Yaskawa VFD issues

[lonboy]

We recently installed 2 Yaskawa e7 drives for a couple of fan coil supply fans conditioning a post production facility. About every 2 weeks or so, both drives go off on DC bus overvoltage which can only happen if the DC bus reaches 850 VDC. After resetting the drives, I checked the DC bus and it's running around 650 VDC. Supply voltage when measured with a standard meter is 485 volts AC and my RMS meter measures 550 volts AC. Talked to the utility and they said to not pay attention to the RMS reading. Both drives are set to a fixed speed. When I shut the drives down, the RMS reading on the supply voltage goes down to 485 volts. I talked to the Yaskawa support people and they said there is no way that the drive operation could contribute to an increase of voltage on the supply side. Next step is to install a data log on the 480V supply to see if we're getting voltage spikes from the utility.

Does anyone have any experience with these issues?

Cheers,
lb

[Balibe]

The drive is rated for a max voltage of 528vac. I would be sure on the supply voltage. Maybe check it at the service disconnect or electrical panel while it is running. With the 2 reading so far apart, a 3rd meter wouldnt hurt just to be sure.

Fixed Speed but do the run 24/7?

How are you stopping the Fans .... Ramp, Coast or Braking? If you are ramping, what is the Decel Time? If the fans are large, your issue could be with stopping them. Stop the VFD's normally and monitor the DC Bus Voltage to see what you get.

Normally I set AHU fans to 60sec accel/decel and coast to stop.

[lonboy]

Fans are running 24/7. Speed is constant. Decell time is 120 seconds. I suspect voltage spikes from Edison. I've got an iLON100 on the job and the data log showed that the first one happened at 12:01 on New Years Eve (static went to 0). This morning it happened at 6:00AM just about the time that all of the street lights turned off in the neighborhood. I've seen RMS voltage as high as 600V and the drive keeps on running. Maybe some lurking sparkie can illuminate me on the true meaning of EMF.

What'ya think about sticking a voltage monitor on the panel and logging the voltage? Do you know of a good/inexpensive voltage transducer that can output a 0-10 or 4-20? I'm still a little confused with the RMS reading. Wait a minute, what was I thinking? Yaskawa has a LON board option for less than $200! Maybe there's a network variable that will give me a clue.

lb