5.4 Details of Function Codes
5-117
Details of
Function Codes
F42 to F44
E codes
C codes
P codes
H codes
A codes
b codes
r codes
J codes
d codes
U codes
y codes
Chapter 5 Function Code
F43 and
F44
Current Limiter (Mode Selection and Level)
Related function codes: H12 (Instantaneous Overcurrent Limiting,
Mode selection)
When the output current of the inverter exceeds the level specified by the current limiter (F44), the inverter
automatically manages its output frequency to prevent a stall and limits the output current. The default
setting of the current limiter is 160%, 145% and 130% for HD-, MD- and LD-mode inverters, respectively.
(Once the HD, MD, or LD mode is selected by F80, the current limit for each mode is automatically
specified.) If overload current, 160% (145% or 130%) or more of the current limit level, flows instantaneously
so that an output frequency decrease problem arises due to the current limiter, consider increasing the
current limit level.
If F43 = 1, the current limiter is enabled only during constant speed operation. If F43 = 2, it is enabled during
both of acceleration and constant speed operation. Choose F43 = 1 if you need to run the inverter at full
capability during acceleration and to limit the output current during constant speed operation.
Mode selection (F43)
F43 selects the motor running state in which the current limiter becomes active.
Table 5.4-56
Running states that enable the current limiter
Data for F43
During acceleration During constant speed During deceleration
0 Disable Disable Disable
1 Disable Enable Disable
2 Enable Enable Disable
Level (F44)
F44 specifies the operation level at which the output current limiter becomes activated, in ratio to the inverter
rating.
- Data setting range: 20 to 200 (%) (in ratio to the inverter rating)
Instantaneous Overcurrent Limiting (Mode selection) (H12)
H12 specifies whether the inverter invokes the current limit processing or enters the overcurrent trip when its
output current exceeds the instantaneous overcurrent limiting level. Under the current limit processing, the
inverter immediately turns OFF its output gate to suppress the further current increase and continues to
control the output frequency.
Table 5.4-57
Data for H12 Function
0
Disable (An overcurrent trip occurs at the instantaneous overcurrent limiting level.)
1
Enable (Instantaneous current limiting enabled)
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.
y 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.
y 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 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.
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