LG C Series - Manual (Page 93)

10. Advanced functions

H23: It limits the current during Speed search. Set as the percent of H33 – [Motor rated
current].
 H24, H25: Speed search is activated via PI control. Adjust P gain and I gain corresponding
to the load characteristics.

I54, I55: Signal of active Speed search is given to external sequence via Multi-function
output terminal (MO) and Multi-function relay output (30AC).

EX) Speed search during Instant Power Failure restart
Input
voltage
Frequency
Voltage
Current
H23
t1 t2
Multi-function
output or
Relay
ƒ When the input power is cut off due to instant power failure, the inverter
outputs Low voltage trip (LV) to hold the output.
ƒ When the power is restored, the inverter outputs the frequency before the
low voltage trip and the voltage is increased due to PI control.
ƒ t1: If the rise in current is greater than the preset level in H23, the rise in
voltage will stop and the frequency is decreased.
ƒ t2: If the opposite of t1 occurs, the increase in voltage starts again and the
decrease in frequency stops.
ƒ When the frequency and voltage are restored back to the nominal level,
acceleration will continue at the frequency before trip.

Speed search is suitable operation when load inertia is large. It is highly
recommended to restart after stopping the motor when the load inertia is great.
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