120Vac between Earth and DC ground

[harish1989]

Hi there,

In a induction stove board there is a AC voltage between DC ground and AC earth pin. Its showing 120VAC, and if I touch any microcontroller pin(120Vac w.r.t earth pin, in DC it is showing 5V w.r.t. ground pin ) I felt electric shock.

Please suggest what could be the reason?

And how to solve this leakage?

 

[betwixt]

I assume all parts of the induction stove are insulated so the user can't touch anything electrical. The most likely reason is either it feeds the AC lines to a bridge rectifier to produce 'floating' DC and it is the negative side of that being used as the device ground or, a transformer isolated SMPS is being used and the output side isn't connected to the earth pin.

If everything is out of reach of the user it isn't a danger.

Brian.

 

[KlausST]

Hi,

I have a laptop power supply that also shows about 100V of output against earth - high impedance.

Often on safety isolated power supplies (no EARTH GND connetion at all) the use HF capacitors
from [L to OUT_GND] as well as [N to OUT_GND].
This explains U_Mains/2 at output.

Usually the current is very limited, thus it is not dangerous at all. Still may feel it.

So the voltage may be expectable or it may be by fault. It depends on the circuit.

Klaus