What kind of check insulation bearing insulation situation

1. Check the purpose and scope in order to ensure insulation performance, need to measure insulation condition of insulation bearing, including insulation resistance, bearing shaft voltage and shaft current. The purpose of the determination of the motor shaft voltage is to know the size of the motor shaft current. Determine the purpose of the motor shaft current is obtained directly through the motor bearing current value. Because of shaft current damage occurs mainly in the frame number is 280 and above of variable frequency power supply of motor and common in large and medium-sized high-voltage motors. So this inspection of these types of motor only commonly found in trial production or to individual by using for the first time a serious impact on the bearing axis current of motor in the improvement design. 2. Insulation bearing the measurement of insulation resistance measurement, can separate the bearing, but it is better to will take place after bearing installed on the shaft. General use 250 v specifications of the insulation resistance meter. Connect the E end of the instrument and rotor; The insulation of the bearing parts, Such as the outer ring) Cover with aluminum foil, aluminum foil fixed with bare copper wire bundle, then connected to the instrument L end; Or install the insulation bearing housings or motor bearing chamber, the bearing or the motor end cover and install the insulation bearing rotor without electricity access conditions, measurement of the insulation resistance between shaft and bearing seat or the motor end cover. Operation and measurement of motor and winding insulation resistance is exactly the same. 3. Shaft voltage testing method should be inspection before bearing seat and metal gasket, metal gasket and insulation resistance between metal base, to ensure that the motor insulation is good. Between motor bearings and casing with insulating ring ( Pad man dry insulation between bearing and shaft) Or use the insulation bearing, ensure good motor bearing insulation ( At the same time should check bearing respectively with metal gasket, metal gasket and insulation resistance between metal base) 。 Should be determined for the first time, the participants motor no-load running under the rated voltage, rated frequency, high internal resistance with a range of 100 mv millivoltmeter ( Such as transistors or thermoelectric potential millivoltmeter, digital millivolt table, etc. ) Measure shaft voltage U1, then use wires to the shaft end and short answer, another bearing measurement of the earth's axis voltage U2, measurement will lead to dismantle. Test point surface contact with the millivoltmeter fuses should be good. The second measurement, participants motor under the rated current, rated frequency load rated load operation, measurement of bearing voltage U3. Measuring location diagram as shown in the figure below. In a variety of large and medium-sized motor will be determined in the national or industrial standards shaft voltage in the test, and test method are given, but did not specify the eligibility criteria. Therefore, when this test is required, make internal control standard should be according to specific situation. 4. Bearing current measurement method to use the electric motors of the rolling bearing, shaft current measured referring to the following figure. In the motor shaft and the bearing between the casing and equipped with insulated ring ( Cushion between bearing and shaft into the dry insulating film) Or use the insulation bearing, ensure the motor bearings in good insulation. Ammeter in series to contact with both sides bearing insulation layer on the metal parts of no-load running under the rated voltage, rated frequency, measurement of current value, namely the shaft current. The use of sliding bearing and rolling bearing motor, such as not according to the above method, can adopt the method of shaft placed on current transformer measurement shaft current.