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Greetings guys,

I've been following the "reactor" thread with some interest.? I too have been using a VFD (TECO FM50)? for circa 2 decades on a Maximat 7.
I appreciate that my experience does not apply to all.? Also I understand that these motors have different histories, and in fact fail without
the help of a VFD.???? BTW, mine runs cool as a clam on the VFD and that was not the case while using the capacitor hack to approximate 3 phase.

One factor that appeared to be missing from this thread is an honest to goodness measurement of the the VFD driving the motor.
I'm a retired EE that worked as a development engineer in the Test and Measurement world for over 30 years.
To this end, a 180:1 differential voltage measurement adapter was created to drive a LeCroy 9350AM O'Scope under HPIB control
and interfaced to MATLAB.

Here are some results .......? I sure hope the screen shots come through !

1)? This one is very telling. The YELLOW is the raw voltage across one phase of the the FM50:

Note that peaks approach 500V. Also note that the resemblance to a sine wave is coincidental.
But pass this waveform through a low pass filter, and behold ... a pretty darn nice sine wave is produced !
Also, the (standard) 208V phase voltage should produce peaks of sqrt(2)*208 = 294V and the above (low passed data) is mighty close (285V) even with the "flat topping".?
Zooming in:

You can see that what appears to be some high frequency hash is actually a sequence of variable duration pulses that "fine tune" the larger steps in the FM50 output.
Pretty clever.?

As for me, no filtering need be applied. If these voltages break down the motor's wire insulation, that was probably going to happen VFD or no VFD.
Your mileage may vary !!!

Best regards from N. CA.

Dick?
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