L3: Stall Prevention - Omron Q2A Series Technical Manual

returns, the drive loses control power and the drive output shuts off. A Uv1 is not triggered when power is restored
while power to the CPU in the drive is maintained. The type of KEB operation is determined by L2-29.
4 : KEB Decel to Stop
When power returns, the drive will continue to decelerate until the motor fully stops.
If the drive detects momentary power loss, the drive will use regenerative energy from the motor and ramp to
stop. When you return power to the drive, the drive will continue to decelerate until the motor comes to a full
stop. After you return power, the drive will ramp to stop in the set deceleration time. L2-29 sets the type of KEB
operation.
Note:
When you set L2-01 and L2-50, make sure that you know these items:
• You can use a Momentary Power Loss Unit on models 2004 to 2056 and 4002 to 4031 for a longer momentary power loss ride through
time. A Momentary Power Loss Unit makes it possible to continue operation of the drive after a maximum of 2 seconds of power loss.
• When you set L2-01 = 1 and L2-50 = 0 to 3, keep the magnetic contactor between the motor and the drive closed and keep the control
signal while the drive does KEB operation.
• When you set L2-01 = 1 and L2-50 = 1 to 4, Uv [Undervoltage] will flash on the keypad while the drive tries to recover from a
momentary power loss. The drive will not output a fault signal at this time.
• When you use a magnetic contactor between the motor and the drive, keep the magnetic contactor closed while the drive does KEB
operation or tries to restart with Speed Search.
• Keep the Run command active during KEB operation. The drive cannot accelerate back to the frequency reference when the power
returns.
• When you set L2-01 = 1 and L2-50 = 2 to 4, if the control power supply voltage is less than the CPU operation level during KEB Ride-
Thru, it will trigger Uv1.
◆

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 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.
■
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 [Overvolt Supression
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 [DCBus Regul.Level].
Set these parameters as necessary when you use the overvoltage suppression function:
• L3-20 [DCBus VoltAdj Gain]
• L3-21 [OVSup Acc/Dec Gain]
• L3-24 [Acc@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.
SIEPYEUOQ2A01A AC Drive Q2A Technical Manual
12.8 L: PROTECTION
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