5.3 Description of Function Codes 5.3.1 F codes (Fundamental functions)
If any problem could occur when the motor torque temporarily drops during current limiting processing, it is
necessary to cause an overcurrent trip (H12 = 0) and actuate a mechanical brake at the same time.
• Since the current limit operation with F43 and F44 is performed by software, it may cause a delay in
control. If you need a quick response current limiting, also enable the instantaneous overcurrent limiting
with H12.
• If an excessive load is applied when the current limiter operation level is set extremely low, the inverter
will rapidly lower its output frequency. This may cause an overvoltage trip or dangerous turnover of the
motor rotation due to undershooting. Depending on the load, extremely short acceleration time may
activate the current limiting to suppress the increase of the inverter output frequency, causing hunting
(undesirable oscillation of the system) or activating the inverter overvoltage trip. When specifying the
acceleration time, therefore, you need to take into account machinery characteristics and moment of
inertia of the load.
• The torque limiter and current limiter are very similar in function. If both are activated concurrently, they
may conflict with each other and cause hunting. Avoid concurrent activation of these limiters.
• Vector control with speed sensor itself contains the current control system, so it disables the current
limiter specified by F43 and F44, as well as automatically disabling the instantaneous overcurrent
limiting (specified by H12). Accordingly, the inverter causes an overcurrent trip when its output current
exceeds the instantaneous overcurrent limiting level.
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