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Supermoderator
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Discussion Starter #1
I have a chance to buy a very slightly used DeVilbiss compressor. It has a 100 gallon tank and is rated at 140 PSI working pressure. The problem is its 3 phase motor (5HP). I've checked prices for 1 phase motors to do a swap, but they cost $500 and up. The whole rig is costing $200, so a cheaper alternative is needed. I've read about converters that will run 3 phase equipment on 1 phase service. I found a couple in the $100 range, but i don't know if they really work or if they are snake oil. Comments please.
 

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Charter Member
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126 Posts
Joe,

I've been running a 5 horse, 3 phase compressor on single phase 220 AC with a phase converter for about 5 years without any trouble. My converter was made by Phase-A-Matic in Palmdale, CA. You can order these through McMaster-Carr.

Get a good one (high capacity) and your motor will never notice the difference!

Dave Lowen
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FFR4501, Mark II, No donor build
 

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FFCobra Captain
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3,440 Posts
My father's run a compressor on a Phasechanger of similar spec to Dave's Phase-a-matic for years. However, it's seldom cheaper to run a converter if a replacement single phase motor can be found.

A static converter, as sold very cheaply from McMaster Carr as "(A)Light-Load Transformers", should not be used for a compressor. These converters are designed for multiple motor applications. You'll only get 70% performance from the converter (assuming a wye-wound motor, 50% with a delta-wound (but I've never seen a compressor with a delta-wound motor) and the initial load will substantially reduce the lifespan of the converter.

To overcome this with Phase-a-Matic's static converters you can use an idler motor, details here, or a rotary converter. I don't know if McMaster Carr's static converters can be used in this configuration.

An idler motor used as shown above would be illegal in a business environment in England, owing to the possibility of an accidental overload situation, but is safe as long as good working practices are followed.
 

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Supermoderator
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Discussion Starter #4
UK, I think you're right. The least expensive converter is about $500, and I can get a new 1PH motor for $200. This is exactly the opposite of what I thought. Plus, the motor shop said they'd trade the 3PH motor in once they tested it. So maybe I'll end up with a big, fancy compressor for under $300.
 
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