Design of Rotating Electrical Machines, 2nd Edition

7

Properties of Rotating Electrical Machines

In this chapter we shall study the design and properties of the most important industrial electric machines, squirrel cage induction motors (IMs), different synchronous machines (traditional field-winding excited-synchronous machines (SMs), permanent magnet synchronous machines (PMSMs) and synchronous reluctance machines (SyRMs)), DC-machines and switched reluctance (SR) machines. The biggest attention is paid to IMs and SMs as they are the dominating machines in the industry. However, the importance of other machine types is also admitted.

Before entering into specific machine type properties, however, we will start by observing different loadings of the machines. First the relation of the machine speed and size and then mechanical, electrical and magnetic loadabilities are studied to find out the performance limits of different machine types.

7.1 Machine Size, Speed, Different Loadings and Efficiency

7.1.1 Machine Size and Speed

“Electro-mechanics” is the technology covering the design of electrical machines. The term itself indicates that in electrical machines there is an interaction between electromagnetism and mechanics. Actually, mechanics and material properties such as the yield strength dictate the dimensions and limiting speeds of the rotating parts in an electrical machine. As has been observed earlier the machine size is directly proportional to the torque of the machine. The torque is, of course, one of the most important ...