Drive With Output Transformers - Siemens SINAMICS PERFECT HARMONY GH180 Function Manual

Advanced Operating Functions

8.25 Drive with Output Transformers

8.25 Drive with Output Transformers
A mismatch of drive and motor voltages may require the use of an output transformer to match
the voltages. Transformers are also used on long cable applications to reduce the cable losses by
first using a transformer to increase the output voltage on the drive, and then using a second
transformer to reduce the voltage at the motor. This reduces cable losses which are proportional
to the square of the current (not the voltage).
The following figure shows a typical setup with a step-up transformer to a long cable, connected
to a step-down transformer, which in turn attaches to the motor.
Drive
Figure 8-37 Output Transformer and Cable
The drive will compensate for the drive, cable, and transformer impedances when set up
correctly. In this case, the motor inductance is set up using the following parameters:
• Leakage inductance (1070): motor leakage inductance (L
• Stator resistance (1080): motor stator resistance (R
• Cable resistance (2940): resistance of the cable (len * R/len scaled by the turns ratio of T1)
• Cable inductance (2941): the total inductance of the cable + the inductance of the
secondary transformer T2 (both through the turns ratio of T1) + the inductance of T1
• Filter inductance (2920): this can be used for the transformer inductance of T1 as an
alternative to adding it to the cable impedance.
If an output transformer is used in conjunction with a cable (with or without an additional step-
down transformer), enter the impedances of the cable (and the extra transformer) after
applying the transformer turns ratio of T1 for the voltage loss (based on the current flowing
through them).
If an output transformer is used alone and connected directly to the motor, enter the transformer
inductance as either Filter inductance or Cable inductance, so that the drive can compensate for
voltage losses proportional to the output current. The following figure shows an example of such
a configuration.
336
L
T1
HV cable
L R
C
L L
T2
C
)
L
)
S
Operating Manual, A5E50491925A
R
L S
M
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