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Even if selecting "Trip after decelerate-to-stop" or "Continue to run," the inverter may not be able to do so
when the load's inertia is small or the load is heavy, due to undervoltage caused by a control delay. In
such a case, when "Trip after decelerate-to-stop" is selected, the inverter allows the motor to coast to a
stop; when "Continue to run" is selected, the inverter saves the output frequency being applied when the
undervoltage alarm occurred and restarts at the saved frequency after a recovery from the momentary
power failure.
When the input power voltage for the inverter is high, setting the continuous running level high makes the
control more stable even if the load's inertia is relatively small. Raising the continuous running level too
high, however, might cause the continuous running control activated even during normal operation.
When the input power voltage for the inverter is extremely low, continuous running control might be
activated even during normal operation, at the beginning of acceleration or at an abrupt change in load.
To avoid this, lower the continuous running level. However, possible undervoltage results from voltage
drop due to a control delay if set too low.
Changing the continuous running level, make sure that the continuous running control will be performed
properly, by considering the fluctuations of the load and the input voltage.
F15, F16
Frequency Limiter (High), Frequency Limiter (Low)
H63 Low Limiter (Mode selection)
Frequency Limiter (High and Low) (F15, F16)
Data setting range: 0.0 to 500.0 (Hz)
F15 and F16 specify the upper and lower limits of the output frequency or reference frequency, respectively. The
frequency to which the limit is applied differs depending on the control system, as seen in the table.
Frequency Limiter
Frequency to which the limit is applied
V/f control
Vector control without/with speed sensor
Frequency Limiter (High)
F15
Output frequency
Reference speed (reference frequency)
Frequency Limiter (Low)
F16
Reference frequency
Reference speed (reference frequency)
When the limit is applied to the reference frequency or reference speed, delayed responses of
control may cause an overshoot or undershoot, and the frequency may temporarily go beyond the
limit level.
Low Limiter (Mode selection) (H63)
H63 specifies the operation to be carried out when the reference frequency drops below the low level specified by
F16, as follows:
Data for H63
Operation
0
The output frequency will be held at the low level specified by F16.
1
The inverter decelerates to stop the motor.
(H63 = 0)
(H63 = 1)
• When changing the frequency limiter (High) (F15) in order to raise the reference frequency, be sure to
change the maximum frequency (F03) accordingly.
• Maintain the following relationship among the data for frequency control:
F15 > F16, F15 > F23, and F15 > F25
F03 > F16
where, F23 and F25 specify the starting and stop frequencies, respectively.
If any erroneous data for these function codes is entered, the inverter may not run the motor at the
desired speed, nor start it normally.
