82 Standard programposi features
Brake chopper
A brake chopper can be used to handle the energy generated by a decelerating
motor. When the DC voltage rises high enough, the chopper connects the DC circuit
to an external brake resistor. The chopper operates on the pulse width modulation
principle.
The internal brake choppers of ACS880 drives start conducting when the DC link
voltage reaches 1.156 × U
DCmax
. 100% pulse width is reached at approximately 1.2 ×
U
DCmax
, depending on supply voltage range. See table under Voltage control and trip
limits (page 81). (U
DCmax
is the DC voltage corresponding to the maximum of the AC
supply voltage range.)
For information on external brake choppers, refer to their documentation.
Settings
See parameter 01.11 DC voltage (page 105) and parameter group 43 Brake chopper
(page 276).
Safety and protections
Emergency stop
The emergency stop signal is connected to the input selected by parameter 21.05
Emergency stop source. An emergency stop can also be generated through fieldbus
(parameter 06.01 Main control word, bits 0…2).
The mode of the emergency stop is selected by parameter 21.04 Emergency stop
mode. The following modes are available:
• Off1: Stop along the standard deceleration ramp defined for the particular
reference type in use
• Off2: Stop by coasting
• Off3: Stop by the emergency stop ramp defined by parameter 23.23 Emergency
stop time.
With Off1 or Off3 emergency stop modes, the ramp-down of the motor speed can be
supervised by parameters 31.32 Emergency ramp supervision and 31.33 Emergency
ramp supervision delay.
Notes:
• For SIL 3 / PL e-level emergency stop functions, the drive can be fitted with a
TÜV-certified FSO-xx safety options module. The module can then be
incorporated into certified safety systems.
• The installer of the equipment is responsible for installing the emergency stop
devices and all additional devices needed for the emergency stop function to fulfill
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