Electrical Machines - Basic Vocational Knowledge (IBE - Deutschland; 144 pages) Introduction 1. General information about electrical machines 2. Basic principles 3. Execution of rotating electrical machines 4. Synchronous machines 4.1. Operating principles 4.2. Constructional assembly 4.2.1. Stator 4.2.2. Rotor 4.3. Operational behaviour 4.4. Use of synchronous machines 5. Asynchronous motors 6. Direct current machines 7. Single-phase alternating current motors 8. Transformer

#### 4.2.2. Rotor

As regards rotor shape, one differentiates between the turbine and salient pole machines. Both rotor types feature a magnetic constant field. For this reason the rotor iron need not be a lamella pack.

The rotor of the turbine-type machine is called a non-salient pole rotor. It is cylindrically set up, rather long and has a relatively small diameter of up to some 1200 mm. A non-salient pole rotor only has a relatively small number of poles. Mainly it only features one pole pair, that is to say a north and south pole. As this machine mainly runs on alternating voltage of f = 50 Hz, this results in a considerable rotor speed. Thus, for example, a synchronous machine with one pole pair and alternating current at a frequency of f = 50 Hz, requires a speed of 3000 rpm.

Figure 39 - Two-pole non-salient pole rotor

The salient pole machine features a field spider with distinct poles which bear the exciter winding. This is relatively short and has a big diameter of some 10 m. The considerable number of pole pairs yield speeds of 60 rpm to 750 rpm given alternating voltage at a frequency of f = 50 Hz.

Figure 40 - Six-pole salient pole rotor

1 Field spider