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Running AC induction motors from pulsed DC

Started by Julian Barnes April 15, 2016
Hi all,

Is it possible to power an 50Hz or 60Hz single phase AC induction 
(asynchronous) motor from some form of pulsed DC - say like PWM or some 
variant thereof?

Thanks.
On Friday, April 15, 2016 at 5:11:30 PM UTC-7, Julian Barnes wrote:

 
> Is it possible to power an 50Hz or 60Hz single phase AC induction > (asynchronous) motor from some form of pulsed DC - say like PWM or some > variant thereof?
Universal motors, yes (these usually have brushes visible, and aren't necessarily near a multiple of 1800 RPM). AC induction motors, with only two wires, no (unless you include polarity-switching in addition to pulsing). Some induction motors (3-phase or similar) with more than two wires, you can drive with (more than one) pulsed DC source.
On Sat, 16 Apr 2016 00:08:04 +0000, Julian Barnes wrote:

> Hi all, > > Is it possible to power an 50Hz or 60Hz single phase AC induction > (asynchronous) motor from some form of pulsed DC - say like PWM or some > variant thereof? > > Thanks.
I'm not sure what you're thinking of trying, but in principle one could PWM DC such that it's a bunch of high frequency stuff riding on 60Hz 120VAC. In that event the motor would filter out the high frequency stuff and run on the 60 stuff. Now that we've discussed the bark on the tree, could you step back a bit and tell us about the forest you want to get through? -- www.wescottdesign.com
On Fri, 15 Apr 2016 21:45:29 -0500, Tim Wescott wrote:

> I'm not sure what you're thinking of trying, but in principle one could > PWM DC such that it's a bunch of high frequency stuff riding on 60Hz > 120VAC. In that event the motor would filter out the high frequency > stuff and run on the 60 stuff.
Flipping the polarity of the pulses as whit3rd suggested seems a somewhat more dependable method.
> Now that we've discussed the bark on the tree, could you step back a bit > and tell us about the forest you want to get through?
Perhaps. But first answer me this: if a tree falls over in this forest of yours and no one is present, does it make a sound?
On Fri, 15 Apr 2016 21:45:29 -0500, Tim Wescott wrote:

[...]

Oh BTW I found your essay on PID controllers very useful; thanks for 
contributing it. >:-}
On Sat, 16 Apr 2016 09:27:06 -0000 (UTC), Julian Barnes
<jb9889@notformail.com> Gave us:

>On Fri, 15 Apr 2016 21:45:29 -0500, Tim Wescott wrote: > >> I'm not sure what you're thinking of trying, but in principle one could >> PWM DC such that it's a bunch of high frequency stuff riding on 60Hz >> 120VAC. In that event the motor would filter out the high frequency >> stuff and run on the 60 stuff. > >Flipping the polarity of the pulses as whit3rd suggested seems a somewhat >more dependable method. >
Two synched PWMs on the same line with one creating the negative pulses and one creating the positive pulses 180 degrees out of phase with each other. But there is a lot of wasted energy, and no need to do it when there are DC motors out there that are far more efficient.
>> Now that we've discussed the bark on the tree, could you step back a bit >> and tell us about the forest you want to get through? > >Perhaps. But first answer me this: if a tree falls over in this forest of >yours and no one is present, does it make a sound?
Could you be any more retarded?
On Sat, 16 Apr 2016 06:47:29 -0400, DecadentLinuxUserNumeroUno wrote:

> Could you be any more retarded?
When it comes to retardedness, you would know. You're the expert.
On Sat, 16 Apr 2016 00:08:04 -0000 (UTC), Julian Barnes
<jb9889@notformail.com> wrote:

>Hi all, > >Is it possible to power an 50Hz or 60Hz single phase AC induction >(asynchronous) motor from some form of pulsed DC - say like PWM or some >variant thereof? > >Thanks.
A full H-bridge perhaps. Depends of the available DC voltage and the AC motor voltage (Vrms) ratings.
On Sat, 16 Apr 2016 12:31:34 -0000 (UTC), Julian Barnes
<jb9889@notformail.com> Gave us:

>On Sat, 16 Apr 2016 06:47:29 -0400, DecadentLinuxUserNumeroUno wrote: > >> Could you be any more retarded? > >When it comes to retardedness, you would know. You're the expert.
Says the idiot who does not know what sound is.
On Saturday, April 16, 2016 at 8:47:40 PM UTC+10, DecadentLinuxUserNumeroUno wrote:
> On Sat, 16 Apr 2016 09:27:06 -0000 (UTC), Julian Barnes > <jb9889@notformail.com> Gave us: > >On Fri, 15 Apr 2016 21:45:29 -0500, Tim Wescott wrote: > > > >Flipping the polarity of the pulses as whit3rd suggested seems a somewhat > >more dependable method. > > > Two synched PWMs on the same line with one creating the negative > pulses and one creating the positive pulses 180 degrees out of phase > with each other. But there is a lot of wasted energy, and no need to do > it when there are DC motors out there that are far more efficient.
I don't see where the energy is being wasted. The difference between DC motors and synchronous/stepper-motors is how you switch the current through the drive coils - the same currents do the same job. You can set up inefficient drive schemes for both sorts of motors, but neither is intrinsically more efficient than the other. <snipped time-wasting abuse - Julian Barnes is a right-wing nitwit - which doesn't actually mean that he's retarded, because at least some of them ignore evidence they don't like, rather than being too dumb to understand it's implications.> -- Bill Sloman, Sydney