To your cauldrons, ready, modulate!

When using your stove, did you notice the behavior of the cooking elements? Perhaps you observed a cooking element turn off when it was set to maximum intensity. Why is this so?

The heating power of a heating element is fixed by its resistance and the supply voltage. As long as it isenergized, the heating element produces a fixed amount of heat. How do you obtain different settings such as “minimum", "medium" or "maximum" and different thermal intensities? The typical way to modulate the heat is to modify cyclically the duration of the operating periods.

This mode of operation is illustrated below with graphs. By varying the duration of the operating periods, the internal control varies the average represented by the dotted horizontal line:

Source: https://sin.ledantec-numerique.fr/wp-content/uploads/cours_MLI.pdf

The first graph on the left shows that the operating period is short, which corresponds to the minimum position. The second graph presents a control operating at medium and the third, a control operating at maximum intensity. Operating at maximum intensity includes a short period of downtime, which is why you can see a heating element set to maximum turn off.

This mode of control has its advantages and disadvantages. This is a simple and economical way to control heating elements with fixed characteristics. This type of operation allows to obtain different heat intensities for the cooking elements and to simmer or cook favorite dishes successfully. 

Enjoy your cooking!

By Etienne Lemire, P. Eng., CFEI
Electrical Engineering | Fires | Explosions | Failures