Siemens SIMOTICS S-1FT7 User Manual

Technical data and characteristic curves
6.1 Explanations
S-1FT7 synchronous motors
138 Configuration Manual, 09/2018, A5E45099423B AA
2. Determine P2, the new point of intersection of the voltage limiting characteristic on the x
axis.
P2 corresponds to n
2
.
n
2
- calculate this as follows:
n
2
= n
1
• U
Mot new
/ U
Mot
n
2
/ rpm;
Converter output voltage U
Mot new
/ V
3. Determine P3.
At rated speed n
N
, draw a vertical line upwards to the voltage limiting characteristic.
P3 is the point of intersection.
4. From point P3, draw a horizontal line to the vertical torque axis.
At the point of intersection with the vertical torque axis, read-off the torque limit M
Limit
.
5. Calculate M
Limit, new
.
M
Limit, new
= (( U
Mot new
- U
IN
) / ( U
Mot
- U
IN
)) • M
Limit
M
Limit, new
/ Nm
Enter M
Limit, new
on the vertical torque axis.
6. Determine P4.
Draw a horizontal line from M
Limit, new
to the vertical line from n
N
.
The point of intersection of M
Limit, new
and n
N
is P4.
7. You obtain a new voltage limiting characteristic by drawing a straight line through points
P2 and P4.
You have determined the values to calculate the limit torque.
❒
Example for calculating the shift of the voltage limiting characteristic without field weakening
Procedure
e.g. motor 1FT7042-2AF71
n
N
= 3000 rpm
U
Mot new
= 290 V
k
E
= 87 V/1000 rpm
V
Mot
= 380 V
Determining the condition
U
iN
= k
E
∙ n
N
/1000
V
iN
= 87 ∙ 3000/1000
V
iN
= 261 V
V
iN
= 261 V < U
Mot new
= 290 V
The condition to shift the voltage limiting characteristic is fulfilled.

Siemens SIMOTICS S-1FT7 Specifications

General

Brand	Siemens
Model	SIMOTICS S-1FT7
Category	Engine
Language	English