Configuring
2.3 Selecting and dimensioning induction motors
1PM6/1PM4 Hollow-Shaft Motors for Main Spindle Drives
Configuration Manual, PPMS, 04/2008, 6SN1197-0AD23-0BP0
29
2.3.5
Motor operates with a periodic duty cycle
The duty cycle determines how the drive is dimensioned. It is assumed that the speeds
during the duty cycle lie below the rated speed.
If the power is known, but the torques during the duty cycle are unknown, then the power
must be converted to a torque:
M = P ∙ 9550 / n
M in [Nm], P in [kW], n in [rpm]
The torque to be generated by the motor comprises the frictional torque M
friction
, the load
torque of the driven machine M
load
and the accelerating torque M
B
:
M = M
friction
+ M
load
+ M
B
The accelerating torque M
B
is calculated as follows:
0
ವ-ವ
0RWRUORDG
%
˭
-ವෙQ
0RWRUORDG
ವW
ෙQ
W
%
M
B
Acceleration torque in Nm referred to the motor shaft (on the motor side)
J
motor+load
Total moment of inertia in kgm
2
(on the motor side)
Δn
Speed variation in rpm
t
B
Acceleration time, in s
0 0
PD[F\FOH
0
7
0
W
W
0
0
W
W
W
W
0
Figure 2-2
Periodic duty cycle (example)
The M
rms
torque must be calculated from the load cycle:
0
UPV
0t෬W0t෬W
7
