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Permanent Magnet


There are many properties of a permanent magnet that are considered in its design for a magnetic device, but most often it is the demagnetization curve that initially determines its suitability for the task. Its shape contains information on how the magnet will behave under static and dynamic operating conditions and in this sense the material characteristic will constrain what can be achieved in the device design.

The fundamental theory describing permanent magnets is similar to that for soft magnetic materials. A magnet is permanent (sometimes called hard) if it will alone support a useful flux in the air gap of a device, whereas it is soft if it can only do so with the aid of an external electrical or magnetic input. 

What is Permanent Magnet?

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The permanent magnet is a material which is made up of magnetized material and possess permanent magnetic field. Ferromagnetic materials are permanent magnet. Usually they are made up of alnico and ferrite.

How to make a Permanent Magnet?

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Permanent magnet can be produced by using below technique.
  • Consider a copper wire, steel rod, iron filings, dc power supply etc.
  • Steel rod is wounded using the wire and connect the ends to the power supply.
  • So the current is passing through this wire.
  • This create the magnetic field.
  • After switch off the power, this setup is placed near to the iron filings, it gets attracted.
  • So we conclude that this steel rod become a permanent magnet.

Types of Permanent Magnets

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The different types of permanent magnets are listed below :

1. Neodymium Iron Boron: They are the strongest magnet among the permanent magnets. It is known as rare earth magnets because the components are comes under lanthanides

2. Samarium Cobalt: It is a kind of rare earth magnet which has high magnetic strength and temperature resistant and has high resistance to oxidation.

3. Alnico:
The main constituent of the alnico is aluminum, nickel and cobalt. To increase the magnetic properties, small amount of other elements are added to this composition. It has high temperature stability and highly resistant to demagnetization.

4. Ceramic or Ferrite: This material is composed of iron oxide and barium or strontium carbonate. This is very brittle in nature.

Permanent Magnet Generator

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Permanent magnet generator is used to produce electricity which is made up of using permanent magnets. Permanent magnets are fixed to the rotor, this creates a rotational motion and hence produce the current. The main advantages and disadvantages of permanent magnet motors are listed below :

Advantages Disadvantages
Produce magnetic field without the current. Easy start and stop can't be possible.
Very simple to develop and less maintenance is required. Since magnetic flux is constant external force is required to start.
Produce electricity continuously. It is very difficult to regulate.
They can work continuously with out any distractions. Large permanent magnet is required to produce high electricity.

Permanent Magnet Motor

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A permanent magnet motor mainly consists of three parts; armature coil, rotor and stator. The working of these parts in a permanent magnet is described below :

Armature coil is placed in to the magnetic field of a permanent magnet. If the applied voltage is zero, rotor begins to rotate. This rotation causes the induced voltage in the coil. This current is responsible for the rotation of armature coil. While rotating the armature, a voltage is induced which nullify the applied voltage. This is the principle behind the permanent magnet motor. There are two types of permanent magnet motors; dc motors and ac motors.
Permanent Magnet Motor
Ac motors
In the case of permanent magnet ac motors, the ac current is produced and get converted in to mechanical energy. The principle is same as above and the parts are also same for this motor.

Dc motors
Here, dc current is converted in to mechanical work. Alnico and ceramic materials are used as the permanent magnet in this case. The given figure depicts the dc motor.
Permanent Magnet DC Motor

Permanent Magnet Alternator

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An alternator is nothing but the device which convert mechanical energy to electrical energy. So, in a permanent magnet alternator, permanent magnet is placed instead of an electromagnet. The current is in the form of ac.

Permanent Magnet Motor Free Energy

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It is nothing but the energy generated during the working of permanent magnet motor. In this case, there is no external energy to produce the current. The magnetic field generated induced the voltage in the coil hence produce the electric current. This current is responsible for the working of the permanent magnet motor.