Armature Short-Circuit Braking, Dc Braking; External Armature Short-Circuit Braking - Siemens SINAMICS S150 NEMA Operating Instructions Manual

9.3.10

Armature short-circuit braking, DC braking

9.3.10.1 General
The "External armature short-circuit" function for permanent-magnet synchronous motors
initiates an external contactor which short-circuits the motor via resistors when the pulses
are canceled. This reduces the kinetic energy of the motor.
The "Internal armature short-circuit braking" function for permanent-magnet synchronous
motors short-circuits a half-bridge in the power unit to control the motor power consumption,
thus braking the motor.
The "DC braking" function for induction motors injects direct current into the motor, thus
braking the motor.
9.3.10.2

External armature short-circuit braking

Description
External armature short-circuit braking is only available for synchronous motors. It is used
preferably when braking in a hazardous situation, if controlled braking via the drive is no
longer possible (for example, in the event of a power failure, an EMERGENCY OFF, etc.) or
if no regenerative infeed is used. In this case, the motor stator windings are short-circuited
via external braking resistors. This means that an additional resistance is inserted in the
motor circuit that supports reducing the kinetic energy of the motor.
The external armature short circuit is activated via p1231 = 1 (with contactor feedback
signal) or p1231 = 2 (without contactor feedback signal). It is initiated when the pulses are
canceled.
This function controls an external contactor via output terminals, which then short-circuits the
motor through resistors when the pulses are canceled.
A prerequisite for the use of the external armature short circuit is the use of a permanent-
magnet synchronous motor (p0300 = 2xx).
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
Enclosed Drives
Operating Instructions, 12/2018, A5E36652151A
WARNING
(a mechanical brake is mandatory).
Functions, monitoring and protective functions
9.3 Drive functions
539