
4. SELECTING A MOTOR
B–65142E/04
DESCRIPTIONS FOR THE α series
34
Following the procedure described below, calculate the torque required
for acceleration:
Assuming that the motor shaft operates ideally in the acceleration/
deceleration mode determined by the NC, calculate the acceleration.
Multiply the acceleration by the entire inertia (motor inertia + load
inertia). The product is the acceleration torque. The equation is given
below.
Time
Vm
ta
Ta
Vr
Vm
Speed
Command
Operation of
the motor
Torque
Speed
Speed variation Acceleration required to
achieve the speed
Ta + Vm 2p
1
ta
J
M
(1–e
–ks@ta
)
Ta : Acceleration torque
Vm : Motor speed in rapid traverse
ta : Acceleration time
J
M
: Motor inertia
J
L
: Load inertia
Vr : Point from which the acceleration torque starts to de-
crease
ks : Servo position loop gain
η : Machine tool efficiency
) Vm 2p
1
ta
J
L
(1–e
–ks@ta
) B h
Vr + Vm {1–
1
ta @ ks
(1–e
–ks@ta
)}
4.1.2
Calculating the
Acceleration Torque
Calculating acceleration
torque : Procedure 1
D In linear
acceleration/deceleration