Mitsubishi Electric MELSERVO-J2S Series Transition Handbook page 486

[Appendix 1] Summary of MR-J4_B_-RJ020 + MR-J4-T20
(7) Changing the load to motor inertia ratio
When the moment of inertia of a servo motor is changed due to replacement of the MR-J2S series servo
motor (HC-_FS/HA-_FS series) with the MR-J4 series servo motor (HG series), the load to motor inertia
ratio needs to be changed to a proper value.
Change the load to motor inertia ratio with one of the following methods 1) and 2). Check that operation
can be performed normally after the setting with one of the methods. If a problem such as vibration
occurs, manually set the load to motor inertia ratio 3).
1) Setting by auto tuning
After replacing servo motors, perform auto tuning in the mode in which the load to motor inertia ratio is
estimated by setting [Pr. 8 Auto tuning]. For details, refer to Section 6.2 "Auto tuning" of "Conversion
Unit for SSCNET of MR-J2S-B Compatible AC Servo MR-J4-_B_-RJ020/MR-J4-DU_B_-RJ020/MR-
CR55K_/MR-J4-T20 SERVO AMPLIFIER INSTRUCTION MANUAL". When using the gain switching
function, change [Pr. 52 Load to motor inertia ratio 2] as necessary.
2) Setting with the parameter for the load to motor inertia ratio (software version A6 or later)
When auto tuning is not performed or only the load to motor inertia ratio is changed, the load to motor
inertia ratio can be changed by setting the parameter for the load to motor inertia ratio. To set the load
to motor inertia ratio, set "_ _ _1" in [Pr. 59 Option function B] and set the ratio calculated by dividing the
moment of inertia of the servo motor before replacement by the moment of inertia of the servo motor
after replacement in [Pr. 35 Load to motor inertia ratio] in percentage.
Example) When a HC-KFS053 motor is replaced with a HG-KR053 motor, set "_ _ _1" in [Pr. 59 Option
function B] and 118 in [Pr. 35 Load to motor inertia ratio].
Moment

Pr.35
Moment
Moment

Moment
0.053

0.0450
* The load to motor inertia ratio function is enabled when the value of [Pr. 8 Auto tuning] is 2, 3, or 4.
The load to motor inertia ratio function is disabled when the value of [Pr. 8 Auto tuning] is 0 or 1. In
this case, the ratio is not applied.
* For the moment of inertia of a servo motor, refer to the instruction manual of the servo motor used or
Section 2.5 "Comparison of Moment of Inertia" in Part 8.
* The load to motor inertia ratio function changes the internal value of the load to motor inertia ratio
using the ratio calculated by dividing the moment of inertia of the servo motor before replacement by
the moment of inertia of the servo motor after replacement. The characteristics of the servo motor
after replacement may not be the same as those of the servo motor before replacement only by
changing the load to motor inertia ratio. If a problem occurs, manually set the load to motor inertia
ratio 3).
* This function is not supported by geared servo motor.
* After GD2 ([Pr. 12]) is estimated by auto tuning, disable the load to motor inertia ratio function by
setting [Pr. 59 Option function B] to "_ _ _0" and [Pr. 35 Load to motor inertia ratio] to 0.
POINT
The software version A6 or later supports the "load to motor inertia ratio" function.
When the "load to motor inertia ratio" function is enabled, always check the setting
value of [Pr. 35].
If a proper value has not been set in [Pr. 35], the servo motor may operate
unexpectedly.
of inertia before replacemen
of inertia after replacemen
of inertia for HC - KFS053
of inertia for HG - KR053
 
4
10
 
100 118
 
4
10
t

100[%]
t

100
Appendix 1-23