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Motor troubleshooting

Charlie Owen, Virginia

A 200 hp DC motor was consistently overheating. It sounded 'graunchy' to me so I displayed the armature current waveform using my ScopeMeter 123 with my Fluke ac/dc current probe. It was immediately obvious that at startup two years earlier, the machine vendor had not tuned the current loop. I used the drive manufacturer's instructions to tune the loop and documented the 'before' and 'after' armature current waveforms with Fluke View software. Due to the improved form factor of the tuned armature current, the motor has been running cool for the last two years and the plant electrician ordered a 123, Fluke view and a current probe for himself!