ABB ACS880-604LC, Hardware Manual

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Operation principle and hardware
description
Contents of this chapter
This chapter introduces the operation principle and construction of the brake unit.
Product overview
The ACS880-604LC is a liquid-cooled resistor brake unit available in the ACS880 multidrive
modules product range. The design presented in this manual has an NBRW-669C
liquid-cooled brake chopper module with two brake resistors. The chopper module has a
liquid-cooled heat sink which transfers most of the generated heat into the coolant. The air
inside the cubicle is circulated by a fan, and forced through an air-to-liquid heat exchanger.
The two resistors are installed in a separate air-cooled cubicle and share another cooling
fan.
An optional attenuator mounted in the chopper module cubicle suppresses voltage spikes
at chopper input. The attenuator
must be installed if it is possible to disconnect all inverter
units from the DC link with the supply unit on.
Chopper/resistor combinations can be connected in parallel to achieve a higher braking
capacity. However, each chopper module must have its own resistors.
Operation principle
The brake chopper handles the energy generated by a decelerating motor. The chopper
connects the brake resistor to the DC link of the drive whenever the voltage exceeds an
2
Operation principle and hardware description 13