User Manual V 1-4.XX User guide

Applications 9-5
Figure 9.1 shows how the bus regulator relates to both speed and
torque.
Figure 9.1
Bus Regulator in Relation to Speed and Torque
Using Flux Braking
You can use flux braking to stop the drive or to shorten the
deceleration time to a lower speed. The higher losses result in a
shorter motor deceleration time. Other methods of deceleration or
stopping may perform better depending on the motor and the load.
To enable flux braking:
1. Set bit 6, Flux Braking, in Bus/Brake Opts (parameter 13).
1. Clear bit 10, Brake/Regen, in Bus/Brake Opts.
1. Clear bit 5, Bus High Lim, in Bus/Brake Opts.
As the motor is decelerated or as regeneration occurs, energy is
transferred from the motor to the drive. This increases 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.
When enabled, flux braking automatically increases the motor flux
resulting in an increase of motor losses. The flux current is only
increased when the bus voltage regulator is active. When the bus
voltage regulator is not active, the flux current is returned to normal.
The maximum flux current is equal to rated motor current but may be
further reduced depending on the load level, IT protection, or current
limits. In general, the flux current is not increased when the motor is
at or above rated speed. At higher speeds, field weakening is active
and the motor flux current cannot be increased. As the speed
decreases below base speed, the flux current increases until there is
enough voltage margin to run rated motor current.
0
V
Bus
Speed
Torque
System Losses
file:
Application
group:
Flux Braking
file:
Control
group:
Control Limits