Bearing Temperature Control and Axial Currents in Motor Operations

Heating is an inevitable phenomenon in the operation of bearings. Under normal circumstances, the heat generation and heat dissipation of the bearings will reach a relative balance, meaning that the heat emitted is essentially the same as the heat dissipated. This allows the bearing system to maintain a relatively stable temperature state.

Based on the quality stability of the bearing material itself and the lubricating grease used, the bearing temperature of motor products is controlled with an upper limit of 95℃. This ensures the stability of the bearing system without causing too much impact on the temperature rise of the motor windings.

The main causes of heat generation in the bearing system are lubrication and proper heat dissipation conditions. However, in the actual manufacturing and operation of motors, some inappropriate factors can lead to poor operation of the bearing lubrication system.

When the working clearance of the bearing is too small, or the bearing races are loose due to poor fitting with the shaft or housing, causing the bearing to run out of round; when axial forces cause serious misalignment in the axial fitting relationship of the bearing; or when of the bearing with related components causes the lubricating grease to be thrown out of the bearing cavity, all these adverse situations can lead to heating of the bearings during motor operation. The lubricating grease can degrade and fail due to excessive temperature, causing the motor's bearing system to suffer catastrophic disasters in a short period of time. Therefore, whether in the design, manufacturing, or later maintenance and maintenance stages of the motor, the fitting relationship dimensions between components must be well controlled.

Axial currents are an inevitable quality hazard for large motors, especially high-voltage motors and variable frequency motors. Axial currents are a very serious issue for the motor's bearing system. If necessary measures are not taken, the bearing system may disintegrate within dozens of hours or even a few hours due to axial currents. These types of problems initially manifest as bearing noise and heating, followed by the failure of the lubricating grease due to heat, and within a very short time, the bearing will seize due to being burnt. To address this, high-voltage motors, variable frequency motors, and low-voltage high-power motors will take necessary measures during the design, manufacturing, or use stages. The two common measures are: one is to cut off the circuit with a circuit-breaking measure (such as using insulated bearings, insulated end shields, etc.), and the other is a current bypass measure, that is, using grounding carbon brushes to divert the current and avoid attacking the bearing system.