Current imbalence in a 3phase p.t.o driven generator.

Collie & Duthie · Feb 8, 2012

A number of 3 phase induction motors and a single phase motor are fed via a p.t.o driven generator. There is a small current imbalence between the phase feeding the single phase motor and the other 2 but this i think is acceptable. How much of a current imbalenbce in amps (A) would be deemed dangerous to the generator either over heating or in worsed case scenario blowing a winding if all circuit protection fails. Also how long would it take to cause such damage if the generator is in constant use?

malcolmsanford · Feb 8, 2012

What are your generator tolerances? Do you have a programmable Generator protection relay or some sort of command control system on the generator itself?

Every generator manufacturer will have their own tolerances built into their generator and current unbalance will be one of them. You will need first off to contact the generator manufacturer and get their tech specs.

The negative-sequence component (I2) of stator current is directly proportional to the load unbalance and sets up a counter acting flux field in the machine. This in turn cause heating in the rotor iron and then severe damage

The capability of a generator to withstand heat caused by unbalance currents is typically experessed in terms of an constant, and is supplied by the manufacturer of the machine.

Engineer54 · Feb 8, 2012

Would be nice to know what sort of imbalance your talking about seeing on your generator!!

Much more info is needed, like what is the KVA rating of the Genny, what are the loadings of these 3 ph and 1ph motors. What sort of duty cycles your working too, or are these motors constantly running??

By the way, what does p.t.o mean?? Is it ''Part Time Operation''?? If so, do you mean this Genny is a stand-by power source??