ABB ACS880-34, Hardware Manual

Page: 229 / 256

Resistor braking 229
20
Resistor braking
Contents of this chapter
This chapter describes how to select, protect and wire brake choppers and resistors. The
chapter also contains the technical data.
Operation principle and hardware description
Brake choppers and resistors are available as add-on kits for the drive modules.
The brake chopper handles the energy generated by a decelerating motor. The chopper
connects the brake resistor to the intermediate DC circuit whenever the voltage in the
circuit exceeds the limit defined by the control program. Energy consumption by the
resistor losses lowers the voltage until the resistor can be disconnected.
Planning the braking system

Selecting the default brake circuit components
1. Calculate the maximum power generated by the motor during braking ( P
max
).
2. Select a suitable drive, brake chopper and brake resistor combination for the
application, see section Technical data on page 232 . The braking power of the
chopper and drive combination must be greater than or equal to the maximum power
generated by the motor during the braking (
P
br,max
> P
max
).
3. Check the resistor selection. The energy generated by the motor during a 600-second
period must not exceed the resistor heat dissipation capacity E
R
.
Note : If the E
R
value is not sufficient, you can use a four-resistor assembly in which
two standard resistors are connected in parallel, two in series. The E
R
value of the
four-resistor assembly is four times the value specified for the standard resistor.