Please help with constant VF motor driver

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DELTA67

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Hi all,
I have successfully simulated this VFD driver:

GitHub - carneeki/OpenVFD: Variable Frequency Drive for ATmega328 based Arduinos

Variable Frequency Drive for ATmega328 based Arduinos - GitHub - carneeki/OpenVFD: Variable Frequency Drive for ATmega328 based Arduinos
github.com

How to add constant VF option please if the motor is rated 230V, 50Hz?
I know that I need to scale the values in the lookup table, but how?
Another question, if I change the PWM carrier frequency from 31kHz to 8kHz, Have I to use another lookup table? How to generate it?
Many thanks in advance.
 

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BradtheRad said:
to filter SPWM pulses at the final stage as dependent on load and frequency. It may be necessary for you to test different LC values (in the 2nd-order low-pass filter) in order discover what circumstances require which values (and/or L:C ratio).
Click to expand...

Thanks Bradtherad for your contribution in the thread.
The inherent LR filter load representing the motor will "convert" the SPWM into a pure sinodal electric signal.
the motor acts as a low pass filter. The inductance and resistance of the coils windings create a low pass RL filter. Further, the inertia of the rotor and load creates a mechanical low pass filter.
--- Updated ---

FvM said:
A VFD however can't run with constant V/F above rated motor frequency without either using a higher input respectively DC link voltage or rewiring the motor from wye to delta (if not already delta wired).
Click to expand...
I think it runs faster but with less torque, no?
How to implement overmodulation?
 

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