Siemens 1FT7 Configuration Manual page 213

Figure 5-4
The load torque and the required start-up velocity define the gearbox output torque, the
output speed and therefore 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 the torque must
be reduced for S1 duty.
The required motor torque is calculated as follows:
M
M
mot
M
V
a
b
η
G
i
k
T
M
out
n
A
n
mot
R
ph
P
out
P
mot
π
1FT7 Synchronous Motors
Configuration Manual, (PFT7S) 01/2009, 6SN1197-0AD13-0BP2
Gear ratio
[W] = P [W] ∙ η = (π/30) ∙ M
mot G
M
M M
2 2
= ( + ) -
• i
Motor torque [Nm]
Calculated "torque loss" [Nm]
π/3 for 1FT7 motors supplied with sinusoidal current
Weighting factor for gearbox losses (without dimensions); b = 0.5
Gearbox efficiency
Gearbox ratio (i > 1)
Torque constant [Nm/A]
Gearbox output torque [Nm]
Output speed of gearbox [rpm]
Motor speed [RPM]
Resistance when hot of the motor phase [Ω]; R
headed "Technical data and characteristics")
Gearbox output power [W]
Motor power [W]
pi = 3.1416
[Nm] ∙ n [RPM] ∙ η
mot mot
n
( )
M
t = a • b • 1 -
60
Motor components
G
k
2
•
R
= 1.4 • R (see chapter
phw ph
5.4 Gearbox
213