4-1-2. If the inertia of the load is unknown, but there is a waveform measuring device such as an oscilloscope
(1) Connect the probes of the measuring device to the analog monitor output terminals (FM terminal-CC
terminal) of your inverter. Then, change the FM terminal output setting to 6: speed feedback (real
In addition, set f462 (moment of inertia of load 1) to 0 and remove the acceleration/deceleration
(2) Reduce the acceleration time to a minimum within the bounds of not causing an overcurrent stall (c
(3) Set the operation mode selection parameter (cmod) and the speed command selection parameter
(cmod) so that they can be adjusted with the operation panel. (cmod="1" cmod="5")
(4) Set the speed command at 10Hz or so with the
(5) Set the preset speed command (sr1) to 13 to 15Hz and enter the preset speed command (turn on
the S1 terminal) when constant-speed operation is performed at the frequency set in (4). Now, you
can observe step response at frequencies of 10Hz and above. You can start observing the step
response the moment the inverter starts, but in that case, it is difficult to observe the waveform
because it is affected by motor excitation control at startup, and therefore it is recommendable to
start observing step response after operation has entered the above-mentioned constant-speed
(6) Adjust the settings of parameters f460 and f461, observing the step response waveform (the
steps to be followed to adjust these parameters are the same as those described in section 4-1-1).
First, increase the set value of f461 to eliminate overshoots. Then, increase the set value of
f460 reducing the set value of f461 at the same rate, in order to increase the response to the
desired level without causing an overshoot. Finally, return the setting of f462 to 35 (default
setting) to finish the adjustments.
4-1-3. If both the inertia of the load and the inertia of the motor itself are known
The table below shows examples of the settings of parameters related to the inertia of a load and the
inertia of a motor.
The formula in the bottom row is used to calculate the setting of f460.
If necessary, make the adjustments described in 4-1-1 or 4-1-2, using the values in this table as a guide.
Inertia of load/inertia of
To increase the speed of response of a machine with a high-inertia load, high torque, more specifically a
large electric current is required for the motor. Therefore, if you are using a machine with a high-inertia
load for which high-speed responsivity is not required, you are recommended to reduce the speed of
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key on the operation panel and start operation.