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This function selects operation if a momentary power failure occurs.
The function for detecting power failure and activating protective operation (i.e., alarm output, alarm display, inverter
output cutoff) for undervoltage can be selected. The automatic restart function (for automatically restarting a coasting
motor without stopping) when the supply voltage is recovered can also be selected.
When setting value is selected "2" or "3", both integration constant and the proportional constant during operation
ride-though can be adjusted by the function code : U23 and U24. The details are referred to the function code : U23 and
U24.
Setting range: 0 to 5
The following table lists the function details.
F14
Restart mode after momentary power failure
Set
value
Function name Operation at power failure Operation at power recovery
０
Inactive
(immediate inverter trip)
If undervoltage is detected, the drive will immediately trip and
an undervoltage fault (LU) is displayed. The drive output
stops and the motor will coast to a stop.
The drive operation is not automatically
restarted. Input a reset command and
operation command to restart operation.
１
Inactive
(inverter trip at recovery)
If undervoltage is detected, the drive output stops and the
motor will immediately coast to a stop. A drive fault is not
activated
An undervoltage fault (LU) is activated at
power recovery. Drive operation is not
automatically restarted. Input a reset
command to restart operation.
２
Inactive
(inverter trip after
deceleration to a stop at
power failure)
Note1
When the DC bus voltage reaches the continue operation
voltage level (H15), a controlled deceleration to a stop occurs.
The inverter collects the inertia energy of the load to maintain
the DC bus voltage and controls the motor until it stops, then
an undervoltage fault (LU) is activated.
The drive will automatically decrease the deceleration time if
necessary. If the amount of inertia energy from the load is
small, and the undervoltage level is achieved before the motor
stops, the undervoltage fault is immediately activated and the
motor will coast to a stop.
The drive operation is not automatically
restarted. Input a reset command and
operation command to restart operation.
３
Active
(operation ride through,
for high-inertia loads)
Note1
When the DC bus voltage reaches the continue operation
voltage level (H15), energy is collected from the inertia of the
load to maintain the DC bus voltage and extend the ride
through time. The drive will automatically adjust the
deceleration rate to maintain DC bus voltage level. If
undervoltage is detected, the protective function is not
activated, but drive output stops and the motor coast to a stop.
Operation is automatically restarted.
For power recovery during ride-through the
drive will accelerate directly to the original
frequency. If undervoltage is detected,
operation automatically restarts with the
frequency at the time that the undervoltage
is detected.
４
Active
(restart with the
frequency at power
failure)
Note1
If undervoltage is detected, the protective function is not
activated. The drive output stops and the motor will coast to a
stop.
Operation is automatically restarted with
the frequency at power failure.
５
Active
(restart with the start
frequency, for low-inertia
loads)
Note1
If undervoltage is detected, the protective function is not
activated, but output stops.
Operation is automatically restarted with
the frequency set by F23, "Starting
frequency."
Note1) When the function code H18(Torque control) is excluding "0" and Motor 1 is selected, the inverter will trip at power
recovery if function code F14 is set to between "2" and "5". This operation is same as F14 is set to "1".
Function codes H13 to H16 are provided to control a restarting operation after momentary power failure. These functions
should be understood and used. The pick-up (speed search) function can also be selected as a method of restarting when
power is recovered following a momentary failure. (For setting details, see function code H09.)
The pick-up function searches for the speed of the coasting motor to restart the motor without subjecting it to excessive shock.
In a high-inertia system, the reduction in motor speed is minimal even when the motor is coasting. A speed searching time is
required when the pick-up function is active. In such a case, the original frequency may be recovered sooner when the function
is inactive and the operation restarted with the frequency prior to the momentary power failure.
The pick-up function works in the range of 5 to 100 Hz. If the detected speed is outside this range, restart the motor using the
regular restart function.
WARNING
• Automatically restart could be provided at power recovered, if "Restart mode after
momentary power failure" is valid.
• The machine should be designed to securing the human safe even restarting.
Accident may result.
F 1 4 R E S T A R T
Related functions:
U23, U24