How far is the motor from the VFD? How far is the VFD from the source?
Source to Panel is about 50m, VFD to Motor is 5m. Voltage is to keep a single voltage in control cabinet, 600VAC is for two 30hp pumps.
Power comes from electrical room through a disconnect, circuit breaker, and line reactor to the VFD.
If the VFD suddenly stops pulling current, could the line reactor be giving the VFD input an inductive kick?
Possible I guess however when motor is stopped, VFD still drawing small current for itself. Seems unlikely though.
What regulations is the VFD rated for? In particular, high-line and surge ratings would be of interest?
Tim
Unit is AutomationDirect GS2-53P0, there isn't much more in the manual, just the 5kA @600VAC short circuit withstand rating.
I was contemplating using my DS1054 and a B&K PR2000B high voltage probe, setting up a pass/fail envelope test and letting it run.
Can this be done safely or am I suicidal for even thinking of doing this?
Any other economical ways of measuring/logging this?
No, don't use this kind of probe for this kind of circuit. You'd want a differential probe rated at 600Vrms CAT IV here.
Any other economical ways of measuring/logging this?
If you know what you're doing, one could build a series connected resistor string to safely divide the voltage down to the scope's input level, and use two channels in subtract mode.
Otherwise, no.
Your symptom description clearly points to line overvoltage / surge, but I've also seen input rectifiers been destroyed by (otherwise mostly harmless) bursts. Once a single rectifier diode fails, the vast amount of available energy at the input takes care of blowing the stuff up.
One reason for surge / burst might me other consumers (the 30hp pumps you mentioned) connected to the same circuit. Not while they're running, but rather at turn-on or turn-off.
Any additional way to protect this from these possible bursts?
I'm going to be doing an autopsy on the failed unit, try to find out exactly what the sequence of events was.
As for logging the line voltages, differential probes aren't cheap, I may just buy something like a Fluke 376FC and log a phase at a time.
Will keep you posted, Thanks for the help