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Resistor braking
Contents of this chapter
The chapter describes how to select the brake resistor and cables, protect the
system, connect the brake resistor and enable resistor braking.
Safety
WARNING!
Do not do work on the brake resistor or the resistor cable when the drive is
energized. A dangerous voltage is present in the resistor circuit, even when
the brake chopper is not operating, or when it is disabled by a parameter.
Operation principle
The brake chopper handles the extra energy generated by motor during a quick
deceleration. The extra energy increases the drive DC link voltage. The chopper
connects the brake resistor to the DC link whenever the voltage is greater than
the limit defined by the control program. Energy consumption by the resistor
losses lowers the voltage until the resistor can be disconnected.
Selecting the brake resistor
Drives have a built-in brake chopper as standard equipment. The brake resistor is
selected using the table and equations shown in this section.
1.
Determine the required maximum braking power P
P
must be smaller than P
Rmax
. Refer to
Reference brake resistors (page
BRmax
Resistor braking 153
11
for the application.
Rmax
155).
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