In actual production, the motor is affected by moisture due to improper storage and maintenance, temperature, environment and other factors. Water vapor enters the interior to form condensation beads or the motor directly enters water, causing the motor insulation resistance to malfunction and affecting actual production. Several processing methods are explained in detail below.
Small asynchronous motor
The disassembly of small asynchronous motors is relatively simple and convenient. It can be dried on site or disassembled in a maintenance workshop according to the on-site environment. Generally, small low-voltage asynchronous motors are suitable for external heating and drying methods, and the operation is relatively simple; the principle is to use the radiation, convection, and conduction of external heat sources to dry the motor during drying.
Use infrared bulbs and an oven for drying, or use a hot air blower for drying; use light bulbs or iodine tungsten lamps for drying, and do not get too close to the coil to prevent the coil from being burned. Safety protection lamps must be used. When using the oven, the temperature cannot exceed the temperature of the coil.
Large and medium-sized asynchronous motors
1. Current drying method
The basic principle of the current drying method is to pass low-voltage current into the stator winding of the motor, and use the temperature generated by the loss of the motor itself to dry the motor. During drying, the stator and rotor of the motor generate heat at the same time, and the drying speed is fast. It is generally used for high and low voltage applications with large capacity. motor.
a. Directly connect the low-voltage three-phase AC power to the motor stator winding without pulling out the motor rotor. The motor stator and rotor are dried at the same time, and the drying operation is realized on site.
b. The three-phase windings of the motor are connected in series from end to end (or in series with each other to reduce the current), for motors with 6 terminals; use an AC or DC welding machine or voltage regulator to adjust the current into the stator windings of the motor to dry the motor. It is suitable for drying high and low voltage motors when the on-site power supply capacity is insufficient; when turning on or cutting off the current of the welding machine, the current should be adjusted to zero first to prevent high voltage from damaging the motor insulation; on-site processing does not require pulling out the motor rotor, which is convenient.
c. The three-phase windings of the motor are connected in parallel (for motors with 6 terminals) or two phases are connected in series and then connected in parallel with the other phase (for motors with 3 terminals); use an AC or DC welding machine or voltage regulator to adjust the current flow Motor stator windings to dry the motor.
2. Motor iron loss drying method
The basic principle of the iron loss drying method is to wind an excitation coil on the stator winding iron core of the motor, pass in alternating current, so that the stator core generates magnetic flux, and use the temperature rise generated by the eddy current loss of the iron core to dry the motor.
a. Wrap the excitation coil around the stator core of the motor (through the stator bore), connect the 380V/220V AC power supply, and dry the motor insulation. Scope of application: Large and medium-sized motors, motor rotor core extraction.
b. Wrap the excitation coil around the motor stator shell, connect the power supply through a welding machine and a voltage regulating transformer, and dry the motor insulation. Scope of application: large and medium-sized motors, the motor has been installed on site.
In actual production, there are many specific methods for drying the motor after it gets damp. We should analyze the specific situation and select the appropriate drying method to dry the motor. No matter which method is chosen to dry the motor, it must be noted that the motor temperature cannot exceed its own allowable range, otherwise it will cause new damage to the motor insulation.
When performing drying operations, attention should be paid to equipment and personal safety.
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