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How to prevent encoders malfunctioning as a result of bearing currents

Kubler 4/16/2018

Preventing Encoders From MalfunctioningDespite their high level of reliability when used in an industrial environment, encoders are not basically immune to all the stresses and strains imposed on them. So, for example, the high precision opto-electronic measuring systems are sensitive to bearing currents.

Particularly at risk are encoders in large drives such as asynchronous motors and AC vector motors, used for example in mixers and agitators, grinders and plastic-film production plant. The bearing currents that occur here can cause lasting damage to the encoders. The current flowing over the housing of the antifriction bearings leads to the gradual destruction of the bearing races in the motor or encoder.

In order to counteract this Kübler has developed an insert that provides galvanic isolation between the encoder shaft and the motor shaft, preventing the current from flowing across the motor- and encoder bearings. To achieve the best results it is recommended that the tether arm be isolated too. To answer this need Kübler has designed isolated torque arms especially for this type of application and so, for a relatively small investment, the servicing intervals and life of the motor can now be considerably extended.