So, I've got the opportunity to buy a compressor from my employer very cheaply (we're moving buildings and it's basically going to go in the bin / broken into spares if I don't want it). Obviously I'd love a 15Kw screw compressor (it's a nice one and has had little use). But, I don't have 3-phase.....I've read a little bit about rotary phase converters etc. These seem expensive, especially at the size I would need. I've also read that some 3-phase motors can be re-wired to work on single phase at lower outputs. Attached is a photo of the nameplate for the motor. It does appear that you can wire in both star and delta. But with such a big compressor is it even possible to run on 230V? I understand that it'dd suck a good deal of power on startup so maybe that's where it'll come unstuck? I'm begining to think it's more hassle than its worth.......

Appreciate any insight from people who know what they're talking about!



Motor plate

Single phase to 3 phase inverter. We use them a lot at work, and are fairly straight forward to wire up. Siemens and Mitsubishi do some good ones that you might be able to find relatively cheap?

Can you use an inverter on a 3-phase compressor? I'd heard/read/got from a bloke down the pub that compressors are fairly brutal on start-up, and might be too much for an inverter.

More hassle than its worth. Better off selling it to find a purpose built single phase compressor IMO.

I wasn't far wrong: Phase Converter Info

Basically, static converters (the cheaper ones) can't drive a compressor as the initial load is too high, and too different from the running load. This means that the converter can't be matched to the compressor. A digital converter can do the job, but they ain't cheap.

Hi,

Looking at the motor plate, I am not sure it is a dual voltage motor, as it only states a 3 phase voltage. I understand you need a dual voltage motor to run it off a 3ph to 1ph inverter drive.

Ian

I have three phase in my new workshop if you fancy donating it?

Chris

28amps @ 415v

It's a non-starter in more than 1 way I am afraid.

Grab it, eBay it get something a little smaller.

Change the motor to a single phase 240v one. Did that with my lathe, got the motor from machine mart.

Sounds like it's a big compressor - it'll have to be a bl**dy big single-phase motor, and even then it may struggle.

A 3-phase motor is really good at starting against a load without overheating, and will tolerate repeated starts (as you'd get with a compressor with an automatic pressure switch). Single phase motors have a starting winding and don't like to start against a heavy load as this would prevent the motor getting up to speed quickly; the starting winding will be in circuit far longer than it ought to be and it will overheat. Repeated starts will also cause the motor to overheat as the starting winding doesn't get a chance to cool down.

A lathe is an easy load compared to a compressor as it can be wound up very quickly - a compressor is on full load as soon as power is connected.

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Originally posted by coozer
Change the motor to a single phase 240v one. Did that with my lathe, got the motor from machine mart.

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