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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
close this folder6.2. Operating principles
View the document6.2.1. Power generation (direct current motor)
View the document6.2.2. Torque generation (direct current motor)
View the document6.2.3. Armature reaction (rotor reaction)
View the document6.2.4. Excitation
View the document6.2.5. Value relations
Open this folder and view contents6.3. Operational behaviour of direct current machines
Open this folder and view contents6.4. Circuit engineering and operational features of customary direct current generators
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
 

6.2.5. Value relations

A voltage U0 is always generated in the rotor circuit irrespective of the type of direct current machine. The windings in the operating field yield an ohmic resistor, the internal resistor R1. Both values can feature in a duplicate circuit plan.


Figure 94 - Duplicate rotor circuit

The internal resistance of the rotor circuit stems from

R1

rotor winding resistance

RW

interpole winding resistance

RK

compensation winding resistance

RB

brush resistance and series excitation

RR

series winding resistance

In accordance with the voltage law the duplicate circuit establishes the relations between generator and motor operating voltages:

U0 = U + U1

U = U0 + U1

The natural direction change in switching over from generator to motor operation must be heeded when drawing up the equations.

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