One of the most feared situations in electromechanical debugging is the burning of the motor. If the electrical circuit or mechanical failure occurs, the motor will burn out if you are not careful when testing the machine. For those who are inexperienced, let alone How anxious, so it is necessary to fully understand the regulations on the number of motor starts and interval time, as well as motor-related knowledge.

Regulations on the number of motor starts and interval time

a. Under normal circumstances, the squirrel-cage motor is allowed to start twice in the cold state, and the interval between each time should not be less than 5 minutes. In the hot state, it is allowed to start once; whether it is cold or hot, the motor starts After the failure, the reason should be found to determine whether to start the next time.

b. In the event of an accident (in order to avoid shutdown, limit the load or cause damage to the main equipment), the number of starts of the motor can be started twice in a row regardless of whether it is hot or cold; for motors below 40kW, the number of starts is not limited.

c. Under normal circumstances, the starting frequency of the DC motor should not be too frequent. During the low oil pressure test, the starting interval should not be less than 10 minutes.

d. In the event of an accident, the number of starts and the time interval of the DC motor are not limited.

e. When the motor (including DC motor) is performing a dynamic balance test, the starting time interval is:

(1).  Motors below 200kW (all 380V motors, 220V DC motors), the time interval is 0.5 hours.

(2).  200-500kW motor, the time interval is 1 hour.

Including: condensate pump, condensate lift pump, front pump, bank water supply pump, furnace circulation pump, #3 belt conveyor, #6 belt conveyor.

(3).  For motors above 500kW, the time interval is 2 hours.

Including: electric pump, coal crusher, coal mill, blower, primary fan, suction fan, circulation pump, heating network circulation pump.

Motor cold and hot state regulations

a. The difference between the core or coil temperature of the motor and the ambient temperature is greater than 3 degrees, which is a hot state; the temperature difference is less than 3 degrees, which is a cold state.

b. If there is no meter monitoring, the standard is whether the motor has been shut down for 4 hours. If it exceeds 4 hours, it is cold, and if it is less than 4 hours, it is hot.

After the motor is overhauled or when the motor is newly put into operation for the first time, the starting time and no-load current of the motor should be recorded.

After the motor starts, if it trips due to reasons such as interlock or protection, the cause should be carefully checked out and dealt with. It is strictly forbidden to start again for unknown reasons.

Motor operation monitoring and maintenance:

When the motor is running, the personnel on duty should carry out regular inspection and maintenance, which includes:

1  Check whether the current and voltage of the motor exceed the allowable value, and whether the change is normal.

2   The sound of each part of the motor is normal without abnormal sound.

3   The temperature of each part of the motor is normal and does not exceed the allowable value.

4   Motor vibration and axial series motion do not exceed the allowable value.

5  The oil level and color of the motor bearings and bearing bushes should be normal, and the oil ring should be well rotated with oil, and no oil leakage or oil throwing should be allowed.

6  The grounding wire of the motor casing is firm, and the shielding and protective cover are intact.

7.   The cable is not overheated, and the connector and insurance are not overheated. The cable sheath should be well grounded.

8   The motor cooling fan protective cover is screwed tightly, and the fan impeller does not touch the outer cover.

9  The peephole glass of the motor is complete, without water droplets, the water supply of the cooler is normal, and the air chamber should be dry and free of water.

10  The motor has no abnormal burnt smell and smoke.

11  All signal indications, instruments, motor control and protection devices related to the motor should be complete and in good condition.

For DC motors, it should be checked that the brushes are in good contact with the slip ring, there is no fire, jumping, jamming and severe wear, the surface of the slip ring is clean and smooth, there is no overheating and wear, the spring tension is normal, and the length of the carbon brush is not less than 5mm.

The bearings of the motor and the external inspection of the motor are the responsibility of the relevant personnel on duty.

The lubricating oil or grease used for the motor bearings should meet the operating temperature requirements of the bearings, and the lubricating substances used should be replaced regularly according to the requirements of use.

To measure the insulation work of the motor, after contacting and obtaining permission, the equipment will be powered off and the measurement will be carried out. For the equipment that fails to measure the insulation, it should be logged in the record book in time, and reported, and exit the operation.

When the motor does not run normally or needs to change its operation mode, it must be contacted with the chief or the superior responsible person for consent.

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Post time: Mar-14-2023