Motor Controllers AC Variable Frequency Drives
RVBS
Specifications are subjected to change without notice.10/08/2021
39
4.4.5
Anti-regenerative control
H21 specifies the anti-regenerative control. In inverters not equipped with a PWM converter or braking
resistor, if regenerative energy returned exceeds the inverter's braking capability, an overvoltage trip occurs.
In case of H21 = 1: when the DC link bus voltage exceeds the preset voltage limiting level, the inverter
lengthens the deceleration time to three times the specified time to decrease the deceleration torque to 1/3. In
this way, the inverter reduces the regenerative energy tentatively. This control applies only in deceleration.
When the load on the motor results in a braking effect, the control does not have any effect.
In case of H21 = 2 or 4: The inverter controls the output frequency to keep the braking torque at around 0
N·m in both acceleration/deceleration and constant speed running phases in order to avoid an overvoltage trip.
Since increasing the output frequency too much under anti-regenerative control is dangerous, the inverter
has a torque limiter (Frequency increment limit for braking) that can be specified by H22. The torque limiter
limits the inverter's output frequency to less than "Reference fre H22 setting."
Note that the torque limiter activated restrains the anti-regenerative control, resulting in a trip with an
overvoltage alarm in some cases. Increasing the H22 data (0.0 to 400.0 Hz) makes the anti-regenerative
control capability high.
Addition, during deceleration triggered by turning the run command OFF, the anti-regenerative control
increases the output frequency so that the inverter may not stop the load depending on the load state (huge
moment of inertia, for example). To avoid that, H21 provides a choice of cancellation of the anti-regenerative
control to apply when three times the specified deceleration time is elapsed, thus decelerating the motor.
Data for H21
Function
0
Disable
1
Enable (Lengthen the deceleration time to three times the specified time under voltage limiting control.)
4
Enable (Torque limit control: Disable force-to-stop processing.)
Function
code
Mod.
add.
Description
Def
Min
Max
U.M.
R/W
H21
0x0315
Automatic Deceleration (Anti-
regenerative control) (Mode selection)
0
0
4
-
R/W
H22
0x0316
Automatic Deceleration (Frequency
increment limit of braking)
50
0
1200
0.1Hz
R/W
