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© ABB Group April 19, 2023 | Slide 1
Leak InductanceExplanation – your ref J1065
Pontus Sundqvist, Senior enginner 2012-08-22
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Content
General information about leakage inductance
Calculation of leakage inductance our ref 12Q1686204
© ABB Group April 19, 2023 | Slide 2
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Order Data Sheet
This is only applicable to coarse/fine connection
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IEC 60214-02 Tap-Changer Application Guide
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Normal Switching Conditions
Small L
Only one loop connected
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Normal Switching Conditions
Small L
Only one loop connected
Continued operation
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All loops in fine winding connected
Large L
All loops from both coarse and fine winding connected
Switching Conditions at Mid Point (Coarse/Fine)
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Critical breaking, going from coarse to fine.
Critical breaking, going from fine to coarse winding
Fine
Coarse
Continued operation at mid point
Switching Conditions at Mid Point (Coarse/Fine)
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Leak Inductance
The leak inductance can be :
Calculated with simple calculation (Only for radiell placed
windings)
Calculated with FEM program (ABB) (radiell or axiell placed
windings)
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Required Indata for FEM Calculations
I1
N1
t12 t2t1
I2
N2
DW2
DW1
DW3
I3
N3
I4
N4
t23
For accurate estimates of the reactance a FEM calculation must be done
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© ABB Group April 19, 2023 | Slide 11
Coarse- fine LV- fine Coarse- LV
FEM Calculation Axial Windings, part 1
HV
Coarse
Fine
LV
HV
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© ABB Group April 19, 2023 | Slide 12
LV- HV Coarse- HVFine - HV
FEM Calculation Axial Windings, part 2
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Further Calculations
© ABB Group April 19, 2023 | Slide 13
Coarse- fine LV- fine Coarse- LV LV- HV Coarse- HVFine - HV
Results from field calculation used in further calculation to establish severity at breaking
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© ABB Group April 19, 2023 | Slide 14
Determination of the recovery voltage
i2ci i1ci
ugci
Hg breaking Rf closing Rg breaking Hf closing
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Calculation of leakage inductance our ref 12Q1686204
© ABB Group April 19, 2023 | Slide 15
This window was drawn in ABB FEM program
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Window of one phase in FEM program
© ABB Group April 19, 2023 | Slide 16
Made following assumptions:
HV = 883 turns
Coarse 91 turns
Fine 84 turns.
Result:
Recovery voltage appox 6 kV more than 10 times above our limits.
6 kV equals approx 18mH
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Result
© ABB Group April 19, 2023 | Slide 17
Recovery voltage appox 6 kV more than 10 times above our limits.
6 kV equals approx 18mH.
In ordering data mentioned 2.15 mH compared to my calculated 18 mH.
18 mH is a normal value for axiell disposed windings (can be from approx 5 mH and higher)
For radiell disposed windings the leakage inductance normal is not higher than 5 mH.
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Why such big difference?
Some transformer manufactures use the formula mentioned in a book written ny a competitor to ABB which looks like this:
© ABB Group April 19, 2023 | Slide 18
This fomula is only valid radiell disposed windings not axiell.
This could explain the big difference, I don´t know.
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© ABB Group April 19, 2023 | Slide 19