Electrically insulated bearings use a special spraying process, which is sprayed with a high-quality coating on the surface of the bearing. The coating has a strong separation force from the substrate and good insulation performance. It can prevent the electric corrosion of the induced current on the bearing and avoid the smooth grease and rolling elements. 1. The damage caused by the raceway improves the service life of bearings. The process has been improved from time to time. In insulated bearings, a 100 μm thick coating is applied to the outer ring or outer ring, which can accept a voltage of 1000 VDC.
The special spraying process can form a layer with an average thickness and strong adhesion, and then after further treatment, it can be protected from moisture and humidity. In order to ensure the insulation performance, the insulation condition of the insulated bearing needs to be stopped. Measurement, which includes bearing insulation resistance, shaft voltage and shaft current. The purpose of measuring the motor shaft voltage is to understand the magnitude of the motor shaft current.
The purpose of measuring the motor shaft current is to directly obtain the value of the current flowing through the motor bearing. The damage to the shaft current mainly occurs in motors powered by variable frequency power supplies of frame size 280 and above and ordinary large and medium-sized high-voltage motors. Therefore, this inspection usually only stops for these types of motors during the initial trial production or for individual motors that have found that the shaft current has a serious impact on the bearings due to the use of the design.
When measuring the insulation resistance of insulated bearings, the bearing can be stopped separately, but it is better to stop the bearing after it is installed on the rotating shaft. The insulation resistance meter with 250V specification is generally selected. Connect the E end of the instrument to the rotating shaft; after the insulation part of the bearing (such as the outer ring) is covered with aluminum foil, bind the aluminum foil with bare copper wire and fix it to the L end of the instrument; or install the insulated bearing in the bearing seat or motor end Cover the bearing chamber.
In the state where there is no electrical path between the bearing housing or the motor end cover and the rotating shaft of the insulated bearing of the device, measure the insulation resistance between the rotating shaft and the bearing housing or the motor end cover. The measurement operation is the same as the measurement of the insulation resistance of the motor and the winding to the ground. The method of measuring the bearing current. For the motor using a rolling bearing, the shaft current is stopped as shown in the figure below.