Dynamic Brake Components - Allen-Bradley PowerFlex 70 Reference Manual

1-2 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 1.1
Figure 1.1 Simplified Dynamic Brake Schematic
+ DC Bus
Chopper Transistor
– DC Bus
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.
shows a simplified Dynamic Braking schematic.
Dynamic
Brake
Resistor
Chopper
To
Transistor
Voltage Dividers
Voltage Control
FWD
Voltage
Divider
To
Voltage
Control
Signal
Common
FWD
To
Voltage
Control
Voltage
Divider