Electromagnetic study of a transformer

2015 Flux ConferenceElectromagnetic study of a transformer – Thursday 15 October

Presented by: Sébastien CORRECHER

Confidential Property of Schneider Electric

Losses in transformers

Losses in transformers can be divided in:

• No-load losses (measured with transformer energized at rated voltage and open-circuited)( g g p )

• Load losses (measured with transformer short-circuited and energized at reduced voltage, rated current)

Distribution transformers losses shall not exceed maximum values depending on rated power

• Examples:• Examples:

Rated power Rated voltage

Max no-load losses

Max load losses

100 kVA 15000 / 400 V 280 W 2050 W

400 kVA 20000 / 410 V 750 W 5500 W

1000 kVA 20000 / 400 V 1550 W 9000 W

Page 2Confidential Property of Schneider Electric |

• Trends are reducing the load and no-load losses

2500 kVA 10500 / 420 V 3600 W 23000 W

Losses in transformers

No-load losses depend on quality of magnetic steel and size of magnetic core easy to calculate before manufacturing

Load losses depend on conductor resistivity, conductor size, geometry of winding, quality of steel parts,… difficult to calculate before manufacturing

• DC losses in windings easy to calculate

• DC losses in connections easy to calculate

• Eddy losses in windings easy to calculate for wires, difficult to calculate for foils

• Eddy losses in connections difficult to calculate

• Eddy losses in mechanical steel parts difficult to calculate


Case of study

Dry-type, Cast Resin Transformer

• Rated power: 2500 kVA

• Rated voltages: 10500 / 420 VRated voltages: 10500 / 420 V

• LV winding technology: foils 1150×2,5 mm

• HV winding technology: strips 65×1,25 mm


Type of windings

LV winding technology: foils 1150×2,5 mmFoils 1150×2,5 mm, aluminium12 turns

HV winding technologystrips 65×1,25 mm, aluminium546 turns, 39 turns per pancake


Modeling performedOptional Subtitle Goes Here

Case 1 Case 2 Case 3

2D axisymmetric 2D axisymmetric 3D

Line conductors Surface solid conductorsNon-meshed coils

Volume solid conductors

DC losses in windings expected DC losses in windings expected DC losses in connections expected

Eddy losses in windings expected Eddy losses in windings expected Eddy losses in connections expected

Source of chart information, notes and other footnotes can be listed here.

Eddy losses in windings expected Eddy losses in windings expected Eddy losses in connections expected

Eddy losses in mechanical steel parts expected


Case 1: 2D axisymmetric, line conductorsOptional Subtitle Goes Here

One phase modeled

• Assuming no interaction between two adjacent coilsg j

Short-circuit test

• Current source feeding LV circuit, 3436 A

HV circ it short circ ited• HV circuit short-circuited

Two computations

• 0,5 Hz DC losses

• 50 Hz Eddy losses in windings

1591990 nodesDetail of mesh


Case 1: 2D axisymmetric, line conductors

Results Case 1 Measurements

DC l i LV i di 7068 WDC losses in LV winding 7068 W7426 W

DC losses in LV connections -

DC losses in HV winding 9119 W 9364 W

Eddy losses in LV winding 607 W

4613 WEddy losses in LV connections -

4613 WEddy losses in HV winding 645 W

Eddy losses in mechanical steel parts -


Case 2: 2D axisymmetric, surface conductorsOptional Subtitle Goes Here

One phase modeled

• Assuming no interaction between two adjacent coilsg j

Short-circuit test


HV circ it short circ ited• HV circuit short-circuited

Two computations

• 0,5 Hz DC losses

• 50 Hz Eddy losses in windings

2423885 nodesDetail of mesh


Case 2: 2D axisymmetric, surface conductors


DC l i LV i di 7045 WDC losses in LV winding 7045 W7426 W

DC losses in LV connections -



4613 WEddy losses in LV connections -

4613 WEddy losses in HV winding 1065 W

Eddy losses in mechanical steel parts -


Comparison between cases 1 and 2

Results Case 1 Case 2 Measurements

DC l i LV i di 7068 W 7045 WDC losses in LV winding 7068 W 7045 W7426 W

DC losses in LV connections - -

DC losses in HV winding 9119 W 9089 W 9364 W

Eddy losses in LV winding 607 W 712 W

4613 WEddy losses in LV connections - -

4613 WEddy losses in HV winding 645 W 1065 W

Eddy losses in mechanical steel parts - -


Case 3: 3D, surface conductorsOptional Subtitle Goes Here

Three phases modeled

• Non-meshed coils

• Steel parts modeled as massive conductors

• LV connections modeled as massive conductors

Short circuit testShort-circuit test


• HV circuit short-circuited

One computation

• 50 Hz Eddy losses in mechanical steel parts, DC+Eddy losses in LV connections


2627225 nodes

Case 3: 3D axisymmetric, surface conductors


DC l i LV i diDC losses in LV winding -7426 W

DC losses in LV connections767 W

Eddy losses in LV connections

4613 WEddy losses in mechanical steel parts 556 W

Eddy losses in LV winding -

Eddy losses in HV winding -

DC losses in HV winding - 9364 W


Compilation of cases 2 and 3

Results Case 2+3 Measurements

DC l i LV i di 7045 WDC losses in LV winding 7045 W 7500 W 7426 W


Eddy losses in LV connections

2590 W 4613 WEddy losses in mechanical steel parts 556 W


Eddy losses in HV winding 1065 W

DC losses in HV winding 9089 W 9089 W 9364 W

Load losses 19234 W 21403 W



Going further

Study of load losses in LV connections

• Improve modeling of contact foil / connections

Case 2+3 Expected

DC l i LV i di 7045 W 7045 Wp g

• Computation at 0 Hz to give DC losses

• Compare with computation at 50 Hz

DC losses in LV winding 7045 W 7045 W


740 W

Eddy losses in LV connections 1200 W

Modeling of mechanical structure with impedance surface

Eddy losses in mechanical steel parts 556 W 1200 W

Eddy losses in LV winding 712 W 712 W

Eddy losses in HV winding 1065 W 1065 W





Questions?Questions?


THANK YOUTHANK YOU.


Date post:	11-Jul-2016
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Electromagnetic study of a transformer

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