Indramat modifies drive to tackle bearing currents

Indramat is modifying a recently launched digital motor drive to ensure that it does not result in potentially damaging currents in the bearings of motors that it drives. These currents, associated with high-frequency switching, can lead to sparking in the bearing which can damage the motor irreparably.

Although there is no evidence that Indramat`s new "intelligent" DKR drive has caused bearing current problems, the company is making the modifications as a precaution.

"We know there is a possibility of sparks occurring in a bearing when the interior ring becomes inductively loaded, which can damage it, but we have had no reported problems yet," says Indramat`s managing director, Brian Hedges.

The decision to modify the drives was prompted by a query to Drives and Controls from an Indramat customer, Goss Graphics, which was having problems with a drive on one of its newspaper printing presses. The company suspected that bearing currents were to blame, but a subsequent investigation revealed that the problem arose from a misaligned motor.

Nevertheless, Indramat has decided to modify the DKR drive which is aimed at applications such as printing, converting, packaging, and textile machines. It will also modify Goss` DKR installation.