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Old 09-25-17, 11:19 PM   #18
TechShop
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Quote:
Originally Posted by jeff5may View Post
An unloader valve can be installed to overcome that obstacle.

If three phase compressors are used with individual VFDs, there should be no problem starting up against the pressure differential.

The trouble is that most of us are using single phase motors with capacitor start which has very slow start and low rotor torque. My 4 ton unit is single phase.

These days, small 1HP VFDs are cheap and common and they will make 3 phase from standard 240V single phase. Controlling a bank of several of them with an inexpensive surplus PLC is a relatively simple setup.

Multiple compressors would be an interesting project for sure.
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