In some special application scenarios or specific products, both insulated bearings and ceramic bearings have insulation properties, but their advantages vary due to different application occasions. The specific comparison is as follows:
Insulated bearings are insulated by using a special process on the outer surface of the inner ring or outer ring of the bearing. Its outer surface is covered with a layer of aluminum oxide material with a thickness of about 100 microns, which can withstand a DC voltage of 1000V, and the internal structure of the bearing is no different from that of ordinary bearings.
Aluminum oxide, as an inorganic compound with high hardness, high temperature resistance and strong chemical stability, is widely used in industry, medical treatment, environmental protection and daily life. Its reliable combination with the bearing surface can ensure that the insulated bearing meets the same stiffness requirements as ordinary bearings without affecting the dimensional accuracy of the bearing and its mating parts.
Since the aluminum oxide layer has reliable adhesion and continuity, insulated bearings can effectively block the shaft current loop, so they are widely used in shaft current lightning protection scenarios of motor products. In addition, its consistency with the size of ordinary bearings avoids the problem of design differences of matching parts.
Insulated bearings are divided into internal insulation and external insulation. The insulation layer of the external insulation bearing is located on the outer surface of the outer ring (the matching surface with the bearing chamber), while the insulation layer of the internal insulation bearing is located on the outer surface of the inner ring (the matching surface with the shaft). In contrast, the coating surface area of the internal insulation bearing is smaller, the impedance is greater, and the insulation effect is better.
The special feature of ceramic bearings is that the rolling element material is silicon nitride ceramic. Silicon nitride has excellent characteristics such as high hardness, good self-lubrication, strong wear resistance, high temperature oxidation resistance, and resistance to cold and hot shock (not easy to break under drastic temperature differences).
Ceramic bearings using silicon nitride as the ball material are light in weight and have both electrical insulation and high-speed operation performance. Hybrid ceramic bearings (some parts are made of ceramic materials) are more suitable for high-speed operation and low shaft voltage.
From the perspective of electrical insulation alone, insulated bearings have more advantages, while ceramic bearings show unique applicability under high-speed conditions. Both need to be selected according to specific application requirements.