ABB PVS800-57B, Руководство по оборудованию, Страница: 34 / 84

34 Planning the electrical installation
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Requirements for the transformer
These are the transformer requirements for any transformer connected to the AC main
supply of the inverter. This can mean a main transformer that connects the inverter to a
MV (or LV) network or an external auxiliary power transformer that is tapped to an AC
supply (possible with G429).
•
Suitable for the network and inverter AC voltage, current and power
•
Suitable for use with IGBT inverters
•
Degree of protection, temperature limits and lifetime are appropriate for the
environment
•
Equipped with a static grounded screen between the high and low voltage windings
•
Voltage withstand level of the inverter-side winding is at least 2.0 kV against ground.
A typical voltage waveform against ground:
•
If several inverters are connected to the same transformer:
•
Each inverter requires a separate galvanically isolated winding.
•
The impedance between the inverter windings must be more than 10%.
•
Voltage rise time withstand level (d u /d t ) of the inverter-side winding is at least 1000 V
per microsecond against ground.
•
Recommended rated short-circuit impedance (X
k
) for each inverter is 4...8%
•
Withstands current DC components of at least 0.5% of the nominal rated current
preferably without using an air gap
•
Withstands the worst case of 3% total harmonic distortion generated by the inverter.
ABB recommends dimensioning the transformer for at least 5% total harmonic distortion to
withstand possible outside interference from the network.
ABB recommends that the transformer is equipped with an off-load tap changer for voltage
regulation on the high-voltage side of the winding with two 2.5% step points to the plus and
minus directions.
1000
800
600
400
200
0
U[V]
t[ms]
-200
-400
-600
-800
-1000
5
10 15
20 25
30