3 Phase motor running on generator

[mrbarty]

Is there an easy way to determine what size generator is needed to run a 3 phase compressor?

The motor on the compressor is 4 Kw 3 phase. I'm unsure how generators handle the inrush current from the motor starting?

Any help/guidance appreciated, cheers.

[mrbarty]

I'm no generator expert, but you would need to know what the power factor of the motor is, and the efficiency, so you can do the maths to work out the KVA size and then you will have an idea of the size generator required - Generators are speced in KVA

[pluto]

The starting current of the motor is one of the critical factors you have to consider. Remember DOL starter current is up to 8 times the running current when starting.

The use of a motor starter (and a compression lifter in the case of an air compressor) to reduce the starting current is essential, and not a variable speed starter, which requires a considerable level of spare capacity on the generating set.

Also if more than one motor, you have may have to ensure that not more than one motor at the same time is trying to start.

The generator set supplier /generator handbook should be able to assist. But only good brand generating sets/ or alternator manufacturers will come with this detail.

The mechanical output of generating set motor also another that needs to be considered.

It is not an area of knowledge for which there is lots of data is readily available.