An ideal transformer ignores magnetising current, winding resistance and voltage drop on load. It is the right first check for ratio and current, not a substitute for the nameplate.

Ratio and current

Fill both voltages, or one voltage and both turn counts. Primary current is optional.

Do not use this to design an isolation or safety transformer. Creepage, insulation and regulation are outside an ideal model.

These tools are quick guides for a ballpark figure. They are not certified design or test software, and a result on this page is not a design, a certificate, or a substitute for the current edition of BS 7671. Check the working and cross-reference it before you apply it to a real installation. Thanet Electrical Ltd does not accept liability for loss or cost arising from reliance on these figures, except where the law does not allow that liability to be excluded, including death or personal injury caused by negligence.

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