ABB ACS850-04 series, Руководство по оборудованию

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Resistor braking
155
Resistor braking
What this chapter contains
This chapter describes how to select, protect and wire brake resistors.
Availability of brake choppers and resistors
Brake choppers are optionally available as built-in units, indicated in the type
description by +D150. External resistors are available on request from ABB.
When is resistor braking needed
Typically, a drive system is equipped with brake choppers and resistors if:
• high capacity braking is needed and the drive cannot be equipped with a
regenerative supply unit
• a backup for the regenerative supply unit is needed.
Operation principle
The energy generated by the motor during a fast deceleration of the drive typically
causes the voltage to rise in the drive module intermediate DC circuit. The chopper
connects the brake resistor to the intermediate DC circuit whenever the voltage in
the circuit exceeds its maximum limit. Energy consumption by the resistor losses
lowers the voltage until the resistor can be disconnected.
Planning the braking system
Selecting the brake circuit components
1. Calculate the maximum power (P
max
) generated by the motor during braking.
2. Select a suitable drive and brake resistor combination for the application
according to the rating table on page 159 . Take also account of other factors in
the drive selection. The braking power must be greater than or equal to the
maximum power generated by the motor during braking:
3. Check the resistor selection. The energy generated by the motor during a 400-
second period must not exceed the resistor heat dissipation capacity E
R
.
Note: If the E
R
value is not sufficient, it is possible to use a four-resistor assembly
in which two standard resistors are connected in parallel, two in series. The E
R
value of the four-resistor assembly is four times the value specified for the
standard resistor.
P
br
> P
max