5.3 Description of Function Codes 5.3.5 H codes (High performance functions)
Starting mode (auto search delay time 1) (H49)
• Data setting range: 0.0 to 10.0 (s)
Auto search does not function normally when performed with the residual voltage remaining in the motor.
Accordingly, time to allow the residual voltage to disappear must be ensured.
When operation is started by turning a run command ON, auto search is started after the period specified with the
starting mode (auto search delay time 1) (H49) has elapsed. When switching between two inverters for controlling
one motor and if the motor is coasting to stop at the time of switching to start by auto search, by specifying H49
eliminates the need for timing the run command.
Starting mode (auto search delay time 2) (H46)
• Data setting range: 0.1 to 20.0 (s)
At the restart after a momentary power failure, at the start by turning the terminal command “BX” (“Coast to a stop”)
OFF and ON, or at the restart by auto-reset, the inverter applies the delay time specified by H46. Even if starting
conditions are satisfied, the inverter does not start unless auto-search delay time elapses after inverter goes into
OFF state. The inverter starts after elapse of auto search delay time.
Under auto search control, the inverter searches the motor speed with the voltage applied at the motor start and
the current flowing in the motor, based on the model built with the motor parameters. Therefore, the search is greatly
influenced by the residual voltage in the motor.
H46 is available for motor 1 only. At factory shipment, H46 data is preset to a correct value according to the motor
capacity for the general-purpose motor, and basically there is no need to modify the data.
Depending on the motor characteristics, however, it may take time for residual voltage to disappear (due to the
secondary thermal time constant of the motor). In such a case, the inverter starts the motor with the residual voltage
remaining, which will cause an error in the speed search and may result in occurrence of an inrush current or an
overvoltage alarm.
If it happens, increase the value of H46 data and remove the influence of residual voltage.
(If possible, it is recommended to set the value around two times as large as the factory default value allowing a
margin.)
• Be sure to auto-tune the inverter preceding the start of auto search for the idling motor speed.
• When the estimated speed exceeds the maximum frequency or the upper limit frequency, the inverter
disables auto search and starts running the motor with the maximum frequency or the upper limit
frequency, whichever is lower.
• During auto search, if an overcurrent or overvoltage trip occurs, the inverter restarts the suspended
auto search.
• If the inverter starts when the motor is idling with auto search disabled, an OC, etc. may occur, and the
inverter may be unable to start.
Note that auto search may not fully provide the performance depending on load conditions, motor
parameters, wiring length, and other external factors.
Motor speed/output
frequency
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