Many electric stovetops are operated by an infinite switch, which pulses the current on and off for intervals determined by the dial setting. The actual control is effected via a bi-metal switch that moves as it is heated. I was wondering whether the temperature of the heating element has any effect on the timing of the switch. In other words, if I put a pot of cold water on the stove, thereby lowering the resistance of the element, will that speed up the heating of the bi-metal in the switch, causing it to stay on longer? Or is the bi-metal heated by a completely separate circuit?
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Very revised answer:
I originally could not find a diagram of the internal connections of an "infinite switch" anywhere. Based on what is written elsewhere it sounded as if the heating coil connected across AC mains. However, this diagram which Dave found on this very interesting fire investigation site tells a different story.
More detail below, but a surprising conclusion is that
You asked about affect of load (eg pot) on element power.
The above lower ower wity more Watts element effect suggest manufacturers may want to make switches to suit element powers.
The electronic circuit below dos not depend o an element in series with the element, unlike the mechanical one.
The switch's heater element is IN SERIES with the range element.When the heater is cold the switch is on and the range element will be turned on. The heating energy will be governed by the element current which will depend on the element' Wattage. So doubling the wattage doubles the current.
This means that a higher Wattage element will reduce output for a given setting and have an increasing date of getting hot a the top end.
No - the temperature of the heating element or an item being heated has no effect on these controls. Here in New Zealand one name they are called is a "simmerstat" or an "energy regulator"- they will probably have other names elsewhere.
They are what is known as "open loop" controls. Only the dial setting controls the on/off ratio - the load or target object is NOT "sensed". As the dial is turned the on/off or mark-space ratio changes.
Controllers do exist that take account of the target temperature. This is usually termed a thermostat if you are heating air. These also may use a bimetallic strip but it is controlled by the target air temperature.
Here is an elecronic simmerstat control schematic. Note that they could sense load power but have chosen not to. OM1895 IC - diagram from here.