
890CS & 890CD Common Bus Units
890CS Common Bus Supply - Frames B & D; 890CD Common Bus Drive and 890SD Standalone Drive - Frames B, C & D
Page
4-17
8
9
10
11
A
B
C
D
1
2
3
4
5
6
7
E
8
9
1
2
3
4
5
6
E
Power Connections - 890CS Common Bus Supply
EXTERNAL BRAKE RESISTOR - Option
DBR+ DBR-
You can connect an external brake resistor between terminals DBR+ and DBR-.
DO NOT apply external voltage sources (mains supply or otherwise) to the braking
terminals.
Maximum wire size:
16mm
2
/ 6AWG 1.2Nm / 0.9lbf
During deceleration, or with an overhauling load, the motor acts as a generator.
Energy flows back from the motor into the dc link capacitors within the drive. This
causes the dc link voltage to rise. If the dc link voltage exceeds 810V for the 400V
build (or 890V for the 500V build) then the drive will trip to protect the capacitors
and the drive power devices. The amount of energy that can be absorbed in the
capacitors is relatively small; typically more than 20% braking torque will cause the
drive to trip on overvoltage. Dynamic braking increases the braking capability of the
drive by dissipating the excess energy in a high power resistor connected across the
dc link, see above.
When the dc link voltage rises above that specified for each Frame size the brake
unit switches the external resistor network across the dc link. The brake unit switches
off again when the dc link voltage falls below the threshold level. The amount of
energy produced by the motor during regeneration depends upon the DECEL TIME
parameter (refer to the REFERENCE RAMP and DYNAMIC BRAKING function
blocks) and the inertia of the load.
Refer to Chapter 6:"Associated Equipment" for brake resistor selection.