Generator sizing help

[farmerspark]

Hi all.
I've been out to look at a mates new (to him) air compressor. It's 15kw 3phase star-delta run. He's off grid and currently has a 20kVa Genny running his farm.

This is obviously undersized for starting the compressor, when tried the Genny bogs down and contactors start chattering. He's going to buy another used Genny. He's thinking 30kVa.

Can anyone offer some advice to help me size this correctly?

Thanks

 

[Rockingit]

Unless you've got an already 'warm' set under load, any sudden inductive inrush is going to cause a genny of any size to splutter. If you're looking at getting a second set my personal preference would be to get something like a 30-40 and fit syncing panels to both so that they can be used asynchronously (take a look at DSE stuff). Also means that at busier times (electrically) there's overhead available. You don't have to run both sets at the same time, you can flip between either or both. Also has the benefit that you can take one offline for maintenance but still have power.

 

[farmerspark]

To be honest, the set up is less than ideal, he has the generator that is at most used to run individual pieces of workshop equipment, welder, compressor etc, and to top up his off grid battery storage for his house.
The Genny is only started as and when he needs it. Probably rules out the syncing panels.

 

[brianmoooore]

You may be able to improve things by modifying the compressor so that it dumps the air coming from the compressor for a few seconds, until the generator has recovered from starting the motor.