Mitsubishi Electronics MDS-D-SPJ3 ユーザーズマニュアル

7 - 9

A typical operation pattern is assumed, and the motor's continuous effective load torque (Trms) is calculated 

from the motor shaft conversion and load torque. If numbers <1> to <8> in the following drawing were 

considered a one cycle operation pattern, the continuous effective load torque is obtained from the root 

mean square of the torque during each operation, as shown in the expression (7-9).

Fig. 1  Continuous operation pattern

  ••• (7-9)

Select a motor so that the continuous effective load torque Trms is 80% or less of the motor stall torque Tst.

Trms

0.8•Tst   ••• (7-10)

The amount of acceleration torque (Ta) shown in tables 7-3 and 7-4 is the torque to accelerate the load 

inertia in a frictionless state. It can be calculated by the expression (7-11). (For linear acceleration/

deceleration)

••• (7-11)

For an unbalance axis, select a motor so that the motor shaft conversion load torque (friction torque + 

unbalance torque) is 60% or less of the stall.

TL

0.6•Tst  ••• (7-12)

N

: Motor reach speed

(r/min)

J

L

: Motor shaft conversion load inertia

(kg•cm

2

)

J

M

: Motor inertia

(kg•cm

2

)

ta

: Linear acceleration/deceleration time constant

(ms)

η

: Drive system efficiency (Normally 0.8 to 0.95)

 

0

 

0

 

T3 

T2 

t1  t2  t3  t4  

t0  

T1 

T4 

T5 

T6 

T7 

T8 

t5  t6  t7  t8  

[1] 

[2] 

[3] 

[4] 

[5] 

[6] 

[7] 

[8] 

Motor
torque

Motor

speed

Time

Trms =

T1

2

·t

1+T2

2

·t2

+T3

2

·t3

+T4

2

·t4

+T5

2

·t5

+T6

2

·t6

+T7

2

·t7

+T8

2

·t8

t0

≦

T

a

 =

ta

1.05

™10

-2

™(J

L

/

η+

J

M

)

™N

(N

.

m)

≦