890SD Standalone Drive
890CS Common Bus Supply - Frames B & D; 890CD Common Bus Drive and 890SD Standalone Drive - Frames B, C & D
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Power Connections -
890SD Standalone Drive
BRAKE RESISTOR - information
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.
