During the production process of geared motors, it is often found that some geared motors have been left unused for a period of time. When they are put back into operation, the insulation resistance of the geared motor windings is found to be reduced. This is especially true during the rainy season when the air humidity is high, and the insulation value may even drop to zero. At this time, drying treatment should be carried out to bring the insulation resistance and absorption ratio back to the specified values. If the motor is put into operation rashly, the insulation of the geared motor coil may break down, resulting in an accident.
The following are three simplified methods for drying geared motors:
I. External heat source heating method
For damp geared motors, first disassemble and inspect them. Then, use a high-power incandescent light bulb to heat the inside of the motor, or place the motor in a drying oven to dry it. This method is convenient and safe, but only suitable for small geared motors that are easy to disassemble and inspect. For large or medium-sized geared motors or those that are difficult to disassemble and inspect, the workload is relatively large, and the feasibility is reduced. It should be noted that when using this method, the light bulb or heat source should not be too close to the coil to prevent burning it out. You can cover the geared motor casing with a canvas or other material for insulation.
II. Drying method for electric welding machines
a. Drying method for AC welding machines
Before operation, connect the three terminals of the damp geared motor windings in series and ground the casing. This will allow for heating and drying of all three windings. To monitor current changes during the drying process, an ammeter can be connected in series to check if the current reaches the rated current of the geared motor. Drying a geared motor with an AC welding machine eliminates the need for disassembly and inspection, reducing workload. Furthermore, the geared motor heats itself using its own resistance while powered on, ensuring even heating of the coils and resulting in better drying. However, this method is only suitable for the following types of geared motors and cannot be used long-term. Because the current applied to the transformer of an AC welding machine is relatively large during operation, prolonged use may damage the welding machine.
b. Drying method for DC welding machines
The wiring is similar to AC, but the ammeter connected in series should be a DC ammeter. Using a DC welding machine to dry a damp geared motor is convenient and can be used for long-term drying of large and medium-sized geared motors, as well as high-voltage geared motors. This prevents damage to internal components during long-term or high-current operation of the welding machine, allowing for the long-term use of large and medium-sized geared motors. It is important to note that when using either method, all connections must be secure and firmly tightened. The welding machine's leads must be dedicated wires with a cross-sectional area sufficient to carry the output current. Pay attention to the cooling of the welding machine's transformer and ensure the insulation resistance of the geared motor does not fall below 0.1MΩ. Closely monitor the geared motor winding temperature and adjust the voltage and current accordingly.
III. Excitation Coil Drying Method
The excitation coil drying method involves winding an excitation coil on the iron core of the stator coil of a geared motor and passing an alternating current through it to generate magnetic flux in the stator, relying on its iron loss to dry the stator of the geared motor.
