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RE: [TCML] homebrew VFD?
a VFD putting out a square wave will do really nasty things to a motor or transformer - and you are working really hard to do what you can buy cheaper - for example, I have some small VFDs that are 440V input, so they are hard to sell to a home hobby person - I got them inadvertently - instead of making a VFD, you could just step your 110 up to 440 and use one of these things and get all the nice features of a VFD such as torque control and full RPM from near zero to > 60 hz (you can find the units on my web site, wbnoble.com). Small 3 phase motors are cheap, when you get them used, and 440V ones are even cheaper so my recommendation would be to use a true 3 phase motor and a real VFD.
> Date: Mon, 10 May 2010 14:27:40 -0700
> From: yurtle_t@xxxxxxxxx
> Subject: Re: [TCML] homebrew VFD?
> To: tesla@xxxxxxxxxx
>
> I assume you're trying to make a single phase VFD. I ran a single phase motor from a 3 phase vfd by disabling it's phase imbalance monitoring. It worked OK up to a point. If I ran it too slow, the motor's internal centrifugal switch started disengaging. I considered adjusting the weights, so it would engage at a lower speed, but ended up buying a 3 phase motor. My smaller sync motor doesn't have this switch, so I'm sure it would have worked just fine.
>
> Adam
>
> --- On Mon, 5/10/10, Scott Bogard <sdbogard@xxxxxxxxx> wrote:
>
> > From: Scott Bogard <sdbogard@xxxxxxxxx>
> > Subject: [TCML] homebrew VFD?
> > To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> > Date: Monday, May 10, 2010, 1:34 PM
> > Greetings all,
> > While my intentions with this are
> > completely off topic, the information could be extremely
> > helpful for those running asynchronous rotaries, and I know
> > of nobody else to ask this question, thus I fell no guilt
> > putting it here. I want to know if it is possible to
> > essentially build a variable frequency drive, this is what I
> > had in mind. Get a mot, remove the windings then make
> > your own to take 36V to 120V. Drive the primary with a
> > variable flyback type inverter, designed for 1-120 Hz.
> > So we have a DC square wave entering the primary. On
> > the secondary put a capacitor sized to take a square wave
> > and make it nearly sinusoidal (so perhaps a cap resonate
> > with about 90 Hz?). And then feed your secondary into
> > your induction motor winding. It seems to make sense
> > in my head but it seems a bit too simple, perhaps the square
> > wave will not really drive the mot core correctly because of
> > saturation in which case I don't know what to do. Any
> > thoughts or should I just abandon this.
> >
> > Scott Bogard.
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> >
>
>
>
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