Question

What is the formula of the length of the magnet?

(a) length of the magnet = sum of the volume of air gap and magnet * Area of the magnet + 0.06

(b) length of the magnet = sum of the volume of air gap and magnet / Area of the magnet + 0.06

(c) length of the magnet = sum of the volume of air gap and magnet / Area of the magnet – 0.06

(d) length of the magnet = sum of the volume of air gap and magnet * Area of the magnet – 0.06

The question was posed to me in an interview for job.

I would like to ask this question from Design Steps and Considerations topic in section Design of Permanent Magnet (PM) DC Motors of Design of Electrical Machines

Answer 1

Right answer is (c) length of the magnet = sum of the volume of air gap and magnet / Area of the magnet – 0.06

The explanation is: The sum of the volume of the air gap and magnet is first calculated. Next, the area of the magnet is calculated from its formula and on substitution gives the length of the magnet.