Capacity Selection - Mitsubishi Electric MELSERVO MR-J2-A Product Specifications And Installation Manual

11.SELECTION

11-5 Capacity selection

As a first step, temporarily select the servo motor capacity by calculating the load conditions. Next,
determine the command pattern, calculate required torques according to the following equations,
and confirm that the servo motor of the initially selected capacity may be used for operation.
(1) Initial selection of servo motor capacity
After calculating the load torque (T
will satisfy the following two relationships:
Servo motor's rated torque > T
Servo motor J > J
M
Find the acceleration and deceleration torques and continuous effective load torque as described
in (2) to make a final selection. For high-duty positioning, the J
possible. If positioning is infrequent as in line control, the J
the above conditions.
(2) Acceleration and deceleration torques
The following equations are used to calculate the acceleration and deceleration torques in the
following operation pattern:
Acceleration
torque
Deceleration
torque
• Acceleration torque T
• Deceleration torque T
(3) Torques required for operation
Torques required for the servo motor are the highest during acceleration. If any of the torques
obtained with Equations 11-9 to 11-13 exceeds the maximum servo motor torque, the servo
motor speed cannot be increased as commanded. Confirm that the calculated value is lower
than the servo motor's maximum torque. Since a friction load is normally applied during
deceleration, only the acceleration torque needs to be considered.
) and load inertia moment (J
L
L
/m
L
m=3
m=5
m= permissible load inertia moment : Low duty (less than 60 times/min.)
Command
Nofo
f
0
[r/min] [pps]
Tpsa
Ta
0
Td
(J +J ) • N
L M o
= •
a
4
9.55 x 10
(J +J ) • N
o
L M
•
=
b 4
9.55 x 10
: High duty (more than 100 times/min.)
Settling time 40ms or less
: Middle duty (60 to 100 times/min.)
Settling time 100ms or less
Settling time more than 100ms
value may be slightly larger than in
L
Servo motor
speed
Tpsd
1
........................................................................ (11-9)
Tpsa
1
...................................................................... (11-10)
Tpsd
11– 6
), select a servo motor which
L
value should be as small as
L
Time
Time