DC Motor For students of the second stage in the Department of Electrical Engineering Introduction by Salam Mohammed Atiyah Master of Electrical Engineering

Objectives of the Lecture: 1. Introduction for Motors 2. Basic Principles for DC Motors 3. Construction of DC Motors 4. Types of DC Motors

The DC motor is electrical machine used in the converts of electrical energy into mechanical energy DC Motors

Basic Principles for DC Motors The interaction of current flowing in the conductor and the magnetic field will produce mechanical force conductor magnetic field Battery

The direction of motion can be found using Fleming’s Left Hand Rule. The first finger points in the direction of the magnetic field. The second finger points in the direction of the current in the wire The thumb then points in the direction of the move N S S N

Stator Rotor Field Windings: generates the magnetic field Armature Windings : are the winding in which the voltage is induced

Construction of the DC motor 1-Stator: contains of : Field coils Main poles Yoke

commutator Shaft Armature winding 2-Rotor: contains of Armature winding Commutator Shaft Brushes

Separately excited Separately excited DC motors DC motors Self excited DC motors DC motors Types of DC motor Shunt motor long shunt long shunt short shunt short shunt Series motor Series motor Compound motor

Self excited DC motors: A. 1.Self excited DC motors: A. Series DC motor The field winding and armature winding are connected in series. A N S + _ EaEa RaRa N sr R sr ItIt IaIa VtVt V t = E a + I a (R a + R sr )

B. Shunt DC motor The armature and field winding are connected in parallel. R fc R fw EaEa RaRa +Vt_+Vt_ ItIt IfIf IaIa I t = I a + I f V t = I a R a + E a E a = K a ϕ w m = V t – I a R a

EaEa RaRa R fc R fw NfNf N sr R sr EaEa RaRa R fc R fw NfNf N sr IfIf ItIt IaIa IaIa IfIf ItIt R sr V t = E a + I a R a +I t R sr V t = E a + I a (R a + R sr ) I t = I a + I f C. Compound DC motor: a. long shuntb.short shunt

2.Separately excited machines: The armature and field winding are electrically separate from each other. The field winding is excited by a separate DC source.

IfIf Field Winding DC Voltage V t VfVf EaEa RaRa VtVt + V f R fc R fw R fc IaIa ItIt

Thank you