Daily maintenance of slip ring crane duty motors-1
For the maintenance of the slip ring crane duty motors, in order to correct the motor fault correctly and in time to ensure the normal operation of the motor, it is necessary to master the temperature rise, voltage, current, load condition, heat dissipation condition, flexibility of the rotor rotation, and the flexibility of the crane motor. No sound, winding insulation, insulation of lead wires and terminals, and flexibility of the mechanism, etc., to find the fault location correctly and timely.
The slip ring crane duty motor power supply voltage should generally not be higher or lower than 5% of the rated value, the minimum is not less than 15%, and the voltage difference between any two phases does not exceed 5% of the average value of the three phases.
The gap between the stator and rotor of the slip ring crane duty motor is 0.25~2mm. The gap is large, the power factor is low, the gap is small, and the power factor is high, but the assembly is difficult and unsafe. The maximum speed of the bridge crane motor and gantry crane motor must not exceed 2.5 times its synchronous speed.
After the rolling bearing of the three phase electric motor is operated for 1000~1500h, the oil should be added once; after 2500~3000h, the oil should be changed. When the oil is changed, the bearing must be cleaned before adding new oil.
The frame and end cover of the slip ring crane duty motor are not allowed to have cracks. Otherwise, mechanical deformation will occur, resulting in uneven air gap between the stator and the rotor, causing the motor to vibrate. In severe cases, the stator and the rotor will collide and the three phase electric motor will be damaged.Before the new or overhauled crane duty motor is used, in addition to the general visual inspection and the flexibility of the test rotor, the insulation must also be checked with a shaker. The winding insulation resistance of the stator and rotor should be above 2 MΩ, and the minimum rotor should be no less than 0.8 MΩ, otherwise it should be dried. The method is to put the whole motor into the drying box or pass the short-circuit current of low voltage, and the latter is to connect the tail end of each desired winding and the first end to the power supply with the rated voltage of 20%. The current flowing through the motor at this time (ie, the current in the gambling state) should be less than its rated value. Cover the canvas (with vent holes on both the upper and lower sides), and keep the temperature of the slip ring crane duty motor at 40~50 °C in the beginning of 2~3h. After 3 hours, the motor surface temperature was 50~70 °C. The drying time varies according to the insulation performance of the three-phase motor, which is 12 to 20 hours. In this thermal state, the stator insulation resistance is 1 MΩ, and the rotor resistance is 0.5 MΩ. The insulation resistance will increase by 2 to 3 times after cooling.