Inverter: Measurement of motor voltage and motor current by means of oscilloscope

Question:
Can the motor voltage and current be correctly determined using an oscilloscope at the output of the inverter?

Answer:
  • Motor voltage:
    Yes, the instantaneous value of the voltage output by the inverter between the motor phases can be determined with the oscilloscope.
    The oscilloscope image below left shows the pulse-width modulated voltage curve at the inverter output.
    If using a meter, it is recommended to use a moving iron meter to measure the RMS value.

  • Motor current:
    Yes, the instantaneous value of the motor current can be determined with the oscilloscope.
    On the oscilloscope picture below right, the sinusoidal course of the motor current can be seen, which is due to the motor voltage and the connected motor (inductance).
    To measure the r.m.s. value, it is advisable to use a moving iron meter.




Tip: Lenze drive controllers have parameters for displaying the effective values of motor voltage and motor current:
  • Predecessor device series: code positions C0052 and C0053
  • Current device series:      Index 0x2D82 and 0x2DD1:5 

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AKB-ID: 200400400
Last update: 2024/01/11
Category: FAQ, Tips and Tricks

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