The document discusses direct current (DC) motors. It explains that a DC motor converts electrical energy to mechanical energy when a current-carrying conductor is placed in a magnetic field, causing a torque. The direction of rotation reverses if the current direction is reversed. Factors like the number of poles and flux per pole affect the motor's speed. The document also describes methods of controlling the speed of a DC motor, including armature control and voltage control.

2. DC MOTOR
An electric motor is a machine which converts
electrical energy into mechanical energy.

3. The Pennsylvania
Railroad's class DD1
locomotive running gear
was a semi-permanently
coupled pair of third rail
direct current electric
locomotive motors built
for the railroad's initial
New York-area
electrification when
steam locomotives were
banned in the city
FROM HISTORY

4. PRINCIPLE OF DC MOTOR
When a current carrying conductor is placed in a magnetic field, it
experiences a torque and has a tendency to move known as motoring
action.
If the direction of current in the wire is reversed, the direction of
rotation also reverses.
When magnetic field and electric field interact they produce a
mechanical force, and based on that the working principle of dc
motor established.

5. DIRECTION OF DC MOTOR
The direction of rotation of a this motor is given by Fleming’s left
hand rule
It states that if the index finger, middle finger and thumb of your
left hand are extended mutually perpendicular to each other and if
the index finger represents the direction of magnetic field, middle
finger indicates the direction of current, then the thumb represents
the direction in which force is experienced by the shaft of the dc
motor.

7. FACTORS AFFECTING DC MOTOR
Where, P = no of poles
φ = flux per pole
Z= No. of conductors
A = No. of parallel paths
and N is the speed of the DC Motor.

8. METHODS OF SPEED CONTROL OF DC MOTOR

9. ARMATURE CONTROL METHOD

10. VOLTAGE CONTROL METHOD
Multiple voltage control: In this method the, shunt filed is
connected to a fixed exciting voltage, and armature is
supplied with different voltages. Voltage across armature
is changed with the help of a suitable switchgear. The
speed is approximately proportional to the voltage across
the armature.

11. SIMULINK