RE: [TCML] speeding up sync motors ?

[Yurtle Turtle <yurtle_t@xxxxxxxxx>]

I run my 3 phase 60 Hz inverter rated motor at up to
150 Hz with my VFD with no problem. It's such a low
duty cycle it doesn't seem to care. Even last
Halloween, I doubt any particular run went longer than
30 seconds.

At work, the only problem we've seen with running
non-inverter rated motors with VFD's is slower speeds,
where they can't self cool adequately. We've been
known to rev a 60 Hz motor up to 66 Hz, as a cheap
upgrade. We only do that to inverter rated motors
though. Of course, running them at twice the speed
they were designed for continuously will definitely
affect bearing life, and may cause other damage.

As to doing so with a single phase sync motor, I was
able to achieve moderate speed control with mine,
though the speed switch would drop out if I went too
slow, and I'd get errors on my VFD if I went too high.
I don't recall the full range of RPM I got, but I was
feeding it from phase to phase of a three phase VFD.
If I recall, I had to program it to ignore non-life
threatening alarms, such as phase imballance. I ended
getting a three phase inverter rated motor and
everything's happy now.

Adam

--- S&JY <youngs@xxxxxxxxx> wrote:

> Chris,
> 
> A few have reported they run their SRSGs with
> variable frequency drives.
> But with most electric motors, the range of RPM that
> can be achieved without
> losing sync or overheating the motor is limited. 
> You might get a 60 Hz
> motor to work reliably at 40 to 90 Hz, but not 400
> Hz.
> 
> You could experiment with a variable frequency sine
> wave oscillator driving
> a hefty audio amplifier (capable of several hundred
> watts rms) driving a
> beefy 6 volt filament transformer run backwards to
> step up the voltage to
> 120, and drive a small motor, e.g. 1/4 or 1/3 Hp.
> 
> But why not do as Dr. Resonance suggests and belt
> drive your RSG to step up
> or down the RPM by varying the pulley sizes?
> 
> --Steve Y. 
> 
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx
> [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
> Of Chris Swinson
> Sent: Thursday, November 22, 2007 11:59 AM
> To: Tesla Coil Mailing List
> Subject: [TCML] speeding up sync motors ?
> 
> Hi all,
> 
> Wonder if anyone has tried to speed up sync motors
> by using a higher 
> frequency (maybe 200 or 400hz)...  Options for this
> are either a 400hz 
> generator, or hack a regular DC to AC inverter to
> run at 400hz.... Just 
> pondering really!
> 
> Cheers,
> Chris
> 
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
> 



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