Page 221 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

DC Motor principle and types

Objectives: At the end of this lesson you shall be able to:
• explain the working principle of a DC motor
• state the different types of DC motor construction, working principle of 2 point 3 point and 4 point starts
• state the necessosty of series shunt is compound motor its application
• explain speed control methods of a DC motor.

Basics of dc motors
A DC moor is a machine which converts DC electrical energy in to mechanical energy
Working principle
Whenever a current carrying conductor is kept in a uniform magnetic field, a force will be setup on the conductor
so as to move it at right angle to the magnetic field.

Significance of the back E.M.F.
Back emf Eb = (ΦZN/60) x (P/A)
Voltage equation:
V = Eb + IaRa

Power equation
V Ia = EbIa + Ia2Ra
EbIa = Electrical equivalent of mechanical power Pm developed in the armature
Ia2Ra = Copper loss in the armature.
TORQUE

The turning twisting moment of force about an axis
Let Force is F Newton

CITS : Power - Electrician & Wireman - Lesson 1

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