Phase Loss
Cause:
This is usually caused by a power phase loss (one phase is not powered or the power supply voltage is insufficient), or by a contactor not closing in the circuit, a disconnected wire connection, looseness, or oxidation of the contact.
Characteristics:
One or two phases (4 phases) in the winding are completely black, and the coils are damaged symmetrically and in a regular pattern.
This is a phase loss.
Cause:
This is usually caused by the motor running at excessive current for a long time, overheating, frequent starting or braking, or incorrect wiring (delta connection instead of star connection).
Characteristics:
The winding is completely black, and the end tie is discolored and brittle, or even broken.
3 Turns
Cause:
Enameled wire cracking during the motor manufacturing process.
Characteristics:
Partially burned winding. Usually, if the motor cavity is clean, there is only one burn point.
4 Phases
Cause:
The interphase paper is not properly installed, or the interphase paper (sleeving) is damaged.
Characteristics:
The motor has burned between two adjacent phases.
5. Ground Strike
Cause:
Insufficient creeping clearance between the coil and the end cap base.
Characteristics:
Blackened marks are visible on both the coil and the end cap, or between the end caps.