Inverter board

[Philip d1]

Hi there I was wondering mcb keeps tripping, windings are ok not mechanical seized I was wondering would my inverter board trip the breaker if faulty the second I turn isolator at outdoor mcb trips at mains

[marc5180]

On what system? I assume an AC system and not a VSD?

If you mean on an AC system then yes it could do, especially if the noise filter board has also failed.

[Philip d1]

Yes on a/c system it's a 3 phase compressor first I thought short circuit or grounded but resistance on windings are good I had 2.5 ohms across each winding and carried out megger test so then I thought mechanical but it's tripping even before compressor is called for.

[install monkey]

what type of breaker ? b type typically for lights and sockets c an d type for ac units /motors- will take more of an inrush

[marc5180]

You have checked the 3 phase rotary isolator haven't you? There could be a dead short in there, maybe water has got in.
It's worth confirming that first.

[Philip d1]

It's an c rated breaker..I need to call back and go through everything as I don't believe my compressor is causing the fault.is it possible winding insulation it badly damaged making compressor pull more current without giving me a short circuit or ground reading that there about to go.

[marc5180]

If the winding insulation was bad, you would have picked it up on the insulation and resistance test.

Why not disconnect the compressor terminals to rule the compressor out for certain.

[Philip d1]

Il have to do that in the morning first thing and go form there.thanks for the help

[install monkey]

inverter would detect overcurrent before a breaker trips

[Philip d1]

Ended up being inverter board and noise filter blown.i disconnected compressor still tripping