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Old 04-15-2019, 03:43 PM
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alchemist alchemist is offline
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Default Motor starters

If you have a three phase motor starter with a fuse for each leg; and one fuse blows. Will the motor burn up from running on single phase?
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Old 04-15-2019, 03:57 PM
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Originally Posted by alchemist View Post
If you have a three phase motor starter with a fuse for each leg; and one fuse blows. Will the motor burn up from running on single phase?
If the overloads in the motor starter are properly sized it should trip out before causing damage to the motor. If the motor is only overloaded.

when you blow 1 fuse and the motor continues to run it will be single phasing causing more amp draw than the overloads are rated for on the other lines providing power to the motor, When the overloads trip out, the control voltage to the coil on the motor starter contactor should open up.

A motor starter is usually a contactor with an overload, that makes it a motor starter.

This is the terminology I am familiar with.

Scott
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Old 04-15-2019, 07:29 PM
Norcal Norcal is offline
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It might or might not, but static phase converters work by starting a 3Ø motor then it single phases with a loss of 1/3 of the HP. On critical equipment, phase loss protection is sometimes added.
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Old 04-16-2019, 03:04 AM
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GWIZ GWIZ is offline
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Originally Posted by alchemist View Post
If you have a three phase motor starter with a fuse for each leg; and one fuse blows. Will the motor burn up from running on single phase?
Running true three phase, no converters.
The luck I had, 9 out of 10 motors will fry when they single phase.
Being that most motor starters have heaters they take too long to heat up in order to save a motor.
motor starters are more if the motor is physically overloaded.

As stated they do have open phase protectors or whatever they are called, never got around to trying one.
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