YASKAWA GA700 Technical Manual page 956

11.9 L: Protection Functions
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Stall Prevention
If the load is too heavy or the acceleration and deceleration times are too short, the motor can slip too much
because it cannot work at the same rate as the frequency reference. If the motor stalls during acceleration, current
increases as the slip increases to cause an oC [Overcurrent], oL2 [Drive Overload], or oL1 [Motor Overload] and
the drive will stop. If the motor stalls during deceleration, too much regenerative power will flow back into the
DC bus capacitors, and cause the drive to fault out from ov [Overvoltage] and the drive will stop.
The stall prevention function will let the motor get to the set speed without stalling and it is not necessary for you
to change the acceleration or deceleration time settings. You can set a separate stall prevention functions for
acceleration, operating at constant speeds, and deceleration.
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Overvoltage Suppression Function
Decreases the regenerative torque limit and increases the output frequency when the DC bus voltage increases to
prevent ov. This function can drive loads with cyclic regenerative operation, for example punch presses or other
applications with repeated crank movements. When you use this function, set L3-11 = 1 [Overvoltage Suppression
Select = Enabled].
The drive adjusts the regenerative torque limit and the output frequency during overvoltage suppression to make
sure that the DC bus voltage is not more than the level set in L3-17 [DC Bus Regulation Level].
Set these parameters as necessary when you use the overvoltage suppression function:
• L3-20 [DC Bus Voltage Adjustment Gain]
• L3-21 [OVSuppression Accel/Decel P Gain]
• L3-24 [Motor Accel Time @ Rated Torque]
• L3-25 [Load Inertia Ratio]
Note:
• When overvoltage suppression is triggered, the motor speed is more than the frequency reference. Do not use overvoltage suppression
for applications where the frequency reference and the motor speed must align.
• When you use a braking resistor, set L3-11 = 0 [Disabled].
• The overvoltage suppression function is enabled only when you operate immediately below the maximum frequency. Overvoltage
suppression does not increase the output frequency to more than the maximum frequency. Make sure that the motor and machine
specifications are correct for the application, then increase the maximum frequency.
• If there is a sudden increase to a regenerative load, ov can occur.
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L3-01: Stall Prevention during Accel
No.
Name
(Hex.)
L3-01 Stall Prevention
during Accel
(048F)
Note:
When A1-02 = 5 [Control Method Selection = PM Open Loop Vector], the setting range is 0 and 1 .
Stall prevention during acceleration will not let motors stall or stop when the drive detects oC [Overcurrent], oL2
[Drive Overload], or oL1 [Motor Overload] and large loads are applied during acceleration or when setting
sudden acceleration times regarding load inertia.
0 : Disabled
The Stall Prevention function does not operate during acceleration, and acceleration occurs for the set acceleration
time. If the acceleration time is too short, the motor does not fully accelerate during the set time, which causes the
drive to detect oL1 or oL2 and the motor to stop.
1 : Enabled
Enables the Stall Prevention During Acceleration function. Operation is different for different control methods.
• V/f Control, Open Loop Vector Control, or EZ Open Loop Vector Control
When the output current is more than the value set in L3-02 [Stall Prevent Level during Accel], the drive stops
acceleration. When the output current is less than the value set in L3-02 - 15%, the drive starts to accelerate
again. The Stall Prevention function level automatically falls for constant output ranges.
956
V/f CL-V/f OLV CLV AOLV
Sets the method of the Stall Prevention During Acceleration.
YASKAWA ELECTRIC SIEP C710617 05F YASKAWA AC Drive GA700 Technical Manual
Description
OLV/PM AOLV/PM CLV/PM EZOLV OLV/PM
Default
(Range)
1
(0 - 3)