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Pesky "Overvoltage" Warnings in Servo Drive

I had a problem with a number of servo drives shutting down due to "Over Voltage" warnings that I finally solved. As it turns out, there are several ways to approach the issue but I only tried two methods before I was successful. While investigating, I realized that the servo drives could not measure the incoming AC voltage, it could only measure the captured DC voltage. Then it calculated the apparent AC voltage and freaked out. I was apparently capturing enough peak energy to raise the DC voltage above the maximum threshold for operation.

The first approach involved the installation of Line Reactors and in some cases, it worked. Unfortunately, I still had shutdowns after midnight even though the incoming AC was within its 10% tolerance level. Input voltage was 3 phase, 480 V, 60 Hz. The shutdowns were infrequent, but very annoying.

Since I couldn't adjust the software settings for the supply voltage any higher, I finally realized that the next logical step was to reduce the voltage rather than trace down all of the existing or future harmonic contributors on the same substation.

I considered resetting the taps on the substation but it would have been an expensive and risky approach since other equipment might be negatively affected by the reduced supply voltage. I also knew that I had some harmonics loose in the substation but I wasn't about to spend the money it would have taken to squash the harmonics.

Finally, I bought step-down transformers that were rated to operate as autotransformer's. By feeding the AC supply to all coils in series, I could take off a reduced voltage on the primary coils (also in series) and I've not had any other problems since. My only question was whether or not I skipped an approach that would have saved me some money.

I had 10 Servo Drives on the same substation, so it took 30 transformers to solve the problem at about $95 per transformer. Total cost (not including labor) was about $950.

My question is this: Could I have done something less expensive and had as good of a result? I think the answer is NO.