Motor Operates With A Periodic Duty Cycle - Siemens SINAMICS S120 Configuration Manual

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
The torque to be generated by the motor comprises the frictional torque M
torque of the driven machine M
M = M
The accelerating torque M
M
B
J
motor+load
Δn
t
B
Figure 2-2
The M
A differentiation should be made depending on the period T and the thermal time constant
T
th
● T/T
● 0.1 ≤ T/T
● T/T
1PH4 Induction Motors
Configuration Manual, (APH4S), 08/2008, 6SN1197-0AD64-0BP1
+ M + M
friction load B
Acceleration torque in Nm referred to the motor shaft (on the motor side)
Total moment of inertia in kgm
Speed variation in rpm
Acceleration time, in s
Periodic duty cycle (example)
torque must be calculated from the load cycle:
rms
of the motor that is dependent on the shaft height:
≤ 0.1 (for a cycle duration of 2 to 4 min)
th
≤ 0.1 (for a cycle duration of 3 to 20 min)
th
> 0.5 (for a cycle duration of approx. 15 min)
th
2.3 Selecting and dimensioning induction motors
M in [Nm], P in [kW], n in [rpm]
and the accelerating torque M
load
is calculated as follows:
B
(on the motor side)
2
Configuring
, the load
friction
:
B
35