Insulation Bearings for The Motor

Time：2021.03.04  Source：Roller Bearings Suppliers

Overview of insulated bearing

Many maintenance masters will know that the motor should rotate with insulating bearings at the non-driving end, because when the insulating bearings are not used after the motor starts to rotate at a little speed, the shaft voltage, and shaft current will be generated, and the bearing current will make the bearing produce high temperature, which will lead to serious damage to the bearing. A lot of people don't understand this, so everyone will ask "why the motor non-driving end will use insulated bearings?"

First of all, we will understand what is the insulated bearing. The so-called insulated bearing refers to the general name of the insulation performance of the bearing itself that can block the flow of current. Electrically insulated bearing adopts a special spraying process, and the outer surface of the bearing is coated with high-quality film. The film and the substrate have strong binding force and good insulation performance, which can avoid the electric corrosion effect of the induction current on the bearing, prevent the damage caused by the current on the grease, rolling body and raceway, and improve the service life of the bearing. Need WSBC 21316 E, click here to learn more.

Reasons for the use of insulated bearings in the motor

First of all, for safety, at high frequency, the rotor-induced current will be large to prevent the motor shaft current.

If you do not use the insulated bearing, the current will flow through the bearing to form a circulation, and the bearing is prone to heat or electric spray and therefore is damaged.

The frequency conversion speed regulation system in the high-frequency shaft current on the bearing of the most significant characteristics of the electrical corrosion is in the motor bearing inner and outer rings, the ball produced on the rubbing board type of dense groove stripes. So one end of the motor must be electrically insulated bearing.

Consequences of motor inapplicable insulated bearings

1. Axial current will be generated

When the motor is running, the potential difference between the two ends of the shaft or between the shaft and the bearing is called the shaft voltage. If the two ends of the shaft form a circuit through the motor frame, the shaft voltage forms the shaft current. Shaft current is the shaft voltage through the motor shaft, bearing, stator frame or auxiliary device from a closed-loop generated.

2.The shaft current in normal conditions and the shaft voltage is high

Under normal circumstances, the shaft voltage of the motor is low, and the lubricating oil film in the bearing can play the role of insulation, and will not produce shaft current.

However, when the shaft voltage is high or the oil film is not formed stably at the moment when the motor starts, the shaft voltage will cause the discharge breakdown of the lubricating oil film to form a circuit and produce the shaft current. The high temperature produced by the energy release of the shaft current partial discharge can melt many tiny areas on the inner ring, outer ring, or ball of the bearing, and form grooves, resulting in noise and vibration. If the treatment cannot be found in time, the bearing will fail and bring a great impact on the production. Click here to learn more about WSBC 22210 E.

The advantages of using insulated bearings

Electrically insulated bearings can fundamentally eliminate electrical corrosion by integrating insulating properties into bearings, thus improving reliability and increasing machine uptime.

Electrically insulated bearings usually have an outer diameter surface and the end surface of the outer ring with alumina coating. Insulated bearings with inner holes and end faces of coated inner rings. Because the coated surface area of the inner ring is smaller than that of the outer ring, these bearings provide enhanced protection against high-frequency currents.

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