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Creepage and clearance, in three answers

For transformers and inductors from 50 Hz to 10 MHz. Say what the part goes into, the voltage across the insulation and the kind of insulation, and you get the two minimum distances with the standard they come from.

01

What does it go into?

Application sector

The standard is picked for you.

02

What voltage does the insulation see?

V

The highest voltage that sits across this insulation in normal service. Above 30 kHz the high frequency rules of the standard apply, and distances grow.

03

What kind of insulation?

Insulation

Environment

Insulating material

If the datasheet of the bobbin or the board does not state a CTI, leave group IIIb. It is the conservative choice.

More conditions
V
V
m

Leave the peak empty for a sinusoidal or DC voltage. Fill it in for a switched waveform whose peak is higher than the RMS value suggests.

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After the number

The distance is fixed. The volume it costs is not.

Creepage can be folded into a bobbin flange, a barrier or a potted interface instead of being laid out flat, and that is most of the difference between a transformer that meets the standard and one that also fits. If the distances above do not fit your envelope, send us the specification and we will look at how to get them in.

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