Operation principle and hardwaredescriptionContents of this chapterThis chapter introduces the operation principle and construction of the brake unit.Product overviewThe ACS880-604LC is a liquid-cooled resistor brake unit available in the ACS880 multidrivemodules product range. The design presented in this manual has an NBRW-669Cliquid-cooled brake chopper module with two brake resistors. The chopper module has aliquid-cooled heat sink which transfers most of the generated heat into the coolant. The airinside 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 coolingfan.An optional attenuator mounted in the chopper module cubicle suppresses voltage spikesat chopper input. The attenuator must be installed if it is possible to disconnect all inverterunits from the DC link with the supply unit on.Chopper/resistor combinations can be connected in parallel to achieve a higher brakingcapacity. However, each chopper module must have its own resistors.Operation principleThe brake chopper handles the energy generated by a decelerating motor. The chopperconnects the brake resistor to the DC link of the drive whenever the voltage exceeds an2Operation principle and hardware description 13
