Maintenance method for winding grounding of Nanyang explosion-proof motor

2023-11-22 11:02:50

The manufacturer of Nanyang explosion-proof motor stated that the grounding of explosion-proof motor winding refers to the grounding caused by insulation damage between the winding and the iron core or the shell.

1. Defect phenomenon

The shell is electrified, the control circuit is out of control, and the winding is short circuited and heated, resulting in the explosion-proof motor being unable to operate normally.

2. What are the reasons for this

Damping of the winding causes a decrease in insulation resistance; Long term overload operation of electric motors; Harmful substance erosion; Metal debris entering the inside of the winding damages the insulation; Insulation damage and iron core collision during rewinding of explosion-proof motor stator winding; Winding top end cap base; Insulation burns caused by friction between stator and rotor; The insulation of the outgoing line is damaged and collides with the casing; Overvoltage (such as lightning strike) causes insulation breakdown.

3. What are the methods for checking

1) Inquiry method. After visual inspection of the insulation at the end of the winding and inside the wire slot, check for any signs of damage or black scorching. If there are any, it is the grounding address.

2) Megohmmeter method. Select different megohmmeters according to different levels to measure the insulation resistance of each group of resistors. If the reading is zero, it indicates that the winding is grounded. However, for motor insulation that is damp or broken down due to accidents, it needs to be judged based on practical experience. Generally, when the meter needle swings at "0", it can be considered to have a certain resistance value.

3) View with a multimeter. The manufacturer of Nanyang explosion-proof motor stated that if the reading value is very small when using a multimeter to check the low resistance range, it is grounded.

4) Current burning method. Using a voltage regulating transformer, after connecting to the power supply, the contact area quickly heats up, and the place where the insulation emits smoke is the contact area. Special attention should be paid to small motors not exceeding twice the rated current for a period of no more than 30 seconds; A large electric motor should have a rated current of 20% -50% or gradually increase the current, and immediately cut off the power when the smoke starts at the connecting address.

5) Lamp test method. Assuming the test light is on, it indicates that the winding is grounded. If a certain point is accompanied by electric sparks or smoke, it is considered a winding grounding defect point. If the light is slightly on, there is a grounding breakdown in the insulation. If the light is not on, but there is also an electric spark when the inspection rod is grounded, it indicates that the winding has not been broken down yet and is only severely affected by moisture. You can also use hardwood to lightly tap on the edge of the outer shell, and when it reaches a certain point, wait for one to turn off and one to turn on, indicating that the current is on or off, then that point is the connection address.

6) Group elimination method. The copper wire and the iron core melted together due to severe burning caused by the address on the inner side of the iron core. The method used is to divide the grounded phase winding into two halves, and so on, ultimately finding the grounding address.

In addition, there are also high-voltage experimental methods, magnetic needle exploration methods, power frequency oscillation methods, etc.

4. How to handle it

(1) Windings that are affected by moisture and form grounding should be dried. When cooled to around 60-70 ℃, insulation paint should be applied before drying.

(2) When the insulation at the end of the explosion-proof motor winding is damaged, insulation treatment should be carried out from scratch at the grounding point, followed by painting and drying.

(3) When the winding connection is inside the slot, the winding should be rewound or some winding components should be replaced.

The above information was compiled and released by the Nanyang explosion-proof motor manufacturer. Thank you for watching.