To control a synchronous motor, the position of the rotor must be known at all times. If the encoder fails, this information is no longer available and the motor can no longer be braked in a controlled manner. In applications such as handling axes, injection moulding machines or robots, this can lead to damage to the machine, tools or products.

That is why the Nuremberg-based drive specialist Baumüller has developed the ‘encoderless stop’ function. If a sensor fault is detected, the system switches to sensorless operation within milliseconds. This allows the drive to be braked via a specified ramp or at the current limit and thus with the maximum possible torque. Damage caused by collisions and the resulting long downtimes, repair and replacement costs are thus avoided.

To illustrate this, Baumüller uses an application example from the plastics industry: A handling system on an injection moulding machine transports the finished plastic parts out of the machine. If the mechanics were to coast to a standstill at full speed in the event of a sensor fault, this could result in a collision with the expensive injection mould and cause considerable economic damage. The ‘sensorless stop’ protection function enables the motor to be braked in a controlled manner, thus preventing damage.

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