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Electrical Machines-I
ECE-2207
Fariya Tabassum
Assistant Professor, Dept. of Electrical & Computer Engineering
Rajshahi University of Engineering & Technology, Rajshahi-6204
“Read! In the name of thy Lord and Cherisher, Who created-”.
[Sura Al-’Alaq ]
Study Materials
For Basic Knowledge
- Electric Machines -Theory, Operation, Application and Control
Charles I. Hubert - Electric Machinery Fundamentals
Stephen J. Chapman
For Govt. Job of BD
- A text Book of Electrical Technology (Volume II)
B. L. Theraza, A. K. Theraza - Principles of Electrical Machines
V. K. Mehta, Rohit Mehta
Magnetic Field is the Heart of Electrical Machines
So, Let’s see how it can be generated!
Magnetic Field
Magnetic field can be generated by
a. A permanent magnet
The direction of the magnetic field supplied by a magnet is from the north pole to the south pole but is south to north within the magnet itself, i.e., the flux forms a closed loop.
Magnetic Field
b. A current (both static and time varying) carrying conductor
The direction of the magnetic field around a current can be determined by the right-hand rule: Grasp the conductor with the right hand, with the thumb pointing in the direction of conventional current and the fingers will curl in the direction of the magnetic field.
Magnetic Field
c. A current (both static and time varying) carrying coil of wire
The direction of the magnetic field generated by a current through a coil of wire is also determined by the right-hand rule. Grasp the coil with the right hand, with the finger curled in the direction of the current and the thumb will point in the direction of the magnetic field.
Magnetic Field
Magnetic fields are the fundamental mechanism by which energy is converted from one form to another in motors, generators and transformers. The basic principles that describe how magnetic fields are used in these devices are:
- A time-changing magnetic field induces a voltage in a coil of wire if it passes through that col. (Basis of transformer action.)
- A current-carrying wire in the presence of a magnetic field has a force induced on it. (Basis of motor action.)
- A moving wire in the presence of a magnetic field has a voltage induced in it. (Basis of generator action.)
Basis of Transformer Action
A time-changing magnetic field induces a voltage in a coil of wire if it passes through that col.
The Direction of the Induced Voltage is determined by Lenz’s Law
Basis of Motor Action
A current-carrying wire in the presence of a magnetic field has a force induced on it.
Fleming’s Left Hand Rule for Motor
Basis of Generator Action
A moving wire in the presence of a magnetic field has a voltage induced in it.
