Line current three phase motor in six step commutation

AI Thread Summary
The discussion focuses on measuring line current in a three-phase motor controlled by six-step commutation. The user observes an asymmetrical current waveform, with measurements showing 3.1A and -4.1A instead of the expected symmetrical values of 3.1A and -3.1A. Concerns are raised about potential spikes in the current signal, particularly the -4A reading, which may indicate issues with the motor's performance. Suggestions include checking for bad soldering in the drive as a possible cause of the irregularities. The conversation highlights the importance of ensuring proper connections and soldering to maintain consistent current readings.
Trainee28
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Hello,

I have got a three phase motor connected in delta that is controlled in six step commutation. When I measure the line current of one of the phase under oscilloscope, I got something like this :
upload_2015-6-18_13-58-52.png


Can anyone tell me why the amplitude of the current isn't 3.1A and -3.1A? What I got here is 3.1A and -4.1A which is not symetrical.
 
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I'm worried about the spikes when the signal = -4A. Could be that it is trying to come up with -3.1A, but it cannot ( connection lost again ).

Bad soldering in your drive?
 
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