Mitsubishi Electronics MDS-D-SVJ3 ユーザーズマニュアル

7 - 4

In addition to the continuous operation range, the servomotor has the short time operation range that can be 

used only in a short time such as acceleration/deceleration. This range is expressed by the maximum torque 

and the torque characteristics. The maximum torque or the torque characteristics differ according to each 

motor, so confirm the specifications in section "2-1 Servomotor".

The torque required for the servomotor’s acceleration/deceleration differs according to the CNC’s command 

pattern or the servo’s position control method.

Determine the required maximum motor torque from the following expression, and select the servomotor 

capacity.

(a) Selection with the maximum torque characteristics

In a low-speed rotation range (approximately less than half of the servomotor maximum speed), the 

linear acceleration/deceleration time constant "ta" that can be driven depends on the motor maximum 

torque. That can be approximated from the machine specifications using the expression (7-2).

  ••• (7-2) 

Using the approximate linear acceleration/deceleration time constant "ta" calculated above, confirm the 

torque characteristics of the high-speed rotation range in the CNC’s command pattern or the servo’s 

position control method.

N

: Motor reach speed

(r/min)

J

L

: Motor shaft conversion load inertia

(kg•cm

2

)

J

M

: Motor inertia

(kg•cm

2

)

η

: Drive system efficiency (Normally 0.8 to 0.95)

T

MAX

: Maximum motor torque

(N•m)

T

L

: Motor shaft conversion load (friction, unbalance) torque

(N•m)

ta =

(0.8

™T

MAX

-T

L

)

1.05

™10

-2

™(J

L

/

η+

J

M

)

™N

(ms)