Armature Short-Circuit Brake, Internal Voltage Protection - Siemens SINAMICS S120 Function Manual

Extended Functions

Armature short-circuit brake, internal voltage protection

4.18 Armature short-circuit brake, internal voltage protection
Features
S For permanent magnet synchronous motors
– Controlling an external armature short-circuit configuration
– Internal voltage protection (booksize)
S Configuration via parameter (p1231)
S Status message using a parameter (r1239)
Description
The armature short-circuit and voltage protection functions cannot be simulta-
neously activated.
Armature short-circuit braking is only available for synchronous motors. They are
mainly required when braking in a hazardous situation, if controlled braking using
the drive converter is no longer possible, e.g. when the power fails, EMERGENCY
STOP etc. or if a non-regenerative feedback infeed is used. In this case, the motor
stator windings are short-circuited – either internally or via external braking resis-
tors. This means that an additional resistance is inserted in the motor circuit that
supports reducing the kinetic energy of the motor. In order that the drive remains in
closed-loop control during voltage dips and failures, a buffered 24 V power supply
(UPS) must be used. High-speed permanent-magnet spindle drives for machine
tools are a typical application for armature short-circuit braking.
The functions can be initiated with a "0" signal at binector input p1230. Initially, the
pulses are cancelled and then the armature is short-circuited or the voltage protec-
tion. Using r0046.4, the initiation of these functions via p1230 can be checked.
External armature short-circuit braking
This function controls an external contactor via output terminals that then short-cir-
cuits the motor through resistors. Armature short-circuit braking has the advantage
with respect to a mechanical brake that at the start of braking (at a high speed),
the braking effect is initially high. However, at lower speeds, the braking effect is
significantly decreases – this is the reason that we recommend a combination with
a mechanical brake.
The external armature short-circuit is activated via p1231 = 2 (with contactor feed-
back signal) or p1231 = 3 (without contactor feedback signal). It is initiated when
the pulses are cancelled.
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SINAMICS S120 Function Manual, 03/2006 Edition