Analysis of motor

1. Phenomenon:

In the use of the motor, if the motor is not grounded, it will be found that the motor has "leakage". When measured with an electric pen, the motor shell is charged. When measured with a voltmeter, sometimes the voltage above 100V will be measured, so that people mistakenly think that the motor has "leakage".


2. Analysis:

Since there are equivalent capacitors between the motor winding coil and the motor metal outer shell, when the motor is powered with power frequency AC, the AC can flow to the shell through the capacitor, resulting in the charging of the shell. This current is temporarily called leakage current. Because the equivalent capacitance C has a small capacity of only a few thousand pics, it has a large capacitive reactance for 50Hz AC, so the leakage current L is very small, Even if people touch it, they only feel numb electricity and won't hurt people.


3. Solution:

The PE grounding terminal of the motor is grounded so that the leakage current L is released to the earth through the grounding wire, so there is no feeling of "leakage". At the same time, according to the safety regulations and standards, in order to ensure safety and prevent electric injury to the motor shell caused by motor burning or insulation failure, the PE grounding terminal of the motor must be grounded.