gefran VDI100 Series Instruction Manual page 230

Overvoltage suppression is used for the application of likely causing to energy recharge.
Example: there are two situations causing excessive energy to recharge the inverter in stamping application
(1) When cam clutch is not engaged, the motor will accelerate and start flywheel. When motor decelerates,
the rotation speed will higher than motor speed owing to the large flywheel's inertia and then recharge the
inverter.
(2) When cam clutch is engaged, the motor will start flywheel and compress the spring. When the highest point
of the cam moves beyond its center, the spring will release the power to the flywheel and excessive energy
output recharge the inverter.
Over-voltage prevention (OVP) function monitors the DC-bus voltage and adjusts the speed reference, acceler-
ation and deceleration rate, to prevent the inverter from tripping on an overvoltage.
When the speed reference is reduced, the motor will start to decelerate. When the inverter is operating at a
fixed output frequency and excessive regenerative energy back to the inverter is detected the inverter will ac-
celerate the motor in order to reduce the DC-bus voltage. Refer to figure 4.4.91.
When 11-40=1: OV prevention Mode 1
1) DC voltage filter is used to provide a stable reference value for determining the change in DC voltage
change during regenerative operation.
- Adjust the DC voltage filtering increase rate parameter 11-33 (DC Voltage Filter Rise Amount). When the
DC voltage exceeds 11-33 +11-35 (DC Voltage Filter Deadband Level), the output of the filter will increase.
- Adjust the DC voltage filtering decrease rate parameter 11-34 (DC Voltage Filter Fall Amount). When the
DC voltage exceeds 11-33 +11-35 (DC Voltage Filter Deadband Level), the output of the filter will decrease.
- Monitor the DC voltage filter output by 12-20 (DC voltage filter value).
- Set the DC voltage filter decrease rate (11-34) to a greater value than the value of the DC voltage filtering
increase rate (11-33).
230
Figure 4.4.90 Stamping Operation
Inverter
Motoring : f
Overhauling : f
DC bus
voltage
12-20
DC bus +
voltage
-
DC bus filter
11-33 11-36
11-34
Gain
11-35
OVP 2
accel /
decel
time
11-28
OVP2
Gain
Gear
f
out
box
f
motor
Motor
> f
out motor
< f
out motor
Figure 4.4.91 OVP operation
Output Frequency
SFS
Fout
Frequency
Reference
OVP
11-40 = 1
11-37
accel /
decel
time
Frequency
Reference
Limit
11-37
FLYWHEEL
cam
clutch
After SFS
11-40= 0
Output
Frequency
11-40 = 1 or 2
+
+
11-40 = 2
VDI100 • Instruction manual