Transformadores

more than you expect

Cookbook
for do-it-yourself transformer design

Content

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more than you expect

Introduction Transformer Design Step-by-step to flyback converter design 1st step: Definition of the turns ratio and the duty cycle 2nd step: Definition of inductance 3rd step: Selection of the core 4th step: Calculating primary turns 5th step: Defining the wire cross sectionTransformer Construction Step-by-step-construction Glossary Speedy Design Service Product Overview more than you expect

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Introduction
The Speedy Design Kits are made for engineers to wind first transformer samples to test and optimize their Switch Mode Power Supply (SMPS). The material in the Design Kits is standard material. Thusthere will be no material shortage in mass production. The material is suitable for the power ranges: • 5-15 W (Low Power Kit) Order Code: 750 102 • 15-30 W (Medium Power Kit) Order Code: 750 101 • 5-30 W (All inclusive Design Rack) Only available on request This “Cookbook” in hand shows you examples how to design and wind a transformer. For engineers which want to concentrate on there circuit andnot design their own transformer we also offer our SPEEDY DESIGN SERVICE. For the SPEEDY DESIGN SERVICE please see page 20. SPEEDY DESIGN SERVICE is the world´s fastest sample service for customized transformers. The service offers the unique possibility to get samples designed to your requirements and delivered when you need them – guaranteed! Order our SPEEDY DESIGN SERVICE when requestingsamples and samples will be shipped within the selected time.

PLEASE NOTE: Althought great care has been taken to provide accurate and current information, neither the authors nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage, or liability directly or indirectly caused or alleyed to be caused by this book. All appropriate material is only validfor low power applications. For applications with 60 VDC / 48 VAC or more, please refer to relating safety regulations.

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more than you expect

Content of the Speedy Design Kits

Speedy Design Kit Low Power 5-15 W Bobbins ER11, ER14.5, EFD15, EE13

Speedy Design Kit Medium Power 15-30 W EFD20, EE16, EE20, EE25

Speedy Design Rack (only available on request) ER11, ER14.5, EFD15,EFD20, EE13, EE16, EE20, EE25 0.1 mm (AWG38) 0.15 mm (AWG34) 0.2 mm (AWG32) 0.28 mm (AWG29) 0.3 mm (AWG28) 0.35 mm (AWG27) 0.4 mm (AWG26) 0.5 mm (AWG24) Suitable for all bobbins in Rack ER11, ER14.5 (different airgaps) EFD15, EFD20 (different airgaps) EE16, EE20, EE25 (no gap) Mylar 0.05 mm, 0.1 mm, 0.15 mm, 0.19 mm Design Guide „Abc of transformers“ and Software for Flyback Design„WE-FLEX-DESIGNER“ on request

Wires (ø)

0.1 mm (AWG38) 0.15 mm (AWG34) 0.2 mm (AWG32) 0.28 mm (AWG29) 0.3 mm (AWG28)

0.1 mm (AWG38) 0.3 mm (AWG28) 0.35 mm (AWG27) 0.4 mm (AWG26) 0.5 mm (AWG24)

Wrapper tape Cores

Suitable for all bobbins in Kit ER11, ER14.5 (different airgaps) EFD15 (different airgaps) EE13 (no gap) Mylar 0.05 mm, 0.1 mm, 0.15 mm, 0.19 mm -

Suitable for all bobbins in Kit EFD20(different airgaps) EE16, EE20, EE25 (no gap) Mylar 0.05 mm, 0.1 mm, 0.15 mm, 0.19 mm -

Gapping Material

Extras Order Code

750 102

750 101

Tab. 1: Contents of the Speedy Design Kits

05

Transformer Design
The following example gives you an idea how to design a transformer for a flyback converter. Fig. 1 is an overview on how to proceed. As you see from this flow chart transformerdesign is a highly iterative process. Further transformer designs for forward converters and push pull converters are integrated in Würth Elektronik´s Application and Design Guide “Abc of Transformers”.

Compile specifications

Define duty cycle (max.) and turns ration

Calculate inductance

Decide on core

Define the number of turns and calculate core losses no Core loss ok? yes...