YASKAWA GA700 Technical Manual page 839

The occurrence of a momentary power loss is detected when the drive DC bus voltage is lower than the value set
in L2-05 [Undervoltage Detect Level (Uv1)].
0 : Disabled
Uv1 [DC Bus Undervoltage] is detected when a momentary power loss occurs.
If power is not restored within 15 ms, a Uv1 is triggered and the drive shuts off the output. The motor coasts to
stop.
1 : Enbl with Timer
The drive restarts if the power returns within the time set to L2-02 [MomentaryPowerLossRide-Thru Time]. Uv1
is detected If power is not restored within the time set to L2-02.
The drive briefly shuts off its output after a power loss. If the power returns within the time set to L2-02, the drive
will perform Speed Search and attempt to resume operation.
If the DC bus voltage continues at a state less than or equal to the detection level of Uv1 for at least the time set in
L2-02, Uv1 is detected and the drive outputs a fault signal.
Note:
• The time required for the drive to restart after power is restored varies depending on the drive capacity.
• The upper limit of the possible momentary power loss Ride-Thru time varies depending on the drive model.
2 : Enbl whl CPU act
The drive restarts if the power returns and the drive control circuit has power. This will not trigger a Uv1.
When a momentary power loss occurs, the drive output will be shut off. If the power returns and the drive control
circuit has power, the drive will attempt to perform Speed Search and resume the operation. This will not trigger a
Uv1. This function enables longer support for power loss than using L2-01 = 1.
3 : KEB Mode
Uv1 is detected when power is not restored within the time set in L2-02.
When a momentary power loss is detected, the drive decelerates using regenerative energy from the motor via the
KEB operation. When power is restored within the time set in L2-02, the drive accelerates the motor again to the
frequency reference value used before the power loss. If the power does not return within the time set to L2-02
elapses, Uv1 is detected, and the drive output will shut off. The type of KEB operation is determined by the L2-29
[KEB Method Selection].
4 : KEB Stop Mode
The drive restarts if the power returns and the drive control circuit has power.
The drive decelerates using regenerative energy from the motor until the power returns and then restarts when a
momentary power loss is detected. When power is restored during deceleration, the drive accelerates the motor
again to the frequency reference value used before the power loss. If the motor comes to a stop before the power
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.
5 : KEB Decel to Stp
Deceleration still continues after power is restored until the motor completely stops.
The drive ramps to stop using the regenerative energy from the motor when a momentary power loss is detected
Even if the power is restored, the drive will continue to decelerate until the motor comes to a complete stop. After
the power is restored, the drive ramps to stop using the selected deceleration time. The type of KEB operation is
determined by the L2-29.
Note:
Be aware of the following points when setting L2-01.
• A Momentary Power Loss Unit is available to allow for a longer momentary power loss ride through time in models 2004 to 2056 and
models 4002 to 4031. A Momentary Power Loss Unit makes it possible to continue running the drive after up to two seconds of power
loss.
• When setting L2-01 = 1 to4, keep the magnetic contactor between the motor and the drive closed and the control signal retained as long
as the drive performs KEB operation
• When L2-01 = 1 to 5, Uv [DC Bus Undervoltage] will flash on the keypad while the drive is attempting to recover from a momentary
power loss. A fault signal is not output at this time.
• When using a magnetic contactor between the motor and the drive, keep the magnetic contactor closed as long as the drive performs
KEB operation or attempts 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 setting L2-01 = 3 to 5, a Uv1 is triggered if the control power supply voltage falls below the CPU operation level during KEB
Ride-Thru.
YASKAWA ELECTRIC SIEP C710617 01B YASKAWA AC Drive GA700 Technical Manual
11.9 L: Protection Function
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