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Factors Controlling the Speed

8.1 Factors Controlling the Speed

D.C. machines are generally much more adaptable to adjustable speed service. The ready availability of D.C. motors to adjustment of their operating speed over wide ranges and by a variety of methods is one of the important reasons for the strong competitive positions of D.C. machinery in modern industrial applications.

The speed of a D.C. motor can be expressed by the following relationship.5

Therefore, the speed of D.C. motor can be regulated by changing ΙΈ, R or V, or in other words, by,

1.Field control

2.Rheostatic control

3.Voltage control.

Note. Thyristor control of D.C. motor is out of scope of this book.