Allen-Bradley 20A User Manual

8 Rockwell Automation Publication PFLEX-AT001L-EN-P - September 2017
Chapter 1 Understanding How Dynamic Braking Works
Dynamic Brake Components
A Dynamic Brake consists of a Chopper (the chopper transistor and related
control components are built into PowerFlex® drives) and a Dynamic Brake
Resistor.
Figure 1 shows a simplified Dynamic Braking schematic.
Figure 1 - Simplified Dynamic Brake Schematic
Chopper
The Chopper is the Dynamic Braking circuitry that senses rising DC bus voltage
and shunts the excess energy to the Dynamic Brake Resistor. A Chopper contains
three significant power components:
The Chopper Transistor is an Isolated Gate Bipolar Transistor (IGBT). The
Chopper Transistor is either ON or OFF, connecting the Dynamic Brake
Resistor to the DC bus and dissipating power, or isolating the resistor from the
DC bus. The most important rating is the collector current rating of the Chopper
Transistor that helps to determine the minimum resistance value used for the
Dynamic Brake Resistor.
Signal
Common
Dynamic
Brake
Resistor
Chopper
Transistor
Chopper Transistor
Voltage Control
To
Voltage
Control
To
Voltage
Control
– DC Bus
+ DC Bus
To
Voltage Dividers
Voltage
Divider
Voltage
Divider
FWD
FWD

Allen-Bradley 20A Specifications

General

Brand	Allen-Bradley
Model	20A
Category	Controller
Language	English