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How To Maintain Motors?
Aug 23, 2017

Daily inspection and maintenance of motor

Electric motor by the stator frame, winding and insulation material, rotor, bearing and end cover and so on. Motor failure reasons: power off phase, voltage or frequency wrong, winding short circuit, open circuit, then the bearing dysfunctional, internal and external dirty, cooling is not good, external coating paint is too thick cooling is not good reason and the built-in cooling fan is bad, poor ventilation and mechanical equipment adverse, long-term high load operation, ambient temperature high, and so on. Are maintenance routine inspection personnel is not fine, maintenance problems caused by more than 90% of the damage to the motor, as long as we persist in carefully to see, hear, touch, and do, the vast most failures can prevent and avoid.

 

1 see

Daily inspections at the working current of the motor and the size of the changes, look around, there is no leakage, dripping, whether due to insulation low breakdown winding burn out the motor. Depends on whether the motor periphery has an effect on the ventilation and cooling environment of the object, see the fan end cover, fan blades and motor outside the need to clean, to ensure that the cooling effect of the cooling. No matter who discovered the problem, should be treated in a timely manner.

 

2 listen

Carefully listen to the voice of the motor is abnormal operation. Because of the noise of the machine room, can be with the aid of a screwdriver or a screwdriver, etc., close to the motor at both ends. If you often listen to, not only can find undesirable vibration motor and the driven device, even many of the internal bearing oil can determine to make timely add oil bearing, or replace new bearing the corresponding measures to deal with, to avoid motor bearing is short of oil dry grinding and locked rotor, go round, sweeping the hearth burnt out.

 

Most manufacturers considering large motor disintegration of the difficulty of replacement of bearings, bearing the open, periodically (2000h), oil gas should be paid attention to when using motor brand mark bearing oil (- 35 DEG - + 140C DEG C), and open at the lower end of the oil discharge outlet open or the other side of the bulkhead screws, to old oil squeeze out for (pay attention to add oil quota), prevents the fuel pressure a lot of oil squeezed into the interior of the motor, operation splash to stator and rotor, affected the motor cooling function.

 

3 touch

Temperature of the motor around the back of the hand. In the case of the bearing condition, the temperature of the two ends is lower than that of the middle winding section. If the two ends of the bearing temperature is higher, it is to be combined with the measured bearing sound conditions to check the bearing. If the overall temperature of the motor is high, the load, equipment, ventilation and other conditions of the motor will be checked and the corresponding treatment is carried out. According to the motor used in insulation materials insulation class, you can determine the operation of the motor winding insulation can be used for a long time the temperature limit, or say that electric allowable temperature rise (motor actual temperature minus the ambient temperature). National insulation grade standards vary, but basically divided into: y, a, B, e, F, h, c this several grades, which y allowable temperature rise was the lowest (45 DEG C), and C grade allowable temperature rise at 135 DEG C above). Considering the bearing oil and other materials, with the best control in 85 degrees below the measured temperature by thermometer dear motor.

 

4, measurement

(1) offline: when the motor stops running to regularly (monthly) with insulation meter to measure the insulation resistance of the opposite or alternate, compared with last month's test results, in order to detect the insulation defects. Found that poor drying oven lamp in order to improve the insulation, avoid because of insulation is too low (recommended value > 1 MOhm) breakdown winding burn out the motor. The electric motor is equipped with the electric heating of the electric oven, unless special circumstances, do not turn off the heating switch. In wet weather and winter, special attention should be paid to the motor's waterproof, moisture and drying. In the open and wet places of the electric motor to pay special attention to the water dense; for suspected serious moisture or splashed water motor, using the former more should be carefully checked. If it is found that the soak water of motor, as long as the motor after the disintegration of the out of the rotor, and dry with compressed air, and then roast lamp from the motor stator at both ends in the baking, check the insulation of the motor rose to normal. Some of the motor winding wire only three root, cannot detect a winding insulation, rewinding motor insulation resistance should be not less than 5 megohm.

 

(2) on-line: when the motor is running, it can measure the three-phase operating voltage and current, see whether the balance. Voltage should be basically the same, the current and the average value of the error should not exceed 10%, such as using pincers table measured the phase current difference is too large, it may have inter turn short circuit. Sometimes required to uncouple the no-load current magnitude of the load measurement, general 2 pole about 2800rpm, 1 / 3 ie (rated current), 4 pole about 1600rpm, about 40% of the IE, 6 pole about 900rpm, 55% ie. It will vary with the number and capacity. In addition, the motor of Y and] connection method cannot be wrong, if the wrong Y shaped into a triangle shape, working current will increase, on the contrary, decrease. At the same time, reduce such as motor winding connection error, or the number of turns in the winding, the old motor fixed rotor air gap too large (normal 0.2-1.0mm) will increase the no-load current, these points can help us to judge the quality of the daily operation of motor status.

 

5, do

Not only to check the problems found in time to take remedial measures, but also by the maintenance cycle, (monthly) to the motor for the screw, wiring fastening, dismantling inspection, cleaning, maintenance, etc.. Such as motor end cover four fastening screws are loose, caused by sweep operation bore burn; motor wiring bolts loose virtual connection, cause lack of burn; fan motor leaf shedding withstood the body, resulting in block in turn burned; the poor lubrication of the bearing of the motor, high operating temperature, but did not timely replenishment of lubrication