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DC Machines
Page 2


DC Machines
Direct Current (DC) Machines Fundamentals
? Generator action: An emf (voltage) is induced in a
conductor if it moves through a magnetic field.
? Motor action: A force is induced in a conductor
that has a current going through it and placed in a
magnetic field.
? Any DC machine can act either as a generator or
as a motor.
Page 3


DC Machines
Direct Current (DC) Machines Fundamentals
? Generator action: An emf (voltage) is induced in a
conductor if it moves through a magnetic field.
? Motor action: A force is induced in a conductor
that has a current going through it and placed in a
magnetic field.
? Any DC machine can act either as a generator or
as a motor.
Simplest rotating dc machine
? It consists of a single loop of
wire rotating about a fixed axis.
? The rotating part is called rotor,
and the stationary part is the
stator.
? The magnetic field for the
machine is supplied by the
magnetic north and south poles.
With uniform air gap, the
reluctance is same under the
pole faces.
Page 4


DC Machines
Direct Current (DC) Machines Fundamentals
? Generator action: An emf (voltage) is induced in a
conductor if it moves through a magnetic field.
? Motor action: A force is induced in a conductor
that has a current going through it and placed in a
magnetic field.
? Any DC machine can act either as a generator or
as a motor.
Simplest rotating dc machine
? It consists of a single loop of
wire rotating about a fixed axis.
? The rotating part is called rotor,
and the stationary part is the
stator.
? The magnetic field for the
machine is supplied by the
magnetic north and south poles.
With uniform air gap, the
reluctance is same under the
pole faces.
The Voltage Induced in a Rotating Loop
? If the rotor is rotated, a
voltage will be induced in the
wire loop.
? The voltage on each segment
is given by eind =(vxB).l
? The total induced voltage on
the loop is: eind =2vBl
Page 5


DC Machines
Direct Current (DC) Machines Fundamentals
? Generator action: An emf (voltage) is induced in a
conductor if it moves through a magnetic field.
? Motor action: A force is induced in a conductor
that has a current going through it and placed in a
magnetic field.
? Any DC machine can act either as a generator or
as a motor.
Simplest rotating dc machine
? It consists of a single loop of
wire rotating about a fixed axis.
? The rotating part is called rotor,
and the stationary part is the
stator.
? The magnetic field for the
machine is supplied by the
magnetic north and south poles.
With uniform air gap, the
reluctance is same under the
pole faces.
The Voltage Induced in a Rotating Loop
? If the rotor is rotated, a
voltage will be induced in the
wire loop.
? The voltage on each segment
is given by eind =(vxB).l
? The total induced voltage on
the loop is: eind =2vBl
The Voltage Induced in a Rotating Loop
? When the loop rotates
through 180°,
?segment ab is under
the opposite pole face
?the direction of the
voltage on the
segment reverses
?its magnitude remains
constant
The resulting voltage e
tot
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FAQs on PPT - DC Machines - Electrical Machines - Electrical Engineering (EE)

1. What are the main types of DC machines used in electrical engineering?
Ans. The main types of DC machines used in electrical engineering are DC generators and DC motors. DC generators convert mechanical energy into electrical energy, while DC motors convert electrical energy into mechanical energy.
2. How does a DC generator work?
Ans. A DC generator works on the principle of electromagnetic induction. It consists of a rotor (armature) that rotates within a magnetic field created by stationary field coils. As the rotor rotates, the magnetic field cuts across the armature conductors, inducing an electromotive force (EMF) or voltage. This voltage can be collected from the armature terminals to obtain electrical power.
3. What are the applications of DC generators?
Ans. DC generators find applications in various industries and systems. They are commonly used in power plants, where they provide backup power during grid failures. They are also used in electric vehicles, battery charging systems, and portable generators. Additionally, DC generators are used in renewable energy systems, such as wind turbines and solar power plants.
4. How does a DC motor work?
Ans. A DC motor works on the principle of the Lorentz force. It consists of a magnetic field and a current-carrying conductor (armature). When a current passes through the armature, a magnetic field is created around it. This magnetic field interacts with the magnetic field produced by the stator (field coils), resulting in a rotational force (torque) that causes the motor to rotate.
5. What are the advantages of DC motors over AC motors?
Ans. DC motors have several advantages over AC motors in certain applications. Firstly, DC motors offer better speed control and torque characteristics, making them suitable for applications requiring precise control, such as robotics and automation. Secondly, DC motors can provide higher starting torque, making them ideal for applications with high initial loads. Lastly, DC motors are more efficient at lower speeds compared to AC motors, making them suitable for traction applications, such as electric vehicles and elevators.
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