Designing a Multi-Setting Stove Using Resistive Heating

[jackashflash]

Homework Statement

Your first assignment with the Holmes Electronics Company is to help us design an efficient stove using resistive heating. Our market research tells us that the stove needs four heat settings: Hi, Med-2, Med-1, and Low. The Hi setting needs to have an electric power of 3 kW and the Med-1 setting needs to have an electrical power between 900 and 950 W. The error on these powers can be ± 2%.
A colleague has suggested that two resistive heating elements and a fuse are needed for this design. Assuming that the voltage for the stove 110 V, determine the following:

The resistance of the two heating elements to the nearest 1- (this is the best that our manufacturing process can do)
The value of the fuse to the nearest 0.5-A
The values of the four power settings

Homework Equations

V=IR
P=I*V

The Attempt at a Solution

High = 3000 W
Med2 = ?
Med1 = 925 W
Low = ?

I took the midpoint to find the Med2 = 1962.5 W & Low = 462.5 W

I envisioned that there are 4 switches for each temp setting, and then 2 switches for each heating element. The power at the heating elements would be controlled by 3 dependent current sources.

P/V = I1 = 4.2 amps
V=I*R R = 26.1622 ohms

Lo: No dependent current source
med1: dependent current source = 1*i1
med2: dependent current source = 3.24*i1
High: dependent current source = 5.49*i1

 

[rude man]

Remember the elements can be connected in series, in parallel, or they can be run stand-alone.

The elements are not controlled by current sources. The are controlled by 110V which is applied to them in series, to each by itself, or together in parallel. That permits 4 separate power dissipations.