8 ms·

The DC side is fully isolated except through a capacitor that is there to reduce EMI interference and is specifically built to "fail safe", except for the cheap

by moqmar 1y ago

The DC side is fully isolated except through a capacitor that is there to reduce EMI interference and is specifically built to "fail safe", except for the cheapest no-name imported power supplies. (https://www.pcbaaa.com/y1-capacitors-function-application-and-comparison/ https://www.pcbaaa.com/y1-capacitors-function-application-an...)

MadnessASAP 1y ago
A Y capacitor prevents the neutral from shorting to ground, in this case Apple has cleverly avoided the issue by not having a ground whatsoever. I am however curious about your design for a galvanically isolated AC-DC power supply.
- grues-dinner 1y ago
  That's not what the Y capacitor is doing here. All Y means is "high voltage withstand, will fail open, and we have receipts". Here, it's not line-to-ground, but primary-to-secondary. Isolated ACDC converters are very common these days. Companies like Traco will sell you modules: https://www.tracopower.com/isolated-power-supplies https://www.tracopower.com/isolated-power-supplies
  - MadnessASAP 1y ago
    You'd use X for L to L/N, Y is for N to Ground. Those isolated power supplies are definitley grounded, definitely not what Apple is using, and will probably shut themselves off if they lose their ground connection (or at least signal a fault to the operator)
    - grues-dinner 1y ago
      Unlikely, since you can quite happily buy two-prong power supplies. And most packaged modules don't even have ground connections, e.g. https://www.tracopower.com/sites/default/files/products/datasheets/tmlm_datasheet.pdf https://www.tracopower.com/sites/default/files/products/data... You're also confusing the Y designation, which relates to the capacitor properties, to the application. Not all Y capacitors are used for line-to-ground applications. However any application where a failure to a closed state would result in a shock hazard must use Y-rated capacitors.

by moqmar 1y ago

MadnessASAP 1y ago

A Y capacitor prevents the neutral from shorting to ground, in this case Apple has cleverly avoided the issue by not having a ground whatsoever. I am however curious about your design for a galvanically isolated AC-DC power supply.

grues-dinner 1y ago
That's not what the Y capacitor is doing here. All Y means is "high voltage withstand, will fail open, and we have receipts". Here, it's not line-to-ground, but primary-to-secondary. Isolated ACDC converters are very common these days. Companies like Traco will sell you modules: https://www.tracopower.com/isolated-power-supplies https://www.tracopower.com/isolated-power-supplies
- MadnessASAP 1y ago
  You'd use X for L to L/N, Y is for N to Ground. Those isolated power supplies are definitley grounded, definitely not what Apple is using, and will probably shut themselves off if they lose their ground connection (or at least signal a fault to the operator)
  - grues-dinner 1y ago
    Unlikely, since you can quite happily buy two-prong power supplies. And most packaged modules don't even have ground connections, e.g. https://www.tracopower.com/sites/default/files/products/datasheets/tmlm_datasheet.pdf https://www.tracopower.com/sites/default/files/products/data... You're also confusing the Y designation, which relates to the capacitor properties, to the application. Not all Y capacitors are used for line-to-ground applications. However any application where a failure to a closed state would result in a shock hazard must use Y-rated capacitors.