Induction heater safety

[thaumatichthys]

Hi, just curious what would happen if someone touched the exposed coils of an induction heater?

I see that many designs have galvanic isolation between the input side and the coil, but what if someone happened to touch both sides? Especially on the ones where the coil has a high AC voltage across it?

Would it cause a shock? or not since the frequency is sort of high? or RF burns? or something else?

[petespaco]

It will be interesting to see what experts have to say on this set of questions about shocks from touching induction heater work? coils.
  I'd tend to say "it depends".  And then I could list a dozen or two scenarios with widely varying consequences.
 

[davekni]

It will be interesting to see what experts have to say on this set of questions about shocks from touching induction heater work?

Don't know that you will find any experts in shock hazards here.  I'm certainly not an expert in that area.  Always a bit difficult to say anything definitive given safety issues with being wrong.  So below is a bit of my limited understanding:
Induction heater frequencies are usually too high for nerves to respond.  Burns are much more likely consequence.  HOWEVER, that presumes that line voltage and DC bus voltage have no path to work coil.  Line frequency and DC are both shock hazards, especially line frequency.

[rikkitikkitavi]

I agree with Davekni,

If there is no galvanic insulation from power grid/line and output coil, there is a strong risk of electric chock as it is a low impedance path down to earth when you touch any part of the circuit. How dangerous that is depends on line frequency and voltage. More so in EU (50Hz 230V) than US (120ish 60Hz) fex but potentialy lethal in both cases.

If the output is insulated (fex with an transformer for power transfer) you need to make a closed loop over the circuit.

I have built one "smaller" Jacobs ladder with a 10kV/1kVA transformer operated with a 2kVA 230/230V insulating transformer, ie all parts are floating, including the high voltage. Still lethal of course if touching both terminals. 10kV kills.

I feel marginally safer.

[thaumatichthys]

I guess another thing would be that a lot of induction cookers tend to not have any smoothing on their inverter power supply, would that create enough low frequency component to be rather dangerous?

[davekni]

I guess another thing would be that a lot of induction cookers tend to not have any smoothing on their inverter power supply, would that create enough low frequency component to be rather dangerous?

Generally that "low frequency" shows up as amplitude modulation of the much higher induction frequency.  Amplitude modulation adds frequencies on either side of fundamental, but not any low frequency content (unless modulation frequency is close to fundamental frequency).

[rikkitikkitavi]

All parts on the induction cooker, table top och stove version are well insulated so there is no risk of electrical shock unless defective or wetted with water etc.

The reason the induction circuit is line frequency modulated is to save the cost of a bulky and expensive rectifier capacitor.

Also prone for breakdown as it would take a fair beating over time. Nowadays it is more and more common to use DC link caps in plastic insualation unless a electrolyte is really needed for the capacity. But not in induction stoves.

[petespaco]

Hi, just curious what would happen if someone touched the exposed coils of an induction heater?

What kind of induction heater are you asking about?