400 Hz

[Jon Elson]

On 05/05/2021 10:37 AM, Paul Koning via cctalk wrote:
> Incidentally, a way to get three phase power at a 
> frequency of your choice is to use a "variable frequency 
> drive". That's basically a high power solid state inverter 
> intended to drive three-phase motors with a chosen 
> frequency resulting in the RPM of your choice. Depending 
> on the model, those can go up to 120 Hz or so, or all the 
> way to somewhere around 400 Hz. I have a very cheap one at 
> home that runs on single phase 220 volt power, producing 
> up to 3 kW or so at anywhere up to 120 Hz. (Made by a 
> company named Teco, amusingly.) Most of these and 
> especially the larger ones want three phase mains input, 
> though I'm told that even for those you can typically just 
> connect them to single phase power (between two of the 
> three inputs, leaving the third unconnected) at reduced 
> power ratings. These devices are surprisingly cheap, in 
> particular they tend to be cheaper than "rotary phase 
> converters" which is how machine shops traditionally 
> produce three phase power when their mains is just single 
> phase. paul 
Note that VFDs are designed to run motors exclusively.  They 
approximate a sine wave with pulse width modulated 400 V 
pulses. DON'T EVER try to run electronic gear with a VFD, at 
least without a massive smoothing filter to convert to a 
true sine wave.  With a motor, the winding inductance solves 
the problem, and the coils see nice sine-wave currents.

Jon