Rockwell Automation AK DBU - Dynamic Braking Unit 600/690 VAC - Manual (Page 8)

P-4 Overview
The DBU includes the following main components:
The Chopper Transistor is an Isolated Gate Bipolar Transistor
(IGBT). The Chopper Transistor is either ON or OFF. When in the
ON state the Dynamic Brake Resistor connects to the inverter’s DC
bus and dissipates regenerated energy from the load. When in the
OFF state, the Dynamic Brake Resistor is electrically isolated from
the inverter’s DC bus and no energy regeneration occurs. Several
transistor ratings are used in the available DBUs. The most important
rating is the collector current rating of the Chopper Transistor that
contributes in determining the minimum ohmic value used for the
Dynamic Brake Resistor.
Chopper Transistor Voltage Control BUC (PWM type) regulates
the voltage of the DC Bus during regeneration. The average DC bus
voltage is 950V DC for 600V AC input and 1090V DC for 690V AC
input.
DBU Overtemperature Sensor located in the heat-sink for thermal
protection of the DBU.
Power Resistor (customer supplied) or resistor assembly with
Overtemperature Sensor for thermal protection. If the resistor
overheats, this contact disables the connected drive(s).
RC-snubber circuit
Cooling Fan that must be connected to a customer supplied 115V AC
Power Supply. The fan must run if the inverter is energized.
Diagnostic card BUB
The breaking unit includes the BUB diagnostic card with the two
indicating LEDs DC Power on and Brake on.
Description and Block Diagram