AC GENERATOR

                                         AC GENERATOR 

The Phenomenon of electromagnetic induction has been technologically exploited in many ways. An exceptionally important application is the generation of alternating currents (AC).

~ BASIC DESIGN 

The basic elements of an ac generator are shown in Figure. 

• It consists of a coil mounted on a rotor shaft. 

• The axis of rotation of the coil is perpendicular to the direction of the magnetic field. 

• The coil (called armature) is mechanically rotated in the uniform magnetic field by some external means. 

• The rotation of the coil causes the magnetic flux through it to change, so an emf is induced in the coil. 

• The ends of the coil are connected to an external circuit by means of slip rings and brushes.

 

PRINCIPLE 

One method to induce an emf or current in a loop is through a change in the loop’s orientation or a change in its effective area. WORKING The working of this generator can be seen in the following ways : • As the coil rotates in a magnetic field B  , the effective area of the loop (the face perpendicular to the field) is A cos , where  is the angle between A  and B  . This method of producing a flux change is the principle of operation of a simple ac generator. An ac generator converts mechanical energy into electrical energy. • When the coil is rotated with a constant angular speed , the angle  between the magnetic field vector B  and the area vector A  of the coil at any instant t is  = t (assuming  = 0° at t = 0)

 • Since the value of the sine function varies between +1 and –1, the sign, or polarity of the emf changes with time. • We can see from the figure that the emf has its extreme value when  = 90° or  = 270°, as the change of flux is greatest at these points. • The direction of the current changes periodically and therefore the current is called alternating current (ac). Since = 2v, the equation  =  0 sin t can be written as  =  0 sin 2vt, where v is the frequency of revolution of the generator’s coil. This gives the instantaneous value of the emf and varies between +0 and –0 periodically