Resistor Braking; What This Chapter Contains; Brake Choppers And Resistors With The Acs850-04; Brake Choppers - ABB ACS850-04 Hardware Manual

Resistor braking

What this chapter contains

This chapter describes how to select, protect and wire brake choppers and resistors.
The chapter also contains the technical data.

Brake choppers and resistors with the ACS850-04

Brake choppers

The ACS850-04 (frame A...D) drives have a built-in brake chopper as standard
equipment to handle the energy generated by a decelerating motor.
When the brake chopper is enabled and a resistor connected, the chopper will start
conducting when the DC link voltage of the drive reaches U
maximum braking power is achieved at U

Brake resistor selection

To select a brake resistor:
1. Calculate the maximum power generated by the motor during braking.
2. Calculate the continuous power based on the braking duty cycle.
3. Calculate the braking energy during the duty cycle.
Pre-selected resistors are available from ABB as shown in the table on page 115. If
the listed resistor is not sufficient for the application, a custom resistor can be
selected within the limits imposed by the internal brake chopper of the ACS850-04.
The following rules apply:
• The resistance of the custom resistor must be at least R
capacity with different resistance values can be calculated from the following
formula
WARNING! Never use a brake resistor with a resistance below the value specified
for the particular drive type. The drive and the chopper are not able to handle the
overcurrent caused by the low resistance.
U = 1.35 × Used AC supply voltage
DC
U = 1.25 × U
DC_BR DC
:
(U + 30 V)
DC_BR
Pmax <
R
+ 30 V.
DC_BR
2
- 30 V. The
DC_BR
. The braking power
min
Resistor braking
113