User Manual V 1-4.XX User guide

9-4 Applications
The regenerative energy may be limited either automatically by
letting the bus regulator work along with the dynamic brake or
manually by reducing the regenerative energy. Normally, automatic
limiting by the bus voltage regulator is preferred because manual
limiting may have to be repeated if the regenerative energy changes
due to load, speed, or system losses.
To stop overvoltages automatically, you must enable the bus voltage
regulator with the dynamic brake. Follow these directions:
1. Set bit 5, Bus High Lim, in Bus/Brake Opts (parameter 13).
2. Set bit 10, Brake/Regn, in Bus/Brake Opts (parameter 13). This
sets the bus voltage regulator operation to a higher voltage.
3. If overvoltages still occur, then manually reduce the Regen Power
Lim (parameter 76). See below.
To stop overvoltages manually, you must limit the regenerated energy
by either extending the deceleration time or reducing the regenerated
power limit.
• To extend the deceleration time, set Decel Time 1 (parameter 44)
and Decel Time 2 (parameter 45) to the desired values.
• To reduce the regenerated power limit, set Regen Power Lim
(parameter 76) to the desired value.
Using the Bus Regulator for Braking
If you are not using a dynamic brake, the bus regulator is the default
braking method as selected during the Quick Start routine.
To enable bus regulator braking:
1. Clear bit 10, Brake/Regen, in Bus/Brake Opts (parameter 13).
2. Clear bit 6, Flux Braking, in Bus/Brake Opts.
3. Clear bit 5, Bus High Lim, in Bus/Brake Opts.
As the motor is decelerated or as regeneration occurs (for example, an
overhauling load), energy is transferred from the motor to the drive.
This causes an increase in the bus voltage. When the bus voltage
becomes high enough, the bus voltage regulator becomes active and
reduces the regeneration power limit to control the bus voltage. The
maximum regeneration power limit is controlled in Regen Power Lim
(parameter 76), and the bus voltage regulator automatically further
reduces this level as needed to limit the bus voltage. The regeneration
power limit implements a torque limit as a function of motor speed
times torque. Then, the system power losses determine the motor
deceleration.
The default bus regulator braking set up uses a -25% regenerative
power limit, Regen Power Lim. If the losses in the system are large
enough, you may use a larger value.
file:
Application
group:
Bus Control
file:
Control
group:
Control Limits