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Motor to 3phase connection compatability

LionHeart

Oct 4, 2015
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I have a 3 phase motor that draws 6amp on 240V

In my panel box the only free breaker is a 50amp. Am I good to go connecting the 6A motor to the 50A breaker? Theoretically, the motor will only draw as many amps as it needs, right?

Even if I were to replace the breaker with a smaller one, the smallest 3phase breaker is 15A, which is still nearly 3x the 6A.

If this is a no-no, can I get away with running the motor on the 50A breaker until I order a 15A and it arrives?

I also currently have the motor connected via 8 AWG wire and 50A m/f connectors.

I did hook the motor up and when turned on it only hums without spinning, so I don't know what that's about.
 
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Minder

Apr 24, 2015
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Is this wired to a 3ph supply or a domestic 240v system?
M.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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I did hook the motor up and when turned on it only hums without spinning, so I don't know what that's about.
You are probably trying to run a three-phase motor from 220 VAC single-phase house wiring. There is no way this will work and no way to make it work.

You will need to buy a single-phase to three-phase converter rated for the horsepower of your motor. These come in two varieties: solid state and rotary converters. The rotary converter is a single phase motor driving a three-phase alternator and is possibly less expensive, depending on your power requirements.
 

Tha fios agaibh

Aug 11, 2014
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...Or, a frequency drive.
Or, change motor to single phase. (Might be more expensive)
 

LionHeart

Oct 4, 2015
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Got the motor running - the issue was a wire connection in one of the plug connectors wasn't good. Once all the connections were solid the motor started fine.

I am running off of a 240V 3 phase panel.
 

Y2KEDDIE

Sep 23, 2012
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#8 wire is good for 40A, per phase. The Breaker in your panel is supposed to be sized to protect your wire to the motor, not the motor. #6 wire should be used with a 50A breaker. The motor should be protected with a motor starter appropriately sized for the motor.
 

Minder

Apr 24, 2015
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. These come in two varieties: solid state and rotary converters. The rotary converter is a single phase motor driving a three-phase alternator and
The RPC uses a standard 3phase motor, it is ran directly off of 240v 1ph with a phase shift capacitors to the 3rd phase.
I have had one in my shop for about 15yrs off of the Fitch Williams well known design.
M.
 

Tha fios agaibh

Aug 11, 2014
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The amperage for sizing motor protection and the motor wire should be selected from the tables in the NEC book (if your in USA) and overload protection based on fla on nameplate of motor.

In most cases a fuse protecting the motor is sized 175% of the amperage listed in table 430.250, and thermal overload heaters (below motor starter) are sized 115% of the fla stated on the motor name plate.

For motor use, a #8 Copper wire is rated 50a provided terminations and wire are rated for 75 Celsius.
 

Tha fios agaibh

Aug 11, 2014
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If your motor full load current is only 6amps, you can use 14 awg wire.

Motor leads should be sized at least 125% of the flc. #14 is good for 20amps at 75C.

John
 
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