slightly higher speed than the main motor so it is forced to work as torque motor. More in a future video. Thanks for the questions.
@@AccidentalScience Thanks, you are really fast answerer, my respect! I bought 4 pieces TDA1085C recently easily. If particular separation from mains is required it can be done. I need now for my DIY combo lathe/mill, also to connect two motors to work as single one motor. I was not lucky to find two the same motors (can find two similar) - the same situation like your. Two triac's can be driven from single one controller, and connect Tacho from only one of the motors. For that case, I figured out just to make, and put adequately bigger pulley on the shaft of slower motor. Total torque should be the just the sum of both, but I am not sure about that at maximum load ... Thanks for Whitworth method video, and other nice ones. Posts about such smart stuffs are never enough, but unfortunately are rare. Care about places where you applied epoxy on your lathe. First, I wanted to make lathe bed from epoxy granite, but I was discouraged when heard from experienced machinists that metalworking machines sometimes became very hot, and epoxy become soft about 80 degree C ...
There are thousands ways to perform a function with electronic cirtuits. If you find in comfort with TDA1085, then go for it. I designed a circuit that has multple functions, not just motor control, so I used that one with a couple of power units built around a triac. That was designed around my needs and the components I have at home. That's why we do it by ourselves. I strongly doubt the bed of a machine reaches 80°C. Do you realize what kind of deformation would occur with such a temperature differential? Also electric motors typically have a thermostat that trips at 70°C, and encoders would just not work properly. If the bed of a lathe reaches 80°C, since it is the largest mass of the machine everything on the machine would level at that temperature. Lathes are subtractive working machines, which means they remove material, and most of the heat is removed through chips. If memory serve me well precision machines should sit between 30°C to 40°C and the most precise have temperature control of course. About this I've made a quick search, this is a problem that has been addressed since 1962, give a look at patent # US3303731A .
Controlling amplitude and frequency likely refers to AC induction motors, and not to Universal motors that essentially are DC motor with windings designed to have the right impedance when working at mains frequency. But, actually it would be possible to use a PWM circuit to control power amplitude (but not frequency) in place of a phase-fired control. While that kind of circuit would reduce the electrical noise and may show a better power factor (which can be close to 1 with a proper filter) and allows the motor to operate with slightly higher efficiency, it requires IGBTs or high voltage MOSFETs and the related driving circuit, making the power section much more complex and expensive. If memory serve me, Bosch and Renesas have developed an IC that do this job to control Universal motors and lights, but it is hard to source. TRIACs are easier to source and the circuit to control them is really simple. Thanks to all for commenting.
@@sqrt2-88 You're talking about VFD (variable frequency drives) or ESCs which change the frequency and in some cases the voltages. They do this by converting the AC to DC, producing a pulsed (frequency) PWM signal, and then running it through inverter to produce AC. There are two types of brushed motors, DC and universal. DC brushed motors run on DC and it's speed is controlled by the voltage. They can use PWM drivers or phase angle Triac drivers, but not ESCs or VFD without rectification. Universal brushed motors run on either AC or DC, so it's speed can be controlled by all VFDs, ESCs and PWM. Ideally, they run best on DC power. PWM controllers are superior to triac based ones because the current is constant while the voltage changes based on the duty cycle of the signal. Triacs work by "sampling" part of the AC signal at different phase angles. At low voltages, you get low current.
![How to reuse Washing Machine Motors [Arduino vs Basic Triac control]](/img/n.gif)
Thanks a lot, I surely learnt something. Would love to see more details about your electronics.
More to come. Thanks.
this is pretty smart
Nice detailed explanation - much better than the usual "connect it to a Chinese triac" videos, thank you. By the way, i love your accent and really appreciate you making your videos in English!
Thank you very much!
It should be interesting to control separately the stator and the rotor windings.
Universal motor can also be used as generator, such as in a wind generator, in such scenario, the separate control of the two windings should be very important to control the generated voltagy and the speed of the blades.
Indeed it would be interesting to seprately control the field and the rotor's current. But Universal motors have the stator's winding designed to widthstand high current, unlike classic DC motors with separated field excitation that use much less current to generate pretty strong magnetic fields. This could negatively affect the efficiency of the motor.
Just subscribed. I'm finding your video's much easier to follow than many on You Tube.
I've wanted to understand electronics for a long time, as a motorcycle tech I had basic understanding of electrical systems (charging and ignition, diodes, transistors and capacitors) but I'm retired now so can spend more time on learning about electronics.
Your not assuming things or 'talking down' to people who don't know this stuff (me 😄)
Are you an electronics lecturer/ tutor/ teacher/engineer?
Your whiteboard drawing are real good
Welcome!
Molto bravo complimenti! Hai ragione su tutto, con un modulo che regola semplicemente i volt questi motori perdono coppia e senza carico aumenta comunque la velocità. L' argomento è molto interessante, se avessi le tue competenze tecniche ne costruirei uno!
Grazie. I'll post the schematic and discuss the details in a future video.
I have a lot of them in my shop and always wondered, with the correct speed control pcb, can I use for of them to drive a small gokart?
Unless you bring with you a battery capable of supplying 300V with considerable wattage, you'd need a loonnnnnnnnnnnnnnnnnnnnnnnnng cable :)
Hello, i enjoyed your video. I am curious why we need external speed feedback from tach or optical disk. It seems to me that the speed feedback already exists in the current waveform of power supplied to the motor. There should be a positive or negative spike in the supply current each time a commutator segment make or breaks contact with the brushes. So it's like a built-in 6 or 8 or other number of pulse per rev (depending on pole count) speed feedback mechanism. I would like to build a device like the popular triac-based "router speed controller" which corded hand tools can be plugged into, that will deliver more consistent speed with changing load by compensating based on this feedback. But the fact it does not seem to exist and everyone (like manufacturers of washing machine motors you are using) opt for separate feedback mechanism. Why is that?
Hi, thank you for your comment. I have no definitive answer to your question but I think it's because spikes caused by the commutator are the core reason why DC brushed motors are noisy, and the reason why designers try to counteract it in various ways. Also AC mains can lead noise from other equipment. So picking these spikes could be unreliable and that's why some kind of external sensors are used to get speed feedback.
Motor speed is affected by the internal resistance, so an alternative more reliable method is to use current compensation.
@@AccidentalScience great points! I had considered the noise generated by reading these spikes instead of suppressing them, but I had not considered the effect of noise from other devices on the line causing errors in the speed signal. Both issues could probably be addressed by the use of an isolation transformer with filtering on the primary, but this would be costly and grow complexity of the devices and is probably sufficient reason why the device I want does not already exist. Thank you for taking the time to address my questions!
You gave me a big idea sir , thank you, do you think it would be good for a lathe , what is the wattage of the motor how many rpm can go? while you trying to stop it looked very strong and the feedback keeping it to constant rpm was impressive, Thank you in advance.
Some of these kind of motors can go up to 10000 rpm, some even more. The real problem is to find the specifications. You can have a ballpark idea of the maximum attainable speed knowing that the spin phase in a washing machine usually is around 600 to 800 rpm, and looking at the diameter ratio of the belt wheel and the pinion of the motor you can calculate the max motor's rpm.
@@AccidentalScience Thank you for your reply, I think it should be good because I need my rpm's from 100 to 1000, so with a redaction of 10:1 will have plenty of torque. Basically I was thinking to use a vfd to drive my current motor, the problem is if I want to get range 100 to 1000 rpm I will need to drive the motor double the frequency or more, do you think there is a danger of exploding the motor at higher frequencies? thank you.
@@cytron8787 I haven't well understood what vfd have to do with universal motors that are those showcased in the video. AC induction motors have a specific speed rating that is given by their nominal frequency, say 50Hz. Some are specially built to handle higher frequencies, i.e., 400Hz, but that is not common. Unfortunately I have no that experience with vfd controlled motors so I cannot tell you whether a 50Hz motor could handle 400Hz, but under the mechanical point of view I am dubious about the ability of such kind of motor to run at ten times its rating speed: I wouldn't do it! Yes, a motor can also explode if it runs at a much higher speed. When I was young I heard a story from a fellow technician who fu*ed up the field parameters of a BIG DC motor (as tall as a man) which run away up to the explosion point, destroying a section of the building where it was installed and almost killing two men. Universal motors are usually rated for higher speed to work through a reduction and draw smaller current as they have poor heat dissipation and low efficiency when current goes high because of their field-winding configuration. Nevertheless motors coming from washing machines are pretty powerful and feature higher efficiency (for an universal motor) as their winding is thicker and have large brushes. Providing an external ventilation (i.e., through a computer fan and placing the motor in a proper case to convey the air flow) you can even squeeze quite a current through them. It's important to convey the air inside the motor as the rotor is the most critical part. Ciao.
@@AccidentalScience Thank you for the answer, I just want to run it 3 times of its rated rpm say from 50hz to 150hz, Really want to try it because it is much easer for me. I will take the risks , after all science it always risky :-).
@@cytron8787 3 times more is not negligible but likely the motor won't explode ...however I won't take liabilities ;)
Thank you for this video and all the rest, they're excellent. I subscribed as I'm also building a lathe.
Also I have this exact motor.
Do you have the circuit uploaded somewhere? I'm interested in tachometer input and the freq to voltage converter.
Else: I don't have an oscilloscope in the same place than the motor, do you have a rough spec of the tachometer output? I mean amplitude vs speed and frequency vs speed.
If I recall correctly voltage should reach about 20V at max speed, while frequency should be proportional to the speed, in other words a peak per revolution. It is a sine wave, I think I've shown it in the video.
About the schematic I will put it on my website, but in spite of the long time past I haven't completed the site yet 🙄
@@AccidentalScience Thank you! looking forward. Honestly your approach to the circuit design has so many good ideas and best practices that it would deserve a chapter on its own. It's modular, the feedback is PI, the high voltage section is well isolated... Oh, and also is NOT microcontroller based! rocks
@@EnriqueVetere thank you. Send me an email at info at my channel name com, be sure to add your username in the subject, I'll send you back the schematic.
@@AccidentalScience mail sent! Thanks a lot
@@EnriqueVetere I have received nothing. Please check the email address, the name must not have spaces in it. Alternatively go to my channel's page, click 'about' and 'contact for business' to reveal the email address. Please let me know, I have already had problems with that email in the past. Thank you.
How can I remove the speed on it ?
What do you mean?
Hi. Have you uploaded somewhere the schematic already? Thanks.
I am updating my website, there you will find the schematics. Subscribe the newsletter to get notice when there will be new updates.
Ah ok, I was interested now. I want to build something similar.
@@worroSfOretsevraH I'll try to do my best but I can't give any certainty, both because of the heat and because I am busy with work.
I like all your projects (I follow the one from lathe very closely)
Let's see if you can help me ... I have a washing machine motor, but I can't find any information about it. It has only 3 wires (it does not have brushes), apart from two of the plug, I measure the ohms and the 3 readings give me the same measurement, connect two terminals, it coiled and it got very hot.
I have disassembled where the pins go and it has 3 coils, 6 tips ... And I don't know how to connect it ... Since if I can give you some information, it works 195v and 310hz ... The model is "Nidec wc107a50100"
And if you could even guide me a little, I would appreciate it, thank you!
I was just going to sleep but at first glance (so to say) it seems you have a three phases motor. Did you googled for the motor's code? Any result? Maybe tomorrow I'll try to look fo it. Bye.
@@AccidentalScience I'm so sorry, it wasn't my intention
If I have searched through google and nothing relevant, no datasheet or similar, it also gives me that feeling for certain reasons. Three phases to be able to be managed with an inverter of the washing machine itself, and the high frequency of the same motor, since if an inverter does not do it ... the local network cannot give those hz.
I'm not a specialist .... Others say you can have two gears or two senses, but I doubt it.
Thanks!
Don't worry, I was in bed watching videos when your comment popped up. I found this: www.indesitspares.co.uk/motor-nidec-sole-0016105900-type-wc107a50100-17500rpm/product.pl?pid=1692103 and I think it is your motor.
This is a three phases motor (induction motor) with high frequency rate, as you noted 310Hz at 195V (AC), able to spin up to 17500 rpm ! Beautiful! The motor has a tachometer for speed feedback. Tacho comes from the two thin brown wires. I think it's a tacho and not an angle detector because only two wires come from the unit and AFAIK no angular sensor have only two wires. The other thicker colored wires are the power coils. To drive this motor you need an inverter. If the feedback was from a resolver (or a hall sensor) for angular sensing then the motor would have required a brushless driver. However I don't know any inverter that has a tacho feedback input (but not an expert on inverters here), so probably you really need the inverter from the washing machine where the motor came from, but that would be tricky. I also found a guy who did exactly what you're trying to do: recovering this kind of motor from a washing machine and rebuilding the circuit to drive it; follow this link: circuitcellar.com/research-design-hub/variable-frequency-drive-part-2/
Hope this will be helpful. Greetings from the Alps.
P.s. Consider to subscribe and share, to help the channel growth. Thank you.
@@AccidentalScience Wowow! You've gotten more information in an hour than I have in weeks! I really couldn't find anything!
I will try to make it work well with this information that you give me, I think the engine is worth it, I'll see that video!
And yes, I am subscribed and I follow many of his videos, among them "Metal Lathe" which I think is a great job.
Greetings from Complutum, Iberian Peninsula
I would say the main question is: "How did you controlled TWO such motors AT ONCE to power your lathe?" With one single such, or another controller, with two ... ? Why you did not used just TDA1085C which has all you needed for that application? But there would be the same question again - two motors at once?
TDA1085 is no longer in production, furthermore I have a bunch of OPAMPs so I rather use them than buying a specific component. Last but not least, TDA1085 do not provide insulation: all the circuit is at the power grid potential.
About how I managed to control two motors at once: one of the motor is directly driven by a separate triac unit that work synchronous with the one that controls the main motor. The secondary motor has slightly higher speed than the main motor so it is forced to work as torque motor. More in a future video. Thanks for the questions.
@@AccidentalScience Thanks, you are really fast answerer, my respect! I bought 4 pieces TDA1085C recently easily. If particular separation from mains is required it can be done. I need now for my DIY combo lathe/mill, also to connect two motors to work as single one motor. I was not lucky to find two the same motors (can find two similar) - the same situation like your. Two triac's can be driven from single one controller, and connect Tacho from only one of the motors. For that case, I figured out just to make, and put adequately bigger pulley on the shaft of slower motor. Total torque should be the just the sum of both, but I am not sure about that at maximum load ... Thanks for Whitworth method video, and other nice ones. Posts about such smart stuffs are never enough, but unfortunately are rare. Care about places where you applied epoxy on your lathe. First, I wanted to make lathe bed from epoxy granite, but I was discouraged when heard from experienced machinists that metalworking machines sometimes became very hot, and epoxy become soft about 80 degree C ...
There are thousands ways to perform a function with electronic cirtuits. If you find in comfort with TDA1085, then go for it. I designed a circuit that has multple functions, not just motor control, so I used that one with a couple of power units built around a triac. That was designed around my needs and the components I have at home. That's why we do it by ourselves.
I strongly doubt the bed of a machine reaches 80°C. Do you realize what kind of deformation would occur with such a temperature differential? Also electric motors typically have a thermostat that trips at 70°C, and encoders would just not work properly. If the bed of a lathe reaches 80°C, since it is the largest mass of the machine everything on the machine would level at that temperature. Lathes are subtractive working machines, which means they remove material, and most of the heat is removed through chips. If memory serve me well precision machines should sit between 30°C to 40°C and the most precise have temperature control of course. About this I've made a quick search, this is a problem that has been addressed since 1962, give a look at patent # US3303731A .
I have one like the one you have but the one I have doesn't have braces
Why not a pwm circuit where you can control amplitude and frequency.
Because these are universal motors running from mains AC. That means fixed amplitude (240v) and frequency (50Hz).
that is used to control brushless / asynchronous motors, not brushed motors
Controlling amplitude and frequency likely refers to AC induction motors, and not to Universal motors that essentially are DC motor with windings designed to have the right impedance when working at mains frequency.
But, actually it would be possible to use a PWM circuit to control power amplitude (but not frequency) in place of a phase-fired control. While that kind of circuit would reduce the electrical noise and may show a better power factor (which can be close to 1 with a proper filter) and allows the motor to operate with slightly higher efficiency, it requires IGBTs or high voltage MOSFETs and the related driving circuit, making the power section much more complex and expensive. If memory serve me, Bosch and Renesas have developed an IC that do this job to control Universal motors and lights, but it is hard to source. TRIACs are easier to source and the circuit to control them is really simple.
Thanks to all for commenting.
@@sqrt2-88 You're talking about VFD (variable frequency drives) or ESCs which change the frequency and in some cases the voltages. They do this by converting the AC to DC, producing a pulsed (frequency) PWM signal, and then running it through inverter to produce AC.
There are two types of brushed motors, DC and universal. DC brushed motors run on DC and it's speed is controlled by the voltage. They can use PWM drivers or phase angle Triac drivers, but not ESCs or VFD without rectification.
Universal brushed motors run on either AC or DC, so it's speed can be controlled by all VFDs, ESCs and PWM. Ideally, they run best on DC power.
PWM controllers are superior to triac based ones because the current is constant while the voltage changes based on the duty cycle of the signal. Triacs work by "sampling" part of the AC signal at different phase angles. At low voltages, you get low current.
A vfd would be the best bet for speed control
🙏🌹🌟🌟🌟🌟🌟🌟🌟