Understand the predictive maintenance of motor insulation that you don't know
In order to ensure the normal operation of the production line, predictive maintenance is particularly important. The artificial maintenance is to prevent accidental shutdown of the motor and cause huge losses in the production line.
Many companies regularly perform predictive maintenance on insulation. However, although there are periodic insulation tests, the motor will be damaged due to insulation problems. Why? Then let us find out.
Background introduction
The production department of a water company in a city in Fujian is responsible for the safety of water supply production in all cities and counties. The production department will perform regular temperature and insulation performance inspection before the motor is put into operation. However, this routine inspection does not prevent accidental burning of the motor.
The motor installed in 2005 was burned in 2012 for 6 years. The motor installed in 2012 was burned in June 2018, and both motors were burnt out.
Both motors are burned out. Why can't the traditional insulation tester find the insulation problem of the motor winding?
Let's take a look at the voltage at the output and motor terminals of the field inverter.
case study
It can be seen from the measurement results in Figure 5 that the peak-to-peak voltage of the motor is 1640V, and the maximum allowable value of the inverter for the "normal IVICA" insulation class is 1254V. It is this long-term pulse overvoltage that causes the motor to be insulated between turns. The performance is degraded, which eventually leads to a breakdown short circuit and the motor burns out.
For this condition, it is recommended to use a dedicated inverter motor with a pulse insulation rating of at least “medium IVICB”.
in conclusion
The traditional insulation resistance tester can only measure the insulation performance between phase and ground, phase and phase, and the interphase insulation of each phase can not be evaluated, which is why even with the traditional periodic insulation test, There is a motor burnout caused by insulation problems. In this regard, the pulse voltage and overshoot coefficient detection at the motor end is particularly important. With this test, the purpose of predictive maintenance can be achieved, and the huge economic loss caused by the shutdown of the production line can be avoided.
