A regular electric stove using resistive elements will see a performance drop-off from the 240v rating when operated on 208v. Does this also hold true for an induction cooktop ? Or do current induction stoves use high frequency switching to eliminate this drawback, similar to how a "universal" ac adapter can power a laptop regardless of 110 vs 220v ?
Induction cooktop performance 208v vs 240v
- Thread starter Nechaken
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That's a great question. I suspect the latter.
Thank you for that. Interesting that Viking lists two different outputs. I see some other manufacturers (Bosch, Samsung) just list a single rating. But even on those, it would have to be derated at 208V given the given listed current draw. (IE the 30A @ 240 would become 34A @ 208V for this one):
https://media3.bosch-home.com/Documents/20011272_NITP060SUC Spec Sheet.pdf
https://media3.bosch-home.com/Documents/20011272_NITP060SUC Spec Sheet.pdf
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Although the description of the working mechanism of an induction cooktop is often popularly described as based on eddy currents, this by itself does not clearly point out the operating principles of their use.
1. Eddy currents result from a changing magnetic field in a conducting material with bulk resistance. For a given external magnetic field, a ferrous metal cooking vessel will have higher internal magnetic field, hence stronger eddy currents. The changing magnetic field tries to produce a compensating magnetic field caused by the eddy currents. This mechanism acts as a current source in the material, not a voltage source, for low resistances.
2. The heating due to the eddy currents will increase as the effective resistance of the pot surface increases. One way to do this is to concentrate the current in a thinner layer of the ferrous metal. One way to do this and still have a sturdy pot bottom is to make use of skin effect. To get a useful skin effect contribution, frequencies higher than 60Hz need to be used. 10kHz or higher frequency gives reasonable results.
3. Since the induction coil operates at other than line frequency, a DC power supply driving an oscillator is needed. Once you introduce a DC supply, it is relatively cheap and also useful to design it to produce a constant output voltage from a range of input voltages. Use of this design makes it possible to deliver the same heat output from 208 volt input as from 240 volt input, as long as the input current is allowed to rise.
1. Eddy currents result from a changing magnetic field in a conducting material with bulk resistance. For a given external magnetic field, a ferrous metal cooking vessel will have higher internal magnetic field, hence stronger eddy currents. The changing magnetic field tries to produce a compensating magnetic field caused by the eddy currents. This mechanism acts as a current source in the material, not a voltage source, for low resistances.
2. The heating due to the eddy currents will increase as the effective resistance of the pot surface increases. One way to do this is to concentrate the current in a thinner layer of the ferrous metal. One way to do this and still have a sturdy pot bottom is to make use of skin effect. To get a useful skin effect contribution, frequencies higher than 60Hz need to be used. 10kHz or higher frequency gives reasonable results.
3. Since the induction coil operates at other than line frequency, a DC power supply driving an oscillator is needed. Once you introduce a DC supply, it is relatively cheap and also useful to design it to produce a constant output voltage from a range of input voltages. Use of this design makes it possible to deliver the same heat output from 208 volt input as from 240 volt input, as long as the input current is allowed to rise.
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