
3.SELECTING A MOTOR SPECIFICATIONS FOR THE αiS/αi SERIES B-65262EN/03
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3.2.4.2 Calculating the torque required by the motor shaft in
acceleration
To obtain the torque required by the motor shaft (T), add the constant
load torque (T
m
) to the acceleration torque (T
a
).
ma TTT +=
T : Torque required by the motor axis
T
a
: Acceleration torque
T
m
: Constant load torque
[Example of calculation for condition 4-2] Acceleration torque
When T
m
is 3.0 N⋅m as calculated in example of calculation <1> and
T
a
is 74.9 N⋅m as calculated in example of calculation <3>-1, the
acceleration torque (T) is calculated as follows:
T = 74.9[N⋅m] + 3.0[N⋅m] = 77.9[N⋅m]
The speed when the maximum torque is required (V
r
) is 2050 [min
-1
].
The speed-torque characteristics of the α22/4000is, given below,
show that the point of 77.9 [N⋅m]/2050 [min
-1
] is beyond the
intermittent operating zone of the α22/4000is (the torque is
insufficient).
77.9[N⋅m]
/ 2050[min
-1
]
Speed - torque characteristics
0
10
20
30
40
50
60
70
80
0 1000 2000 3000 4000
Speed (min
-1
)
Torque (Nm)
Speed - torque characteristics for α
αα
α22/4000iS
If it is impossible to change the operation specifications of the shaft
(such as to increase the acceleration time), a larger motor must be
selected.
Select the α30/4000is (motor inertia (J
M
) = 0.0076 [kgm
2
], 1.9 times
load inertia ratio) and calculate the acceleration torque again.
T
a
=83.2[N⋅m]=849[kgf⋅cm]
V
r
=1863[min
-1
]
T=83.2[N⋅m]+3.0[N⋅m] = 86.2[N⋅m]