VFD failure

[MTW]

Some excellent free advice, take it and USE IT.
For your open transition wye delta starters, you may want to look into closed transition switching starters, I have read that the transition spikes can be substantially reduced with the resistors that they provide, if you can fit them into your equipment enclosures.

 

[kwired]

Some excellent free advice, take it and USE IT.
For your open transition wye delta starters, you may want to look into closed transition switching starters, I have read that the transition spikes can be substantially reduced with the resistors that they provide, if you can fit them into your equipment enclosures.

Or replace them with VFD's or soft starters?

 

[retirede]

Or replace them with VFD's or soft starters?

I’d do that long before I’d spend money on a new closed-transition (or other electro mechanical) starter.

 

[GeorgeB]

Do you think a separate stand alone Line reactor would prevent the transients from the wye/delta starters?

Prevent transients, almost impossible; reduce levels and energy so as to minimize damage to input circuitry, probably. We've got @Jraef in here who seems to know as much about drives as the rest of the thousands of us combined and that seems to be his thought.

 

[Rsteenson]

Thank you all again! I really appreciate you taking the time to analyze and respond.

 

[__dan]

Looking at a least cost scenario, my guess would be that line side line reactors and the drive are not all going to fit inside the MCC bucket. There's also an issue of modifying an MCC bucket in the field and not by the manufacturer.

That would indicate external remote mounting everything and using the MCC just for the power tap, back to the bucket with a breaker or fuses.

The line reactor will drop Voltage rather than pass current for fast transients much faster than a 60 cycle sinewave. The inductance of the line reactor, L, E = L di / dt. E, the drop through the line reactor, increases with di / dt, the change in current per unit infinitesimal time.

Then the SPD would go after the line reactor, with the caveat that it would do nothing for transients upstream of the line reactor. That's if you wanted to keep the existing Y delta starters and not spend money there. Tap the MCC for power, then line reactors, then SPD's, then, for multiple drives you could go to a breaker panel or fused switchboard and power the drives from there. The line reactors could be sized large enough for all the downstream necessary drives instead of one set for each.

 

[synchro]

... We have had two Square D Altivar VFD's blow up on the same motor in a month. Square D hasn't even gotten back to me with any advice or suggestions on where to go from here. ... This is the only VFD that comes out of this electrical room that has about a 50-60 motor MCC.

I concur with _dan and Jraef that putting a dedicated reactor ahead of the problem VFD would be appropriate in this situtation.
Also, I think it would be wise to put a SPD after this reactor so that you're not putting the entire burden of shunting surge currents on internal SPD within the VFD.

If you really wanted the best protection, at the risk of going overboard you might consider having a cascade of a reactor, a SPD to clamp the surge voltage, and another reactor to limit any remaining surge currents that could enter the VFD and damage it. The impedance of the reactors would be chosen to achieve the best compromise between surge protection and voltage drop.

 

[Jraef]

Or… get rid of the Wye-Delta starters and replace them with soft starts.