Siemens SIMOTICS S-1FT7 Configuration Manual page 120

Configuration
5.3 Dimensioning the gearbox
NOTICE
Gearbox failures as a result of superimposed oscillations
Switching cycles can also be superimposed oscillations. The safety factor (f
adequately dimensioned. This can result in gearbox failures.
• Optimize the overall system so that the superimposed oscillations are minimized.
1
2
Figure 5-7
The load torque and required starting speed define the gearbox output torque and the output
speed - and in turn, the output power.
The required drive power is calculated from this:
P
Out
Dimensioning for S1 duty
The gearbox itself generates heat due to friction and acts as a thermal barrier preventing
heat from being dissipated through the motor flange. This is the reason that you must reduce
the torque for S1 duty.
The required motor torque is calculated as follows:
M
Mot
M
/ Nm
V
a
b
η
G
i
k
/ Nm/A
T
M
Out
n
Out
n
Mot
R
Phw
P
Out
P
Mot
π
118
Motor
Gearbox
Configuring the gearbox
P η π/
/W = /W ∙ = (
Mot G
/ Nm Motor torque
Theoretical "Torque loss"
π/3 for 1FT7/1FK7 motors supplied with sinusoidal current
Weighting factor for gearbox losses (without dimensions); b = 0.5
Gearbox efficiency
Gearbox ratio (i > 1)
Torque constant
/ Nm Gearbox output torque
/ rpm Gearbox output speed
/ rpm Motor speed
/ Ω Motor phase resistance when warm; R
data and characteristics")
/ W Gearbox output power
/ W Motor power
pi = 3.1416
∙ M n
30) /Nm ∙ /rpm ∙
Mot Mot
η
G
= 1.4 • R (see Chapter "Technical
Phw Ph
S-1FT7 synchronous motors
Configuration Manual, 09/2018, A5E45099423B AA
) is then not
2