RCD protection of small VSDs

[Bruce Varley]

We have some small (around 1KW) 3-phase VSDs with residual current
devices on the inputs, and the RCDs are tripping intermittently. We
don't believe there really is earth leakage, the equipment is new and
reputable, and the problem occurs across several devices. Is this a
situation that's known to result in spurious trips, I can envisage that
high harmonic content in the input waveform could cause it. Has anyone
encountered this problem and solved it?

 

On Wednesday, 1 August 2012 19:28:01 UTC+10, Bruce Varley wrote:

We have some small (around 1KW) 3-phase VSDs with residual current

devices on the inputs, and the RCDs are tripping intermittently. We

don't believe there really is earth leakage, the equipment is new and

reputable, and the problem occurs across several devices. Is this a

situation that's known to result in spurious trips, I can envisage that

high harmonic content in the input waveform could cause it. Has anyone

encountered this problem and solved it?

No idea about VSDs but electric motors in general cause havoc with RCD's in general usally due to the high in rush currents. Have you noticed any pattern to the occurnaces, ie only happens at start up, during high changes in speed, or under heavry load. Is it a used custom job, or are there others around you can compare it to.