Cover Image
close this bookElectrical Machines - Basic vocational knowledge (Institut für Berufliche Entwicklung, 144 p.)
close this folder6. Direct current machines
close this folder6.5. Circuit engineering and operational features of customary direct current motors
View the document6.5.1. Direct current motor with permanent excitation
View the document6.5.2. Direct current series motor
View the document6.5.3. Direct current shunt motor

6.5.1. Direct current motor with permanent excitation

Circuitry

The permanently excited direct current motor is a small machine in which the exciter field is established through permanent magnets.


Figure 104 - Circuitry and terminal board of a direct current motor with permanent excitation

Dependence of current take-up on the torque (load)

As the curve I = f (M) indicates in Figure 105, current take-up is directly proportional to the torque because of the constant exciter flow.


Figure 105 - I = f (M); Current take-up dependence on torque

Dependence of speed on the torque (load)

Direct proportionality exists between speed and torque in speed-load behaviour.


Figure 106 - n = f (M); Speed dependence on torque

Speed control

Speed control ensues by changing the applied voltage.

Application

Direct current motors with permanent excitation are used mainly for power ratings up to 500 W. Such motors find application in the toy industry, household appliances, measurement and control technology.