5.8  L: Protection Functions
YASKAWA ELECTRIC SIEP C710616 35D YASKAWA AC Drive E1000 Technical Manual  215
Setting 2: Recover as long as CPU has power
When a momentary power loss occurs, the drive output will be shut off. Should the power return as long as the drive 
control circuit has power, th
e drive will attempt to perform Speed Search and resume the operation. A Uv1 fault is not 
triggered.
Setting 3: KEB Ride-Thru operation within L2-02
The drive decelerates using regenerative energy from the motor until the time set in L2-02 has expired. It then tries to 
accelerate back to the frequency reference. If the power does not returned within the time set in L2-02, an Uv1 fault is 
triggered and the drive output shuts off. The type of KEB operation is determined by the setting of L2-29.
Setting 4: KEB Ride-Thru as long as CPU has power
The drive decelerates using regenerative energy from the motor until the power returns and then restarts. If the motor has 
come to a stop before, the power returns. If the drive control power gets lost, the drive output will shut off. A Uv1 fault is 
not triggered. The type of KEB operation is determined by the setting of L2-29.
Setting 5: Ramp to stop with KEB deceleration
The drive ramps to stop using the regenerative energy from the motor. Even if the power is restored, the drive will 
continue decelerating until it brings the motor to a complete stop. The type of KEB operation is determined by the setting 
of parameter L2-29. Note that if an input terminal set for KEB 1 (H1- = 65, 66) is triggered while the drive is 
decelerating, then it will accelerate back up to speed when the input is released.
Notes on Settings 1 through 5
• “Uv” will flash on the operator while the drive is attempting to recover from a momentary power loss. A fault signal is 
not output at this time.
• A Momentary Power Loss Unit is available to allow for a longer momentary power loss ride through time in the drive 
model CIMR-E2A0004 through 2A0056 and CIMR-E4A0002 through 4A0031. This option makes it possible to 
continue running after up to two seconds of power loss.
• When a magnetic contactor between motor and drive is used, be sure that the magnetic contactor remains closed as 
long as the drive performs KEB operation or attempts to restart with Speed Search.
• Make sure the Run command is kept active during KEB operation. Otherwise the drive cannot accelerate back to the 
frequency reference when the power returns.
• When L2-01 is set to 3, 4, or 5, KEB Ride-Thru will be executed as specified in L2-29.
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KEB Ride-Thru Function
When power loss is detected, the Kinetic Energy Backup Ride-Thru function (KEB Ride-Thru) decelerates the motor and 
uses regenerative energy to keep the main circuit operating. Despite power loss, the drive output is not interrupted.
Single Drive KEB Ride-Thru 1 (L2-29 = 0)
Once KEB Ride-Thru begins, the drive uses regenerative energy from the motor to keep the DC bus voltage at the level 
set to L2-11 while adjusting the rate of deceleration based on the time set to L2-06.
Note: If undervoltage occurs in the DC bus (Uv1), shorten the KEB deceleration time (L2-06). If overvoltage occurs (oV), increase the 
KEB deceleration time.
Single Drive KEB Ride-Thru 2 (L2-29 = 1)
The drive uses information about the inertia of the connected machinery to determine the deceleration rate necessary to 
keep the DC bus voltage at the level set in parameter L2-11. The resulting deceleration time is calculated based on the 
system inertia and cannot be adjusted.
No. Name Setting Range Default
L2-29 KEB Ride-Thru Function 0, 1 0
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