Appendix

# Solutions to review questions

## Chapter 1

1. (1) The magnetomotive force or m.m.f. is simply the product of the number of turns and the current, i.e. m.m.f. = 250 × 8 = 2000 AT. The ‘AT’ stands for ampere-turns, but strictly the unit of m.m.f. is the Ampere.
2. (2) We are told that the magnetic circuit is made of good-quality magnetic steel, which is a coded way of saying that the reluctance of the steel part of the magnetic circuit is negligible in comparison with the air-gap. Under these circumstances all of the m.m.f. provided by the coil (2000 A) is available across the gap, and the flux density in the air-gap is given by Eq. (1.7) as

$B=\frac{{\mu }_{o}\mathit{NI}}{g}=\frac{4\pi ×{10}^{-7}×2000}{2×{10}^{-3}}=1.26\mathrm{T}.$

The question then asks about the flux density in the iron, implying that it ...

Get Electric Motors and Drives, 5th Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.