ABB ACS880 - Page 439

Def / Type
FbEq 16b / 32b
DescriptionName / Range /
Selection
No.
3Brake chopper starts to conduct at 100% pulse width
whenever
• The DC voltage exceeds the overvoltage fault limit
(a hysteresis applies), and
• The drive is not modulating (for example, during
a coast stop).
The thermal model-based resistor overload protection
is not active.
This setting is intended for situations where
• The braking chopper is not needed for runtime
operation, ie. to dissipate the inertial energy of
the motor,
• The motor is able to store a considerable amount
of magnetic energy in its windings, and
• The motor might, deliberately or inadvertently, be
stopped by coasting.
In such a situation, the motor would potentially
discharge enough magnetic energy towards the drive
to cause damage.
To protect the drive, the brake chopper can be used
with a small resistor dimensioned merely to handle the
magnetic energy (not the inertial energy) of the motor.
Overvoltage peak
protection
On / uint32Selects the source for quick brake chopper on/off
control.
0 = Brake chopper IGBT pulses are cut off
1 = Normal brake chopper IGBT modulation allowed.
This parameter can be used to enable chopper
operation only when the supply is missing from a drive
with a regenerative supply unit.
Brake chopper run
enable
43.7
00.Off
11.On
See Terms and abbreviations (page 169).Other [bit]
0 s / real32Defines the thermal time constant for the brake resistor
thermal model.
Brake resistor
thermal tc
43.8
1 = 1 s / 1 = 1 sBrake resistor thermal time constant, ie. the rated time
to achieve 63% temperature.
0...10000 s
0.00 kW / real32Defines the maximum continuous load of the brake
resistor which will eventually raise the resistor
temperature to the maximum allowed value (=
continuous heat dissipation capacity of the resistor in
kW) but not above it. The value is used in the resistor
overload protection based on the thermal model. See
parameter 43.6 Brake chopper function, and the brake
resistor data sheet.
Brake resistor max
cont power
43.9
1 = 1 kW / 1 = 1 kWMaximum continuous load of the brake resistor.0.00 ... 10000.00 kW
Parameters 439