Y-cap in offline SMPS: Leakage prevents high voltage?

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eem2am

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Hello

The secondary ground of an offline SMPS can flot up to dangerously high voltages.

Is part of the reason for the Y-Cap, so that floating up to such a high voltage doesn't occur.................because the leakage current through the Y Cap will stop the secondary ground from floating up to such a high voltage?
 

The secondary ground of an offline SMPS can flot up to dangerously high voltages.
Click to expand...
Why? An dangerous in which sense?
Is part of the reason for the Y-Cap, so that floating up to such a high voltage doesn't occur.................because the leakage current through the Y Cap will stop the secondary ground from floating up to such a high voltage?
Click to expand...
Y-caps are provided for EMI supression. I dont expect, that you'll be able to measure a significant leakage with these high quality capacitors.

There's in fact a risk, that electrostatic voltages across the isolation boundary (and the Y-cap) causes a discharge at an unwanted place, e.g. damaging an opto coupler. Offline SMPS with profound design have probably a spark gap designed into the PCB, preferably as a milled air gap, to force the discharge to occur at this place.

A high-ohmic resistor in parallel to the Y-cap is another means to prevent static charges to build up.
 

supposing that such a high-ohmic resistor was not fitted in parallel with the y capacitor.....then would anyone touching the secondary side be likely to receive a shock?
 

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