Writer: Eric Bearing Limited
Overcurrent often occurs on wheelset bearings and traction motors (rail vehicles), DC and AC motors (power transmission systems), and generators (wind power). Overcurrent may cause damage to the raceway and rolling elements and the aging of the lubricant, causing premature failure of the motor or generator, resulting in increased maintenance costs and losses caused by shutdowns and shutdowns.
Rolling bearings used in some related equipment such as motors and generators are likely to be affected by the passage of current during use. This will not only damage the rolling elements and raceways in the bearings, but also affect the grease. performance.
In general, it is very difficult to completely eliminate the potential difference inside the bearing, but it can prevent or greatly reduce the current passing through the bearing to prevent electrical corrosion of the bearing. The induced voltage generated along the shaft will generate a current loop through bearing A, bearing housing and bearing B at the same time.
One reason for this type of shaft voltage is due to the uneven distribution of magnetic flux inside the motor, especially in motors with few pole pairs.
In this case, as long as the bearing at one end is insulated, the current loop can be completely cut off, and the bearing at the non-drive end is usually insulated. If a voltage occurs between the shaft and the bearing housing, current will flow through each bearing in the same direction. In this case, the bearings on both ends of the motor should be insulated.
The decisive factor in choosing insulation is the time characteristic of the current. If it is a DC voltage or a low-frequency AC voltage, the insulation effect depends on the pure resistance value of the insulation layer; if it is a high-frequency AC voltage (common in equipment that uses an inverter), it depends on the capacitance reactance value of the insulation layer.
Is it too professional to look at these, but as long as we have products to deal with them, that is electrically insulated bearings. Both the inner ring and the outer ring with ceramic coating bearings are called insulated bearings.
The ceramic coating can prevent electric current from passing, and has the insulating ability. The rolling elements of the hybrid bearing are made of ceramics, and the rolling elements prevent the current from passing through, so they also have insulation capabilities.
FAG insulated bearings are standard bearings with ceramic coating Insutect on the outer ring or inner ring, and have the following characteristics:
Good insulation performance: bearings with ceramic oxide coating have a suffix (J20), this coating is applied to the bearing surface by plasma spraying. The ceramic has no hardness, high abrasion resistance and good thermal conductivity. ERIC BEARING LTD can supply FAG Insulating bearings , professional FAG bearing distributor .
Insulation layer J20AB: The outer ring is coated to prevent the induced corrosion of the bearing caused by the induced voltage along the shaft. Due to the special sealing process, the J20AB coating can still have a good insulation effect even in a humid environment.
Insulation layer J20AA: It is also coated on the outer ring, and the thickness of the coating is twice that of J20AB. Therefore, it can still have a good insulation effect under the shaft current of higher frequency.
Insulation layer J20C: The thickness of the insulation layer of J20AA is the same. Only the inner ring is coated with insulation. Because the coating area is smaller, the effect of preventing high-frequency shaft current is better. Especially suitable for occasions with high-frequency shaft current and outer ring rotation.
Insulation layer J20A and J20B: J20A is suitable for relatively large-sized insulated bearings; J20B is suitable for those occasions requiring general insulation.
FAG coated insulated bearings are interchangeable with standard bearings. The 62 series deep groove ball bearings have coated insulated bearings, and insulated bearings with sealing rings on one or both sides can also be ordered by agreement.
The insulating bearing coating of FAG company adopts plasma spraying process, which can make the oxide coating adhere to the base material very firmly. The base material needs to be roughened in advance. The final coating also needs to go through a sealing process. Product coating type
It should be noted that the surface of the insulating bearing ring that needs to be coated must be cylindrical, and there must be no lubricating oil grooves or oil holes.
The coated insulated bearings produced by FAG Company have excellent performance, and different use environments and requirements are more subdivided. As long as the equipment needs, there is always a product that can meet your needs and block the corrosion of current.