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Overvoltage Suppression Function
Suppresses overvoltage faults by decreasing the regenerative torque limit and slightly increasing the output frequency when
the DC bus voltage rises. This function can drive loads with cyclic regenerative operation, such as a punch press or other
applications that involve repetitive crank movements.
The regenerative torque limit and the output frequency are adjusted during ov suppression so that the DC bus voltage does
not exceed the level set to parameter L3-17. In addition to the parameters explained below, ov suppression also uses these
settings for frequency adjustment:
• DC bus voltage gain (L3-20)
• Deceleration rate calculations gain (L3-21)
• Inertia calculations for motor acceleration time (L3-24)
• Load inertia ratio (L3-25)
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 the application requires this, increase the maximum frequency and change the base frequency
setting.
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L3-11: Overvoltage Suppression Function Selection
Enables or disables the overvoltage suppression function.
No. Name Setting Range Default
L3-11 Overvoltage Suppression Function Selection 0, 1 0
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 dynamic 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.
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L3-17: Target DC Bus Voltage for Overvoltage Suppression and Stall Prevention
Sets the target DC bus voltage level used by the overvoltage suppression function (L3-11 = 1), Intelligent Stall Prevention
during deceleration (L3-04 = 2).
No. Name Setting Range Default
L3-17
Target DC Bus Voltage for Overvoltage Suppression
and Stall Prevention
431.3 to 1150 Vdc
1064 Vdc
<1>
<1> This value is initialized when E1-01 is changed.
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L3-20: DC Bus Voltage Adjustment Gain
Determines the proportional gain used by overvoltage suppression (L3-11 = 1), Single Drive KEB 2 (L2-29 = 1), KEB Ride-
Thru 2 (H1-oo = 7A or 7B) ,and Intelligent Stall Prevention during deceleration (L3-04 = 2) to control the DC bus voltage.
No. Name Setting Range Default
L3-20 DC Bus Voltage Adjustment Gain 0.00 to 5.00
Determined by
A1-02
Adjustment for Single Drive KEB 2 (L2-29 = 1) and Intelligent Stall Prevention During Deceleration
• Increase this setting slowly in steps of 0.1 if overvoltage or undervoltage occurs at the beginning of deceleration.
• Decrease this setting if there is a fair amount of speed or torque ripple.
Adjustment for Overvoltage Suppression
• Increase this setting slowly in steps of 0.1 if overvoltage suppression is enabled (L3-11 = 1) and a sudden increase in a
regenerative load causes an overvoltage fault.
• Decrease this setting if there is a fair amount of speed or torque ripple.
5.8 L: Protection Functions
254
YASKAWA ELECTRIC SIEP C710616 31B YASKAWA AC Drive – A1000 Technical Manual
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