User Manual Instruction Manual

Application Notes
13-61
Without bus regulation, if the bus voltage exceeds the operating limit established by
the power components of the drive, the drive will fault, shutting off the output devices
to protect itself from excess voltage.
With bus regulation enabled, the drive can respond to the increasing voltage by
advancing the output frequency until the regeneration is counteracted. This keeps the
bus voltage at a regulated level below the trip point.
Since the same integrator is used for bus regulation as for normal frequency ramp
operation, a smooth transition between normal frequency ramp operation and bus
regulation is accomplished.
The regulator senses a rapid rise in the bus voltage and activates prior to actually
reaching the internal bus voltage regulation set point Vreg. This is important since it
minimizes overshoot in the bus voltage when bus regulation begins thereby attempting
to avoid an over-voltage fault.
The bus voltage regulation set point (Vreg) in the drive is fixed for each voltage class
of drive. The bus voltage regulation set points are identical to the internal dynamic
brake regulation set points VDB's.
0V Fault @V
bus
Max
Drive Output Shut Off
Ch1
Ch3
Single Seq 500 S/s
100mV
500mV
Ch2 100mV M 1.00s Ch3 1.47
V
3
2
1
DB Bus
Motor Speed
Output Frequency