Specifications
DS - 4 Design Ver. 0002
Motor inertia
J
MOTOR
will be:
which are data that may be obtained from the characteristics in chapter SM.
Verify that in the characteristics table the rotor of the motor chosen in the 1st selection has
an inertia which meets the following condition:
J
MOTOR
equal to or greater than (
J
LOAD
/K
)
where
K
is a factor depending on the application destined for this motor.
The ideal will be to obtain a
J
MOTOR
equal to
J
LOAD
For a Positioning Axis, the typical value of
K
will be between 1 and 3
If this requisite is not met, a new motor must be selected which meets the conditions of the
1st selection and the 2nd one.
DS.1.3 THIRD MOTOR PRE-SELECTION
Calculation of the acceleration torque and time
The required acceleration torque is determined by the Total Inertia to be moved and the
needed acceleration. This acceleration is given by the Acceleration Time
t
AC
which is the time
required for the motor to reach the rated speed from resting position (0 rpm).
n
N
is the rated (nominal) motor speed
t
AC
is the time it takes the motor to go from "0" rpm to the rated speed.
From the same equation:
Calculation of the needed rms torque (
M
RMS
)
The third and last motor selection requires a new data, the RMS Torque:
where:
t
AC
is the acceleration time mentioned earlier.
t
P
is the tool positioning time.
t
C
is the cutting time in a typical machining cycle.
JJJ
MOTOR ROTOR BRAKE
=+
tJ
n
M
AC TOTAL
N
ACCELERATION
=
⋅
⋅
2
60
π
MJ
n
t
ACCELERATION TOTAL
N
AC
=
⋅
⋅
2
60
π
()()()
MMMM
t
T
MM
t
T
MMM
t
T
RMS F W AC
AC
FW
P
FWC
C
=++ ++ +++
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