- Difference of insulation damage and fault analysis
1、coil Short circuit
（11）most of the coil is good, partial burn out ,as the picture shown
（2）Cause analysis
①the insulation layer of wire is damaged and When the motor is used, the coil voltage exceeds the breakdown voltage, then the insulation value is completely destroyed at this time.
—– How to Judge, as long as the motor can run normally sometimes,You can eliminate this point of failure,it always happened at new motor , and the running motors rarely appear.
②During motor operation , have solid object enters or rotor parts fall off, causing coil broken. The insulation of the coil is damaged then have short circuit fault.
—— How to Judge, the motor has been running for a long time, the current and voltage are very stable, but fault occurs immediately. Generally, the motor will appear after being put into operation for a long time.
③ The motor has been running many times normally, but it cannot be started suddenly with a trip fault occurs.
—- How to Judge: the new motor has been started without problems, after multiple starts or frequent starts, the failure occurs. It usually appears when new motor ,This is caused by frequent start-up and the motor is in an over-current state, which is caused by various factors;
- coil burns out due to phase loss
（1）the motor coil shows regular local burnout；
as the picture shows
①power supply phase loss
②The break switch is out of phase
③Contactor missing phase
④Motor wiring is out of phase
（2）The basis is to check the line, to find the fault point and eliminate it! At the same time adjust protection value of the thermal protection, The whole current value of the thermal protection relay is 0.9-1.1 times of the rated current value;
3、The motor overload cause coil is burnt out
（1）Appearance—-The motor coils are all burnt out all ；
as the picture shows:
（2）Cause Analysis
①New motor trips during operation
—– The new motor trips after running for a period of time, the surface temperature of motor is not very high, but have a pungent odor overflowing of the motor junction box;
This usually occurs when the pump head is too higher than actual use head , the large overload current cause the insulation coil was burnt out when the thermal protection operation was too late ,this situation is occur during the commissioning of the new pump!
②The adjust operation of the motor is good, and a trip occurs after a period of use.
—— how to judge, the motor has been running for a long time,under current is too large to cause thermal protection work,. With the accumulation of time, the motor insulation burns out when it reaches a certain temperature.This is cased when the pump head is more higher than the actual use head
③The try operation of motor is good, after frequent start and stop, the trip happened after a period of time.
—— How to Judge, the motor often starts and stops, the current is too large, but not enough to cause thermal protection action, with the accumulation of time and temperature the motor insulation burns out.
This is generally caused by a bad environment or a bad setting causes the motor start frequently during operation; it is mostly used temporarily and is controlled by an electrical contact pressure gauge; such as fire pump, stabilized pressure pump, or temporary water pump on the construction site;
④The debugging and operation of the motor is good. motor burns out after one and a half years
—— How to Judge, it appears when the bearing is damaged or the motor is blocked, or when the pump operating conditions have changed; the thermal protection setting is too large or aging does not work, this is the most common!
The motor is affected with moisture, insulation value is destroyed, and the motor trip after being energized.
（1） ——how to judge, the environment of the motor is not good, the motor is damp; for example, soaked in water or rain, etc .;
When have this situation, use a multimeter to check the motor insulation before powering on. In principle, the insulation resistance value is not less than 5 megohms, and the actual experience value is more than 1 megohms.
Post time: May-22-2020