Toshiba TOSVERT VF-AS1 Manual page 3

4. Adjustment
4-1. How to adjust the speed control gain
This section explains how to adjust the speed control gain-related parameters (f458, f460, f461,
f462).
By default, the response is set at approximately 5Hz based on the assumption that the inertia of the load is
almost the same as the inertia of the motor (CPU versions of VF-AS1 is 124 and later). Therefore, if the inertia
of the machine (inertia of the motor shaft) is reduced by means of gears, a belt, etc., the gain does not need to
be adjusted in most cases.
If motor hunting occurs, or the motor hums, or gears squeak (if a gear motor is used) when the machine is
operated under load or no-load conditions, then adjust this gain.
4-1-1. If the inertia of the load is unknown or there is no waveform measuring device available
(1) Adjusting the setting of f461 (speed loop stability factor)
The figures below show the relationship between the setting of f461 and step response. Increasing
the setting of f461 eliminates the occurrence of overshoots and makes operation stable. However,
it reduces the response.
If you do not have a step response measuring device, follow these steps to adjust the setting of
.
Operate the machine under no-load at low, intermediate and high speeds to determine whether motor
hunting occurs, the motor hums or gears squeak (if a gear motor is used). If an unusual event has
occurred, increase the set value of f461 until the unusual event disappears. Then, adjust the
setting of f460.
Increase in
response
(2) Adjusting the setting of f460 (speed loop proportional gain)
The relationship between the setting of f460 and step response is shown on the next page.
The adjustment of f461 in (1) above stabilizes the motor and allows it to run without hunting. If the
response needs to be increased in such a situation, follow these steps to adjust the settings of
f460 and f461.
The response can be increased by increasing the set value of f460, as described on the next page.
To increase the response while keeping the motor in the state in (1) where an overshoot does not
occur, parameter f461 also needs to be adjusted according to the following formulas. This
adjustment makes high-speed and stable operation possible.
Speed
f461 set low
f461 set high
Reduction in
response
f461=100
Output frequency
Time
f461=200 f461=500
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