INDUCTION MOTOR
The invention of the induction motor has changed the history of human civilization. This type of
motor was invented by Nikola Tesla 100 years ago and even today it is the most
common and widely used motor all over the world. If you know it or not,
about 50% of global electric power consumption is due to induction motors.
motor was invented by Nikola Tesla 100 years ago and even today it is the most
common and widely used motor all over the world. If you know it or not,
about 50% of global electric power consumption is due to induction motors.
Let’s get into Nikola Tesla’s Great
thinking. There are two major parts in an induction motor – (i) STATOR
[Stationary Part] and (ii) ROTOR [Rotating Part].
thinking. There are two major parts in an induction motor – (i) STATOR
[Stationary Part] and (ii) ROTOR [Rotating Part].
The Stator is
basically, a three-coil winding and a three-phase A.C. power is given to it. The
winding passes through the slots of the stator which are made by stalking thin
highly permeable steel lamination inside a steel or cast iron frame. When a three-phase A.C. current passes through the winding of a motor, it generates a
Rotating Magnetic Field (RMF). This RMF causes the rotor to rotate to
understand how the RMF is generated, as well as its properties, have a look at the simple diagram of a three-phase A.C. motor.
basically, a three-coil winding and a three-phase A.C. power is given to it. The
winding passes through the slots of the stator which are made by stalking thin
highly permeable steel lamination inside a steel or cast iron frame. When a three-phase A.C. current passes through the winding of a motor, it generates a
Rotating Magnetic Field (RMF). This RMF causes the rotor to rotate to
understand how the RMF is generated, as well as its properties, have a look at the simple diagram of a three-phase A.C. motor.
Thethree wires are connected 1200 apart. A wire that is carrying
current produces a magnetic field around it. When a three-phase current is
given to this special arrangement, a magnetic field is produced. With a variation of
A.C. current, the magnetic field takes a different orientation.
If we compare In these three instances, we will observe that it is like a magnetic field with
uniform strands rotating. Engineers call the rotating speed of the magnetic field, synchronous speed. If we put a close conductor inside it, according to Farad’s
law as the magnetic field is varying, an EMF (Electro-Magnetic Force) will be
inducted into the loop. The EMF will produce a current into the loop. In this
way, the situation will be like a current-carrying loop situated in the magnetic
field. According to Laurence’s Force law, an EMF will be produced on the
loop and the loop will start rotating. The same thing happens inside an
Induction motor.
uniform strands rotating. Engineers call the rotating speed of the magnetic field, synchronous speed. If we put a close conductor inside it, according to Farad’s
law as the magnetic field is varying, an EMF (Electro-Magnetic Force) will be
inducted into the loop. The EMF will produce a current into the loop. In this
way, the situation will be like a current-carrying loop situated in the magnetic
field. According to Laurence’s Force law, an EMF will be produced on the
loop and the loop will start rotating. The same thing happens inside an
Induction motor.
Instead of a simple loop, a Squirrel cage is
used in a Rotor. When the three-phase A.C. current passes through the stator, it produces a rotating magnetic field. So as in the previous case, current will be
induced in the bars of the squirrel cage which is shorted by the end ring, and
the rotor will start rotating. For this reason, the motor is called an induction
motor. Electricity is induced on the rotor with the help of electromagnetic
induction rather than a direct connection. To get such electromagnetic induction, we should install insulated iron core lamina inside the rotor to reduce the current loss
used in a Rotor. When the three-phase A.C. current passes through the stator, it produces a rotating magnetic field. So as in the previous case, current will be
induced in the bars of the squirrel cage which is shorted by the end ring, and
the rotor will start rotating. For this reason, the motor is called an induction
motor. Electricity is induced on the rotor with the help of electromagnetic
induction rather than a direct connection. To get such electromagnetic induction, we should install insulated iron core lamina inside the rotor to reduce the current loss
The induction motor has a big advantage in that it is self-starting. The speed of an Induction motor is controlled by
controlling the power frequency.
controlling the power frequency.
Induction motors rule the industry as well as
it full-fills domestic need also because it has
it full-fills domestic need also because it has
(i)
NO PERMANENT MAGNET
NO PERMANENT MAGNET
(ii)
NO BRUSHES
NO BRUSHES
(iii)
NO COMMUTATOR RINGS
NO COMMUTATOR RINGS
(iv)
NO POSITION SENSORS.
NO POSITION SENSORS.
The most advanced feature of an induction motor is that the speed of the
induction motor is controlled by controlling the input power frequency which
mentioned earlier.
induction motor is controlled by controlling the input power frequency which
mentioned earlier.
