Power Analysis

[Danny M]

I am trying to develop a 3 phase power analyser to determine the output torque. I have found suitable voltage and current sensors and interfaced them to LabVIEW. The current waveform is sinusiodal but the voltage waveform is much more complex. Because the motor is driven by a switch mode variable speed drive, the voltage waveform across the motor is made up of many small pulses and is not sinusodal, it is atually a PWM(Pulse Width Modulated) square wave. I have perfomed a FFT frequency analysis and can see the fundumental and its harmonics, butb does anyone know how to proccess this waveform and determine the voltage accros the motor?

[MattP]

Hi Danny,

My expertise is in LabVIEW, and not 3-phase induction motors, but perhaps if you can give me some details on what type of processing you'd like to perform I can recommend a course of action in LabVIEW.  Specifically, what kind of processing are you looking to perform on the voltage signal?  You're looking for the voltage across the motor, but are you looking for an instantaneous value, a predictive model for the future voltage values, an average voltage over a time window, an RMS value at a given time, etc?  Can you refer me to the necessary equations to calculate the output torque of the motor?