5-23
This setting is optimal for operations in which the motor speed quickly slows down
to 0 r/min due to the heavy load with a very small moment of inertia if the motor
coasts to a stop because of the momentary power failure.
• There is a 0.5-second delay from detection of the undervoltage until
the motor is restarted This delay is due to the time required for the
residual electricity (magnetic flux) in the motor to drop sufficiently.
Therefore, even if the momentary power failure period is shorter
than 0.5 second, a delay of at least 0.5 second is required for the
motor to restart.
• When a momentary power failure occurs, the power supply voltage fo
external circuitry (such as relay circuits) controlling the inverter may
also drop as low as to cause run commands to be discontinued.
Therefore, during recovery from a momentary power failure, the in-
verter waits 2 seconds for a run command to arrive. If it receives one
within 2 seconds, it will restart. If a run command arrives more than 2
seconds later, then the inverter should be restarted at the starting
frequency (F23). The external circuitry should be so designed that it
will issue a run command within 2 seconds in such an event; otherwise
it should incorporate a relay with a mechanical locking feature.
• If a coast-to-stop command BX is issued during the time from the
detection of a momentary power failure to restart, the inverter exits
from the state of waiting for restarting, and enters Running mode. I
any run command is issued, the inverter will start at the starting fre-
quency (F23) preset.
If you select restart after momentary power failure (F14 = 4 or 5), the inverter will
automatically restart running the motor when power is recovered.
The machine should be so designed that human body and peripheral equipment
safety is ensured even after automatic restarting.
Otherwise an accident could occur.
F15, F16 Frequency Limiter (High and Low)
Frequency limiter (high) F15 sets the upper limit of the output frequency, while
frequency limiter (low) F16 sets the lower limit of the output, as shown below.
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