5.8 L: Protection Functions
222 YASKAWA ELECTRIC SIEP C710616 30B YASKAWA AC Drive T1000A Technical Manual
n Overvoltage Suppression Function
This function suppresses overvoltage faults by decreasing the regenerative torque limit and slightly increasing the output
frequency when the DC bus voltage rises. It can be used to drive loads with cyclic regenerative operation, such as a
punch press or other applications that involve repetitive crank movements.
The overvoltage suppression function controls the output frequency (in V/f Control and other control modes that do not
rely on motor feedback) or the regen torque limit (in closed-loop setups) in order to keep the DC bus voltage at the value
set to L3-17.
Note: 1. The motor speed will exceed the frequency reference when overvoltage suppression is triggered. Consequently, overvoltage
suppression is not appropriate in applications that require a perfect match between the frequency reference and the motor speed.
2. Disable overvoltage suppression when using a braking resistor.
3. Overvoltage may still occur if there is a sudden increase to a regenerative load.
4. This function is enabled only when operating just below the maximum frequency. Overvoltage suppression does not increase the
output frequency beyond the maximum frequency. If this is required by the application, increase the maximum frequency and change
the base frequency setting.
n L3-11: Overvoltage Suppression Function Selection
Enables or disables the overvoltage suppression function.
Setting 0: Disabled
The regenerative torque limit and the output frequency are not adjusted. A regenerative load may trip the drive with an
overvoltage fault. Use this setting if braking options are installed.
Setting 1: Enabled
When the DC bus voltage rises due to regenerative load, an overvoltage fault is prevented by decreasing the regenerative
torque limit and increasing the output frequency.
n
L3-17: Target DC Bus Voltage for Overvoltage Suppression and Stall Prevention
Sets the target DC bus voltage target level used by the overvoltage suppression function (L3-11 = 1) or Intelligent Stall
Prevention during deceleration (L3-04 = 2).
n
L3-26: Additional DC Bus Capacitors
Sets the capacity of any additional DC bus capacitors that have been installed.
This data is used in the Power KEB, Intelligent Stall Prevention and Overvoltage Suppression functions. This setting
needs to be adjusted only if external capacity is connected to the drive's DC bus and one of these functions is used.
The resulting DC bus capacity, used by the drive will be L3-26 + S6-01.
n
L3-27: Stall Prevention Detection Time
Sets a delay time from when the Stall Prevention level is reached and the actual Stall Prevention function is activated.
No. Name Setting Range Default
L3-11 Overvoltage Suppression Function Selection 0 or 1 0
No.
<1> Values are for 200 V class drives and must be doubled for 400 V class drives.
<2> This value is initialized when E1-01 is changed.
Name Setting Range Default
L3-17 Target DC Bus Voltage for Overvoltage Suppression and Stall Prevention 150 to 400 Vdc <1> 375 Vdc <1> <2>
No. Name Setting Range Default
L3-26 Additional DC Bus Capacitors 0 to 65000 μF
0 μ
F
No. Name Setting Range Default
L3-27 Stall Prevention Detection Time 0 to 5000 ms 50 ms
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