Motor Controllers AC Variable Frequency Drives
RVBS
Specifications are subjected to change without notice.10/08/2021
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works, and the output frequency of the inverter automatically decreases. When the output frequency
matches the motor speed, the motor accelerates up to the original output frequency. See the figure
below. In this case, the instantaneous over-current limiting must be enabled (H07 = 1).
< Restart sequence after momentary power failure with motor speed >
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Restart mode after momentary power failure (Restart time) (H25)
H25 specifies the time period from momentary power failure occurrence until the inverter reacts for
restarting process.
If the inverter starts the motor while motor’s residual voltage is still in a high level, a large inrush
current may flow, or an overvoltage alarm may occur due to an occurrence of temporary regeneration.
For safety, therefore, it is advisable to set H25 to a certain level so that restart will take place only
after the residual voltage has dropped to a low level. Note that even when power is restored, restart
will not take place until the restart time (H25) has elapsed.
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Factory default
By factory default, H25 is set at one of the values shown below according to the inverter capacity.
Basically, you do not need to change H25 data. However, if the long restart time causes the flow rate
of the pump to overly decrease or causes any other problem, you might as well reduce the setting to
about a half of the default value. In such a case, make sure that no alarm occurs.
Inverter capacity (kW)
Factory default of H25 (Restart time in seconds)
0.1 to 7.5
0.5
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Restart mode after momentary power failure (Frequency fall rate) (H26)
During restart after a momentary power failure, if the inverter output frequency and the idling motor
speed cannot be harmonized with each other, an over-current will flow, activating the over-current
limiter. If it happens, the inverter reduces the output frequency to match the idling motor speed
according to the reduction rate (Frequency fall rate: Hz/s) specified by H26.
