rockman7892
Electrical
I have 2 480V Siemens MM440 VFD's which I have discussed on this forumn previously. I have an issue with both of these drives tripping on a DC Bus Overvoltage when these drives are not running but rather are just sitting idle. The only thing that can cause these drives to trip on overvoltage while sitting idle would be a voltage spike or fluculation on the line side of the drive. I'm assuming that a voltage spike of a certain amount will cause the DC bus link to go high and thus trip the drive on an overvoltage condition.
I have set up a power monitor to try and capture some of these events. However when I see that drive is tripped and then check power meter I see nothing on the power meter. I suspect that since the power meter (Fluke 1735) is only capable of capturing events longer than a half cycle (8.3ms) then it is possible the voltage spikes are happening too quickly for the meter to capture. I have done some research and saw that these voltage spikes are usually very quick and in the order of .5m - 2ms which would be much too quick to capture wih my meter. Would a voltage spike this quick be enough to cause the DC bus to go high and trip the drive?
I would suspect that if these drives were tripping on an overvoltage condition as a result of a transient then I would see other drives througout the plant on the same distribution system trip as well for the same reason. I do not see this happening. Of course this is assuming the transient is coming from the utiltiy or somwhere up in the plant. These drives are by far located at the furtherst point on the distribution system. Does this furthest distance have anything to do with only these drives tripping?