High Voltage Condition

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claus

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I have got a situation in a plant where VFD's have been tripping off due to high voltage. 521 volts was measured at the VFD's. The VFD's were originally set at 460 volt and the high limit raised up to 480 volt with 10% allowance. We are having the utility change the taps on the transformer down to 500V at the secondary of the transformer. (I am not sure why we cannot reduce down to the 480V and have to ask the utility).

Question: Is there a negative effect of running motors, compressors, HID ballasts, UPS's on a voltage +5%?
 
Re: High Voltage Condition

The utility should be able to get the voltage to 480 volts. They may have their sub regulator setting too high.
 
Re: High Voltage Condition

In large industrial plants it is not unusual for voltages to exceed 515 volts on a 480 nominal system (528 is +10%) - that is why I always install isolation transformers for VFD drives and buck the voltage down to a level at or below 480 (470 is a good input voltage) - that way when the system voltage is high due to low load, or caps being switched off, then the drive input will be below 500 - another option is to connect "Dynamic Brake" resistor modules to the DC buss of the VFD - this will shunt energy off the DC buss & keep the drive from tripping on buss over-voltage. Also not all drives are equal, some have more built in features to help on high buss issues, or even higher rated components.
 
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