2.9 L: Protection Functions
374 YASKAWA TOEPYAIGA5002A GA500 DRIVE PROGRAMMING
If the voltage level increases, the drive momentarily holds the frequency to prevent an ov before it continues to
decelerate.
Note:
When you cannot use a dynamic braking option, use System KEB Ride-Thru.
■ L2-30: KEB Zero Speed Operation
No.
(Hex.)
Name Description
Default
(Range)
L2-30
(045E)
Expert
KEB Zero Speed Operation
Sets the operation when the output frequency decreases below the zero level (DC braking injection
starting frequency) during KEB deceleration when L2-01 = 3 to 5 [Power Loss Ride Through Select
= Kinetic Energy Backup: L2-02, Kinetic Energy Backup: CPU Power, or Kinetic Energy Backup:
DecelStop].
0
(0, 1)
0 : Baseblock
1 : DC/SC Braking
Does DC injection braking and short circuit braking as specified by b2-04 [DC Inject Braking Time at Stop] and b2-
13 [Short Circuit Brake Time @ Stop].
■ L2-31: KEB Start Voltage Offset Level
No.
(Hex.)
Name Description
Default
(Range)
L2-31
(045D)
Expert
KEB Start Voltage Offset
Level
Sets the KEB start voltage offset.
Determined by A1-02
(200 V Class: 0 - 100 V,400
V Class: 0 - 200 V)
The drive uses this formula to calculate the KEB start voltage:
KEB start voltage = L2-05 [Undervoltage Detect Level (Uv1)] + L2-31
◆ L3: Stall Prevention
L3 parameters set the Stall Prevention function and overvoltage suppression function.
■ 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 detect an ov [Overvoltage] fault and 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.
■ 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]
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