Homopolar motor

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Motor homopolar is a direct current electric motor with two magnetic poles, the conductor which always cuts the magnetic flux path in the direction of rotating the conductor around the fixed axis so that the conductor is perpendicular to the static magnetic field. The resulting EMF (Electromotive Force) is continuous in one direction, the homopolar motor does not require a commutator but still requires a slip ring. The name homopolar shows that the electrical polarity of the conductor and pole of the magnetic field is unchanged (ie, it does not require substitution).

Video Homopolar motor

Histori

Homopolar motor is the first electric motor built. This operation was demonstrated by Michael Faraday in 1821 at the Royal Institution in London.

In 1821, shortly after the Danish physicist and chemist Hans Christian ÃÆ'ËÅ"rsted discovered the phenomenon of electromagnetism, Humphry Davy and British scientist William Hyde Wollaston tried, but failed, to design an electric motor. Faraday, whom Humphry challenged as a joke, then built two devices to produce what he called "electromagnetic rotation". One of them, now known as a homopolar motor, causes a continuous circular motion generated by the force of a circular magnet around a wire expanded into a mercury pool in which a magnet is placed. The wire will then rotate around the magnet if supplied with current from the chemical battery. These experiments and findings form the foundations of modern electromagnetic technology. In his excitement, Faraday published the results. This tensed his mentor's relationship with Davy, due to his teacher's jealousy over Faraday's accomplishments, and was the reason for Faraday's assignment to other activities, which consequently prevented his involvement in electromagnetic research for several years.

B. G. Lamme described in 1912 homopolar machines rated as 2,000 kW, 260 V, 7,700 A and 1,200 rpm with 16 slip rings operating at a peripheral speed of 67 m/s. Unipolar generators with a value of 1.125 kW, 7.5 V 150,000 A, 514 rpm built in 1934 installed in US steel mills for the purpose of pipe welding.

Maps Homopolar motor

Principle of operation

Motor homopolar driven by Lorentz power. Conductor with current flowing through it when placed in a magnetic field perpendicular to a current that feels as force in a direction perpendicular to the magnetic field and current. This force provides torque around the rotation axis. Since the axis of rotation is parallel to the magnetic field, and the opposite magnetic field does not alter the polarity, no change is required to keep the conductor spinning. This simplicity is most easily achieved by single-loop design, which makes homopolar motors unsuitable for most practical applications.

Like most electro-mechanical machines, the homopolar motor can be reversed: if the conductor is rotated mechanically, it will operate as a homopolar generator, producing a direct current voltage between two conductor terminals. The resulting direct current is the effect of the homopolar properties of the design. Homopolar generators (HPGs) are extensively researched at the end of the 20th century as low voltage but DC power supplies are currently very high and have achieved some success on lighting up experimental railgun.

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Build simple homopolar motor

Homopolar motor is very easy to build. Permanent magnets are used to provide an external magnetic field in which the conductor will rotate, and the battery causes current to flow along the conductor wire. Magnets do not need to move, or even come into contact with the rest of the motor; the main purpose is to provide a magnetic field that will interact with the magnetic field induced by the current in the wire. One can attach the magnet to the battery and allow the conductor wire to rotate freely while closing the electrical circuit by touching the top of the battery and the magnet attached to the bottom of the battery. Cables and batteries can become hot if operated continuously.

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Gallery

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Example

• Railgun
• Ball bearing motor

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See also

• Homopolar generator
• The Barlow Wheel

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References

Source of the article : Wikipedia