Armature Short-Circuit - Siemens SINAMICS S120 Function Manual

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Armature short-circuit

You set the "Armature short-circuit" function in the parameter p1231[0...n]. You can determine

the current status of the function in r1239.

● Operation with permanent-magnet synchronous motors

Function description

Motor accelerates uncontrollably for pulling loads

For pulling loads, for an armature short circuit, the motor can uncontrollably accelerate if a

mechanical brake is not additionally used. If the motor accelerates uncontrollably this can

result in severe injury or death.

● For pulling loads, only use armature short circuit braking to support a mechanical brake (a

Using the "Armature short-circuit" function, you can brake permanent-magnet synchronous

motors. The stator windings of synchronous motors are then short-circuited. For a rotating

synchronous motor, a current flows that brakes the motor.

The function is preferably used in the following cases:

● Braking without regenerative feedback

● Braking when the power fails

● Operation with a line module that is not capable of energy recovery

● Braking the motor despite loss of orientation (e.g. when there are encoder errors)

You can switch the armature short-circuit internally via the Motor Module or externally using a

contactor circuit with braking resistors.

The advantage of armature short-circuit braking over a mechanical brake is the response time

of the internal armature short-circuit braking with just a few milliseconds. The response time of

a mechanical brake is about 40 ms. For external armature short-circuit braking, the slowness

of the switching contactor results in a response time of over 60 ms.

Drive functions

Function Manual, 06/2019, 6SL3097-5AB00-0BP2

mechanical brake is mandatory).

Basic functions

8.12 Armature short-circuit