Fagor QC-PDS, Hardware Manual

Page: 178 / 420

  
Selection criteria
5.
S
E
LECT
ING CRI
T
ERIA
Synchr
onous motor
selection
· 178 ·
198
Ref.2003
QC-PDS
HARDWARE
5.1.3 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.
The required acceleration is determined by the acceleration time t
AC
which is the time estimated for the motor to reach its rated speed from
zero rpm.
Solving the value of
t
AC
in the equation:
Calculation of the needed rms torque · M
rms
·
The third and last motor selection requires a new data, the RMS torque.
where:
The typical values for
t
AC
,
t
p
and
t
C
in a machine tool cycle are:
Calculation of the motor peak torque · M
peak
·
The required maximum torque is the sum of the friction, weight and
acceleration torque.
For a given acceleration time, we will need specific acceleration torque
and maximum torque. The motor must be able to provide a peak torque
equal to or greater than the calculated maximum torque.
Verify that the motor chosen in previous selections meets the following
condition:
n
N
Rated motor speed .
t
AC
The time it takes the motor to go from 0 rpm to the rated speed.
MACCELERATION JTOTAL
2

nN

60
tAC 
--------------------

=
tAC JTOTAL
2
 nN 
60
MACCELERATION 
--------------------------------------------------------

=
M
RPS
MF MW MAC + +
 
2 t
AC
T
------  MF MW +
 
2 tp
T
----  MF MW MC + +
 
2 t
C
T
---- 
+ +
=
t
AC
acceleration time.
t
p
tool positioning time.
t
c
cutting time in a machine cycle.
NOTE.
Peak torque equal to or greater than the calculated maximum
torque.
tC
T
------ 0.6 =
tP
T
----- 0.4 =
tAC
T
---------- 0

M
t
AC
t
P
t
C
t
AC
t
T
t
S
MMAX MF MW MAC + + =