In the production site, due to factors such as motor selection and improper storage, maintenance, and environmental factors, moisture can enter the motor to form condensation or the motor directly enters the water, resulting in a decrease in the insulation resistance of the motor, which affects the normal use and operation safety of the motor. In this paper, Dalan Motor's small series mainly analyzes the method of drying the squirrel-cage motor in the field under different conditions.
Small capacity three-phase asynchronous motor damp
Drying method: The small-capacity asynchronous motor is easy to disassemble and disassemble. It can be dried or disassembled in the inspection room according to the on-site environment. Generally, the following two methods can be used to dry the motor.
Generally, the small low-voltage asynchronous motor is suitable for external heating and drying of the motor. The operation is relatively simple; the principle is to use the external heat source to radiate, convection and conduct the drying method when drying; generally divided into two methods:
Drying with a light bulb (or infrared bulb), oven, and drying with a hot air blower;
Do not use the bulb or iodine-tungsten lamp to dry too close to the coil to prevent the coil from being blown. Safety luminaires must be used. The temperature should not exceed 100 °C when using the oven.
Large and medium-sized three-phase asynchronous motor damp
There are several drying methods:
First: current drying method
The basic principle of the current drying method is to pass a low-voltage current to the stator winding of the motor, the rotor is blocked, and the motor is dried by the temperature generated by the loss of the motor itself. When the dryer is dry, the stator and the rotor are simultaneously heated, and the drying speed is fast, generally used for capacity comparison. Large high and low voltage motors;
Note: Calculate the maximum current distributed by each phase winding of the stall current, and should not exceed 50%~60% of the original rated current. You can select the voltage level to dry.
Second: motor iron loss drying method
The basic principle of the iron loss drying method is to wind the excitation coil on the stator winding core of the motor, and to input alternating current, so that the stator core generates magnetic flux, and the temperature rise caused by the eddy current loss of the iron core is used to dry the motor.
Other notes:
1 For the motor extracted from the rotor, heat and dry should be carried out in clean air. Clean all parts of the motor before drying.
2 When the motor is dry, the winding temperature of the motor must be lower than the temperature required by its specified insulation level (to ensure safety, below 10 °C below its specified temperature), generally the winding temperature is controlled at 70 °C ~ 80 °C.
3 Motors with excessively wet windings cannot use DC current drying method, and DC has electrolysis.
4 When using current and iron loss method, the motor casing must have a good grounding wire to prevent electric shock. When using a bulb or iodine-tungsten lamp, etc., care should be taken to prevent electric shock.
5 closed type motor, when the rotor is not dry, the junction box or inspection hole of the motor should open a certain gap, and the small low-voltage motor can also open the gap of the motor end cover to facilitate the moisture emission in the motor.
6 During the drying process, the temperature and insulation resistance of each part of the winding are measured periodically and recorded. The initial stage of drying is recorded every 15 to 30 minutes. After 1 to 2 hours, the temperature of the motor must be recorded periodically to prevent damage caused by overheating of the motor.
In fact, there are many specific methods for drying the motor after damp. In the production site, the motor should be dried according to the specific conditions. However, no matter which method is used to dry the motor, the motor temperature must not exceed its allowable value. New damage to the motor insulation, attention to equipment and personal safety during drying; the production site often requires the motor to be put into operation and safe operation in a timely manner. The southern environment is rainy and humid, so as to ensure that the motor does not suffer from moisture and water. For operation or safe operation, specific motor moisture-proof measures should be formulated and attention should be paid to the selection of the motor in a humid environment.
----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant
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