Motor Single Phased
 
Single phasing is a failure mode that indicates a problem in the motor control.  Single phasing is a condition caused by the motor running on 2 phases instead of three.  Although a motor will not start when under a single-phase condition, it could stay running if the condition occurred during operation.   

There are two distinct patterns that occur when a motor has been single phasing and the pattern displayed will depend on the internal connection of the motor:

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If the phases are connected in series there will be two phases burned out and one phase that has no appearance of damage.

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If the phases are connected in parallel there will be one phase burned out and two phases that have no appearance of damage.

 If the cause of single-phasing goes undetected the rewound or replacement motor will continue to fail until the problem is repaired.