Transformer Bobbins: Core Fit, Winding Space and Pins

JHCOILS lists transformer bobbin references for EE, PQ, POT, EFD and ETD core families. Select by the dimensioned drawing, winding window and terminal layout; the family name alone is not enough to confirm fit.

High frequency transformer bobbin

What to Check on a Transformer Bobbin Drawing

Check the core opening, usable winding width, flange dimensions, overall height, pin pitch and pin numbering. Show the PCB footprint and lead exits so the bobbin can be reviewed in the assembled transformer rather than as an isolated plastic part.

Material Grade and Mounting Configuration

Bobbin drawings may specify thermoplastics such as PA/nylon, PET or PBT, or a thermoset such as phenolic. Confirm the exact resin grade, reinforcement, temperature data and molding specification for the selected part.

A material family name does not establish a flame rating or an insulation-system approval. Request the relevant grade document, rated thickness and applicable test evidence when these are purchasing requirements. Also specify horizontal or vertical mounting, number of winding chambers and pin arrangement.

Transformer Bobbin Reference Size Charts

Compare Dimensions, Pins and Matching Core Size

EE Series Transformer Bobbins

For an EE bobbin, check the center-leg opening, flange spacing and pin layout against the selected core set and PCB. Use the chart as a starting point and request the current drawing for the chosen size.

ProductsDatasheetProduct CodeDescriptionAsk for sample
A1 Wireless power Transmission coil
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EE01E12.5 Vertical 5+5 Transformer BOBBINContact Us
A5 Transmission coil with magnetic
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EE02E105.55 Horizontal 4+4 Ferrite BOBBINContact Us
A10 wireless Transmission coil with magnetic
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EE03E13610 Vertical 5+5 BOBBINContact Us
A10 wireless Transmission coil with magnetic
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EE04E25106 Vertical 3+3 BOBBINContact Us
A11 power charging coils single layer tx coil
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EE05E331413 Vertical 17+17 BOBBINContact Us
A12 power charging coils single layer tx coil
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EE06E331413 Vertical 18+18 Transformer BOBBINContact Us

PQ Series Transformer Bobbins

For a PQ assembly, compare the core opening and winding window as well as the terminal footprint. Confirm that the bobbin and core share the same dimensional reference.

ProductsDatasheetProduct CodeDescriptionAsk for sample
PQ transformer bobbin
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PQ01PQ2016 Vertical 6+8 transformer bobbinContact Us
PQ transformer bobbin
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PQ02PQ2020 Vertical 6+8 transformer bobbinContact Us
PQ transformer bobbin
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PQ03PQ3220 Vertical 6+6 transformer bobbinContact Us
PQ transformer bobbin
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PQ04PQ3225 Vertical 6+6 transformer bobbinContact Us
PQ transformer bobbin
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PQ05PQ3535 Vertical 6+6 transformer bobbinContact Us
PQ transformer bobbin
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PQ06PQ4040 Vertical 6+6 transformer bobbinContact Us
PQ transformer bobbin
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PQ07PQ5050 Vertical 6+6 transformer bobbinContact Us

POT Series Transformer Bobbins

For a POT core, verify the bobbin fits inside the complete core set and that the lead exits clear the core and mounting hardware. Specify the winding chambers and pin orientation.

ProductsDatasheetProduct CodeDescriptionAsk for sample
POT transformer bobbin
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POT01POT40 Vertical 6+6 BOBBINContact Us
POT transformer bobbin
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POT02POT3019 Vertical 5+5 BOBBINContact Us
POT transformer bobbin
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POT03POT3314 Vertical 5+5 BOBBINContact Us

EFD Series Transformer Bobbins

For an EFD bobbin, check assembled height, insulation distances, winding build and pin accessibility. Resin grade, flame rating and dielectric test requirements must be confirmed for the exact part; the chart does not establish a universal voltage rating.

ProductsDatasheetProduct CodeDescriptionAsk for sample
EFD transformer bobbin
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EFD01EFD157.54.6 Horizontal 4+5 BOBBINContact Us
EFD transformer bobbin
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EFDT02EFD2512.59 Horizontal 5+5 BOBBINContact Us
EFD transformer bobbin
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EFD03EFD20106.6 Horizontal 5+5 BOBBINContact Us
EFD transformer bobbin
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EFD04EFD25259 Horizontal 5+5 BOBBIN
EFD transformer bobbin
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EFD05EFD30159 Horizontal 6+6 BOBBIN

ETD Series Transformer Bobbins

For an ETD bobbin, provide winding build, terminal current requirements, mounting layout and insulation boundaries. Suitability for an industrial, automotive or power-conversion product requires review of the complete transformer specification.

ProductsDatasheetProduct CodeDescriptionAsk for sample
ETD transformer bobbin
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ETD01ETD291510 Vertical 7+7 BOBBINContact Us
ETD transformer bobbin
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ETD02ETD341711 Horizontal 7+7 BOBBINContact Us
ETD transformer bobbin
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ETD03ETD492516 Horizontal 10+10 BOBBINContact Us
ETD transformer bobbin
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ETD04ETD542719 Horizontal 11+11 BOBBINContact Us
ETD transformer bobbin
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ETD05ETD593122 Horizontal 12+12 BOBBINContact Us
ETD transformer bobbin
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ETD06ETD593122 Horizontal 13+13 PET BOBBINContact Us

Insulation and Winding Requirements

Mark the primary and secondary winding positions, barriers, margins, creepage and clearance requirements on the drawing. State the insulation system and test procedure expected for the finished transformer. Bobbin geometry and resin documentation are inputs to that review, not a substitute for assembly validation.

transformer core bobbin

Order the Bobbin with the Matching Assembly Data

Send the bobbin code, dimensioned drawing, matching ferrite core reference and pin schedule. If the scope includes winding and lead preparation, review bobbin-wound coil manufacturing and specify the acceptance requirements for the finished component.

Ferrite Core Test Equipment

Request a Bobbin Drawing or Sample Review

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