Mitsubishi Electric MELDAS MDS-B-SVJ2 Series - Continuous Characteristics

Chapter 11 Selection
11-8
11-3-3 Continuous characteristics
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
(11-3).
Motor
torque
Motor
speed
0
0
T
3
T
2
t
1
t
2
t
3
t
4
t
0
T
1
Time
T
4
T
5
T
6
T
7
T
8
t
5
t
6
t
7
t
8
①②③④⑤⑥⑦⑧
Fig. 11-1 Continuous operation pattern
Trms =
T1
2
·t1 + T2
2
·t2 + T3
2
·t3 + T4
2
·t4 + T5
2
·t5 + T6
2
·t6 + T7
2
·t7 + T8
2
·t8
t0
.................. (11-3)
Select a motor so that the continuous effective load torque (Trms) is 80% or less of the motor rated
torque (Tra) (stall torque (Tst) in the HC, HAN Series).
Trms ≤ 0.8 · Tra (or 0.8 · Tst) .................................................. (11-4)
The amount of acceleration torque (Ta) shown in tables 11-6 and 11-7 is the torque to accelerate the
load inertia in a frictionless state. It can be calculated by the expression (11-5). (For linear
acceleration/deceleration)
Ta =
(J
L
+ J
M
) × N
95.5
×
ta
(N·m) .................................................. (11-5)
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 (msec)
In case of axis with imbalance torque. Select a motor so that a motor shaft conversion load torque (T
L)
(friction torque + unbalance torque) is 60% or less of the motor rated torque (Tra) (stall torque (Tst) in
the HC, HAN Series).
T
L ≤ 0.6 · Tra (or 0.6 · Tst) .................................................. (11-6)