Energy Processing and Smart Grid

CHAPTER 7DC MACHINES

7.1 INTRODUCTION

An electric machine is a link between electrical and mechanical systems. The conversion of electrical to mechanical systems is based on transferring voltage and current electrical quantities to mechanical quantities as torque and angular speed and vice versa. Generators and motors can be used interchangeably. Feeding a generator from the mains will convert it to a motor, while driving a motor with a prime mover will convert it to a generator. Generators or motors can be AC or DC machines.

DC and AC machines are subject to electromechanical energy conversion, which satisfies Lenz's, Faraday's or Lorentz's fundamental laws. We present herein a simple illustration of two principles on which such machines are developed:

• conductor moving in a uniform magnetic field
• current-carrying conductor in a uniform magnetic field

7.2 CONDUCTOR MOVING IN A UNIFORM MAGNETIC FIELD

The movement of a conductor in a magnetic field gives induced voltage in a conductor in the magnetic field, as shown in Figure 7.1 [1],

Figure 7.1 Conductor moving in a magnetic field.

(7.1)

where B is the flux density in Tesla or Weber/m², l is the conductor length (m), and V is the velocity of its movement in the magnetic field (ms⁻¹).

7.3 CURRENT-CARRYING CONDUCTOR ...