"Bert Hyman" > wrote in message
...
> In "Douglas Reynolds"
> > wrote:
>
>> Anderson noted that an oven's heating elements are either on at full
>> power or off-with no middle ground.
>
> In this age of cheap semiconductors, why ->don't consumer ovens have
> "proportional controls"?
>
> I'd think that solid-state temperature controls would be cheaper and
> more reliable than the relay switching that's used now.
>
> Or, maybe the newest ones do; our Thermador oven is 5 years old.
>
> --
> Bert Hyman St. Paul, MN
Solid state power control is basically like what you get with a light dimmer
switch. The sinusoidal voltage is turned on and off during the sine wave to
achieve a reduction in power. In the oven the relay switches the power on
and off too, but since heat in the oven reacts more slowly than a lightbulb
on the retina, the switching can be done slower too. So there's really no
benefit in applying the technology. Relays seem to be good enough that they
don't need service also.