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  • EFD Switchmode Transformers

EFD Power Switchmode Transformers

(EFD Core Style)

Precision Inc has developed switchmode transformers utilizing industry standard configurations, such as materials and footprints.  These "standard" switchmode transformers are designed around a sizing factor number.  To determine which core style will work in your application we offer a Product Family Calculator to assist in the selection. 

If you prefer the EFD style core, the sizing factor Calculator is located below.

  • Low Profile
  • Low Leakage inductance designs
  • IEC-spacing compatible
  • Through hole and surface mount available
Mechanical Characteristics


EFD Mechnical Drawing

 * For standard product: Please select the quantity for each item you wish to order or receive a quote and click the 'Add To Quote' button below.
* For custom product: Please click 'Custom' button below. You will be directed to a page where you can add custom product information and attach prints.

Sizing Factor Calculator


EFD Sizing Factor

Once the core has been selected please contact our design engineers to assist with the transformer design and manufacturability issues such as; turns ratio, dielectric, wire breakout, pin termination, IEC margins, Rohs, REACH and other construction related requirements.

Sizing factor notes that apply to the chart above:

  1. Sizing constraints: Temperature rise is 40°C, the ambient temperature is 50°C and it does not include IEC Spacing.
  2. Increasing the operational frequency will reduce the sizing factor number and transformer size.
  3. Increasing the temperature rise allowed in the part will reduce sizing factor number and transformer size.
  4. Adding IEC dielectric requirements will increase the sizing factor number and transformer size.

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