
B-65262EN/03 SPECIFICATIONS FOR THE αiS/αi SERIES 3.SELECTING A MOTOR
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/ηηJ(J
t
1
60
2π
VT LM
1
ma +×××=
)
2
1(
1
2
t
t
VV
mr −×=
P
t
1
60
2 π
VAcc
1
ma
×××=
T
a
: Acceleration torque [N⋅m]
V
m
: Motor speed in rapid traverse [min
-1
]
t
1
: Acceleration time constant T1 [sec]
t
2
: Acceleration time constant T2 [sec]
J
M
: Motor inertia [kg⋅m
2
]
J
L
: Load inertia [kg⋅m
2
]
η : Machine tool efficiency
V
r
: Motor speed at which the acceleration torque starts to
decrease [min
-1
]
Acc
a
: Maximum workpiece acceleration [m/sec
-2
] [G]
P : Pitch [m/rev]
(Reference)
Minimizing t
1
and increasing t
2
by the same amount allows the
maximum workpiece acceleration (Acc
a
) to be increased and the
motor speed at which the acceleration torque starts to decrease (V
r
) to
be decreased. This allows the efficient use of the motor acceleration
torque.
If t
2
is too large, the positioning completion time (t
1
+ t
2
) tends to
increase.
Consequently, achieving a balance between t
1
and t
2
is effective in
obtaining required specifications of the machine.