Traction motors in rail vehicles, DC and AC motors in drive technology as well as generators in wind turbines are often fitted with roller bearing. If it is structurally impossible to prevent the flow of current through the rolling bearings, it is necessary to insulate the rolling bearing.


Avoid passage of current

We manufacture current-insulated rolling bearings that provide reliable protection against the passage of current. An oxide ceramic insulating layer on the connecting surfaces (shell and end face) of the bearing rings effectively prevents the passage of current in the bearing. Expensive conventional insulation methods become superfluous. We offer current insulation up to a breakdown voltage of 3000V (DC) for all standard bearings and for special bearing types.


Current-insulated Bearings symbols

The insulation layer of our bearings can be selected for specific applications. We supply rolling bearings with an insulated outer ring or insulated inner ring.


Close-up of damage from current passage

A first typical sign of current passage is the decomposition of the lubricant. In the course of the damage, microcraters and a matt finish of the raceway, which are not visible to the naked eye, are often mistaken for signs of insufficient lubrication or associated with this. At the end of the damage development, the typical ripple formation only occurs through continuous overrolling.

Special Suffixes


Insulated bearing or bearing parts, suffix followed by a number indicates the affected parts group. A distinction is made between:
5 - Insulated bearing up to 500 V, coated outer ring
10 - Insulated bearing up to 1,000 V, coated outer ring
30 - Insulated bearing up to 3,000 V, coated outer ring
..J - coated inner ring

Interchangeability guaranteed

The main dimensions of the current-insulated bearings are identical to those of standard bearings, making it easy to replace conventional KRW rolling bearings that are too electrically insulated. If it is not possible or sensible to isolate the rolling bearings by design, we also offer bearing insulation discs, which are used, for example, to protect large axial bearings. We also supply current-insulated bearings and insulation discs with diameters of over 1,000 millimetres.


Our hybrid bearings, in which all-ceramic rolling elements are used, offer a further option for current insulation. These have reliable insulation even at high AC voltages and temperatures.

learn more

KRW Products and Services

KRW application ingenieur working on an analysis
Services and Engineering
KRW Stock
Rolling Bearing Stock
KRW Contact