The reasons for motor burning

The reasons for motor burning can be divided into: load, power supply, motor insulation, default phase

1.Default phase

Reason:Usually due to the lack of phase power.(1 phase unsupplied or insufficient supply voltage).Or the contactor contact point in the line is not closed.The wire connection point disconnects, loosens or contact position oxidizes causes and so on.

Characteristic:One or two phases (level 4) in the windings are all blackened, the coil is damaged symmetrically.

2.Overload

Reason:Generally is long time to run over current, overheat, frequently start or brake, wiring error.

Characteristic:The winding all turns black, the binding at the end becomes discolored and becomes brittle or even broken.

3.Interturn

Reason:Enameled wire breaks from the motor manufacturing process, and water, acid, and other corrosive substances in the system can also cause such failures.

Characteristic:The winding is partially burnt, usually the motor cavity is clean, there is only one blasting point.

4.Electrode two-phase

Reason:The interphase paper is not in place, or the interphase paper (casing) is broken.

Characteristic:The motor burns out between two phases.

5.Strike

Reason: Insufficient distance between coil and end cover seat.

Characteristic:There are burn marks on both sides between the coil and the end cover.

How to prevent the motor from burning？

1. Keep the motor clean

The motor must always keep the air inlet clean during operation.

If dust, oil and water are drawn into the motor, a short circuit medium is formed to damage the insulation of the wire.

Causes interturn short circuit, the current increases, the temperature rises, burns the motor.

2. Work under rated load

Motor overload operation, the main reason is the drag load is too large, voltage too low, or driven machinery stuck.

When the motor moves in a state of overload, the motor speed decreases, the current increases, the temperature increases and the coil overheats.If the motor is overloaded for a long time, it will burn out under the aging failure of insulation at high temperature, which is the main reason for the motor to burn out.

3. Keep the three-phase current steady

For three-phase asynchronous motors, the difference between the average value of any one phase current and that of the other two phase current is not allowed to exceed 10% in order to guarantee the safe and normal operation of the motor.

If the average value of single-phase current and the average value of the other two phase current exceeds the prescribed limit, it indicates that the motor has a fault. The reason must be found out and the fault can be removed before the motor can continue to operate, otherwise the motor will be burnt.

4. Maintain normal temperature

The temperature of the bearing, stator, enclosure and other parts of the motor shall be checked frequently for anomalies, especially for the motor without voltage, current and frequency monitoring facilities and overload protection facilities, and the temperature rise monitoring is especially important.

If the temperature rise near the bearing is found to be too high, it should be stopped immediately to check whether the bearing is damaged or short of oil.If the bearings are damaged, they should be replaced with new bearings before operation. If the bearings are short of oil, grease should be added; otherwise, the bearings will be further damaged, resulting in collapse, which will destroy the motor by sweeping.

5. Observe for vibrations, noise, and odors

If the motor vibrates, it will cause the non-coaxiality of the motor connected with it to increase, which will increase the motor load, increase the current, and increase the temperature and burn the motor.

Therefore, when the motor is running, it is necessary to check regularly whether the anchor bolts, the end cover of the motor and the bearing pressure cover are loose, and whether the connecting device is reliable. If any problem is found, it should be solved in time.

6. Ensure the normal operation of the starting equipment

The main maintenance of the starter is cleaning and fastening.If the contact of contactor is not clean, the contact resistance will be increased, resulting in burning of the contact, causing the lack of phase and burning of the motor.The rust corrosion and dust accumulation of the core of the magnet coil of the contactor will make the coil not close tightly and give out strong noise, increase the coil current, burn the coil and cause faults.

Electrical control equipment should be in dry, ventilated and easy to operate position.Remove dust regularly, tighten all wiring screws, check whether contact of contactor is good and reliable, and whether mechanical parts are sensitive and accurate.Keep the motor in good technical condition, so that the motor can start smoothly without burning.