How to eliminate the ground fault of the stator winding of the variable frequency speed regulating motor
1. Winding ground fault. In three-phase windings, there is one or more insulation damages that cause the iron core and the base in the winding to collide with each other and cause the current to communicate with the base. Such a fault is called a winding ground fault.2. Failure performance. When the winding is grounded, if the shell of the variable frequency speed control motor is not connected to the neutral line or the protective grounding of the shell is not good, the machine base will be charged. Test with an electric pen, and you can see the electric pen glow. If you immediately touch the base with your back of your hand, you will be shocked by electric shock and your arms will be numb. It may also cause abnormal sounds, vibrations and overheating during the operation of the variable frequency speed control motor.
3. The effect of winding grounding. After the grounding fault occurs in the winding, if the inverter's motor housing is not properly grounded, the frame will be charged. Although the variable frequency speed regulating motor can still run, when the human body touches the base, the current will enter the human body and form a loop with the earth, which is dangerous to human life. When there is a ground in one phase winding, the ground point forms a loop with the machine base, which reduces the number of coil turns of the phase winding, thereby increasing the phase current, resulting in unbalanced three-phase current. When two of the windings of one phase are grounded at the same time, the two grounded places of the winding are short-circuited by the core and the base. The more turns of a shorted coil, the greater the increase in phase current. If two places of the two-phase winding are grounded at the same time, it will cause a short circuit between phases, burn the coil, and even make the variable frequency speed regulating motor unable to start running.