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close this bookElectrical Machines - Basic Vocational Knowledge (IBE - Deutschland; 144 pages)
View the documentIntroduction
Open this folder and view contents1. General information about electrical machines
Open this folder and view contents2. Basic principles
Open this folder and view contents3. Execution of rotating electrical machines
Open this folder and view contents4. Synchronous machines
Open this folder and view contents5. Asynchronous motors
close this folder6. Direct current machines
View the document6.1. Constructional assembly
Open this folder and view contents6.2. Operating principles
Open this folder and view contents6.3. Operational behaviour of direct current machines
close this folder6.4. Circuit engineering and operational features of customary direct current generators
View the document6.4.1. Separate-excited direct current generator
View the document6.4.2. Direct current shunt generator
Open this folder and view contents6.5. Circuit engineering and operational features of customary direct current motors
Open this folder and view contents7. Single-phase alternating current motors
Open this folder and view contents8. Transformer
 

6.4.1. Separate-excited direct current generator

Circuitry

The separately excited direct current motor is a direct current generator whose exciter winding is fed by a separate voltage source.


Figure 100 - Circuitry and terminal board of a separately excited direct current generator

Voltage behaviour

The induced rotor current is virtually load independent given constant rotor speed and exciter flow. Conversely, terminal voltage U drops slightly as load increases. The graphical presentation of the function U = f (I) is a declining straight.


Figure 101 - Voltage curve of a separately excited direct current generator

The separately excited generator cannot be short-circuited.

Voltage - control

By means of the voltage field actuator the exciter flow can be altered from minimum to saturation value. Consequently, the induced voltage can be varied within considerable limits.

Application

Due to the considerable voltage setting range, the separately excited generator is utilised where very different voltages are required, for instance in converters.

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