Electrical Machines and Systems: the Challenge for a Culture of Self-Reliance
Nature has provided a range of fundamental forces which the early man had to appreciate: the natural electric force, gravitational or earth's magnetic force, coulomb's force and frictional force. Attempts to understand and harness these forces led to the birth of modern science, engineering and technology. Electricity and magnetism were soon found to be inter-related and can be transformed into each other. Material scientists and Astrologers found common grounds in the structure of the atom and the solar system. It is the gravitational force that makes the moon move round the earth day after day. All bodies consist of charged atoms, which obey the inverse square law of coulomb's force, and the atom in its structure can be said to be a miniature solar system. Just as an atom is a miniature solar system, the constellation of the solar system is often described as a big atom. It becomes clear that life was held together through the activities of rotation and balance of forces. At the centre of the earth the gravitational force reaches its maximum strength and ensures that the earths crust does not disintegrate. The rotating electrical machine is a product of an attempt to harness the reaction between electric and magnetic fields to do useful work. A number of forces in a rotating electrical machine are carefully controlled or suppressed to enable one harness the energy of rotation. Extensive application of electricity in today's modern industrial society could not have been possible without the benefit of certain types of materials. The ability of some materials to conduct electricity freely, slowly in other or with extreme difficulty in yet other types of materials classify materials into conductors, semi-conductors and insulator . Magnetic and nonmagnetic materials are also vital for the electromagnetic and other structures of electrical machines.