9.2 Details of Function Codes
9-95
Chap. 9 FUNCTION CODES
H11 Deceleration Mode
H11 specifies the deceleration mode to be applied when a run command is turned OFF.
Data for H11 Function
0
Normal deceleration
The inverter decelerates and stops the motor according to deceleration
commands specified by H07 (Acceleration/deceleration pattern), F08
(Deceleration time 1), and E11 (Deceleration time 2).
1
Coast-to-stop
The inverter immediately shuts down its output, so the motor stops according
to the inertia of the motor and machine and their kinetic energy losses.
When reducing the reference frequency, the inverter decelerates the moto
according to the deceleration commands even if H11 = 1 (Coast-to-stop).
H12 Instantaneous Overcurrent Limiting (Mode selection)
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.
Data for H12 Function
0
Disable
An overcurrent trip occurs at the instantaneous overcurrent limiting level.
1
Enable
The current limiting operation is effective.
If any problem occurs 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.
The similar function is the current limiter specified by F43 and F44. The current
limiter (F43, F44) implements the current control by software, so an operation delay
occurs. When you have enabled the current limiter (F43, F44), also enable the
instantaneous overcurrent limiting with H12 to obtain a quick response current
limiting.
Depending on the load, extremely short acceleration time may activate the curren
limiting to suppress the increase of the inverter output frequency, causing hunting
(undesirable oscillation of the system) or activating the inverter overvoltage trip
(alarm
0
u
). When specifying the acceleration time, therefore, you need to take into
account machinery characteristics and moment of inertia of the load.
When the instantaneous overcurrent limiting is enabled, the motor output torque could drop.
For driving elevating machinery which could cause a serious problem with a drop of the motor
output torque, therefore, disable the instantaneous overcurrent limiting. Note that disabling it
will cause an overcurrent trip when a current exceeding the inverter protection level flows, so
secure the protective coordination using a mechanical brake.
An accident could occur.
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