Description of a Simple Dynamo: Component, Working and Principles and relate it to the Production of Hydro-Electric Power

A Simple Dynamo: Component, Working and Principles and relate it to the Production of Hydro-Electric Power – This article describes and discusses everything about Simple Dynamo. What is Dynamo, History of Dynamo, Components of Dynamo, Working and Principles of Simple Dynamo, How Dynamo relates to the production of Hydro-Electric power and other related concepts.

INTRODUCTION

The word Dynamo from “(from the Greek word dynamics: meaning power) was originally another name for an electrical generator and still has some regional usage as a replacement for the word generator. After the discovery of the AC generator and that alternating current can be used as a power supply. The word dynamo became associated exclusively with the communicated direct current electric generator while on AC electrical generator using either ship rings or rotor magnet would become known as an alternator.

A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry and the foundation upon which many other later electric power conversion devices were based including the electric motor, the alternating current alternator and the rotary converter. Today the simple alternator dominates large scale power generation for efficiency, reliability and cost reasons.

A dynamo has the disadvantages of a mechanical commutator besides; converting alternating current to direct current using power rectification devices (vacuum tube or more recently solid state.) is effective and usually economical.

The faraday disk was the first electric generator. the horseshoe shape magnet (A) created a magnetic field through the disk (D) when the disk centers toward the rim. The current flowed out through the sliding spring contact m, through the external circuit and back into the centre of the disk through the axle. The operating principle of electromagnetic generators was later called Faraday’s law, is that an electromotive force is generated in an electrical conductor which encircles a varying magnetic flux. He also built the first electromagnetic generator, called the Faraday- disk, a type of homopolar generator, using a copper disk rotating between the poles of a horseshoe magnetic. It produced a small DV voltage. This was not a dynamo in the current sense, because it did not use a commutator. This design was inefficient, due to self counseling counter flows of current in regions that were not under the influence of the magnetic field. While current was induced directly underneath the magnet, the current would circulate backwards in regions that were outside the influence of the magnetic field. This counter flow limited the power output to the pickup wires and induced waste heating the copper disk later, homopolar generators would solve the problem by using an array of magnets arranged around the disk perimeter to maintain a steady field effect in one current flow direction.

Another disadvantage was the output voltage was very low, due to the single current path through the magnetic flux. Faraday and others found that higher, more useful voltages could be produced by winding multiple turns of wire into coil. Wire windings can conveniently produce any voltage desired by changing the number of turns? So they have commutator to produce direct current. Independently of Faraday, (The Hungarian) Anyas Jedlik started experimenting in (1827) with the electromagnetic rotating devices which he called electromagnetic self-rotors. In the prototype of the single pole electric starter, both the stationary and the revolving parts were electromagnetic.

About 1856 he formulated the concept of the dynamo about six years before Siemens and Wheatstone but did not patent it as he thought he was not the first to realize this. His dynamo used, instead of permanent magnets, two electromagnets placed opposite to each other to induce the magnetic field around the rotor, it was also the discovery of the principle of dynamo self excitation.

COMPONENTS OF SIMPLE DYNAMO

Dynamo consists of 3 major components: the stator, the armature, and the commutator.

The stator is a fixed structure that makes magnetic field, you can do this in a small dynamo using a permanent magnet. Large dynamos require an electromagnet.

The armature is made of coiled copper windings which rotate inside the magnetic field made by the stator. When the windings move, they cut through the lines of magnetic field. This creates pulses of electric power.

The commutator is needed to produce direct current. In direct current power flows in only one direction through a wire, the problem is that the rotating armature in a dynamo reverses current each half turn, so the commutator is a rotary switch that disconnects the power during the reversed current part of the cycle. Brushes are part of the commutator, the brushes must conduct electricity as the keep contact with the rotating armature. The first brushes were actual wire “brushes” made of small wires. These wore out easily and they developed graphic blocks to do the same job.

 WORKING MODELS OF SIMPLE DYNAMO

Since the magnets in an dynamo are solenoids, they must be powered to work. So in addition to brushes which tap power to go out to the main circuit, there is another set of brushes to take power from the armature to power the stator’s magnets. That’s fine if the dynamo is running, but how do you start a dynamo if you have no power to start?

Sometimes the armature retains some magnetism in the iron core, and and when it begins to turn it makes a small amount of power, enough to excite the solenoids in the stator. Voltage then begins to rise until the dynamo is at full power.

If there is no magnetism left in the armature’s iron, than often a battery is used to excite the solenoids in the dynamo to get it started. This is called “field flashing”.

Below in the discussion of wiring the dynamo you will notice how power is routed through the solenoids differently.

PRINCIPLES OF SIMPLE DYNAMO

The generation of electricity by a dynamo is based on a principle of magnetism called induction. When the lines of force that pass from the north to the south pole of a magnet are cut by a wire there is produced or induced in the wire a current of electricity. That is, if we take a loop or coil of wire which has no current in it and a magnet which also has no current, and move the loop or coil between the poles, a momentary current is produced. If a series of loops or coils are used instead of one loop, a current may be generated continuously. This method of generating electric current is called induction.

The strength of a current in electromotive force set up by induction depends upon: (1) the strength of the magnet, (2) the number of turns of wire in the coil or loop, and (3) the speed with which the magnetic lines of force are cut, that is, the speed at which the coil rotates.

Direction of an Induced Current.

The direction of an induced current depends upon two factors: (1) the direction of the motion of the wire, and (2) the direction of the magnetic lines of force.

A very valuable method of determining the direction of current used in practical life is called Fleming’s Rule.

Place the thumb, forefinger, and center finger of the right hand so as to form right angles to each other. If the thumb points in the direction of the motion of the wire, and the forefinger in the direction of the magnetic lines of force, the center finger will point in the direction of the induced current.

It is very important to know the direction of the current in revolving a loop of wire between the poles of a magnet in order to understand the working of a dynamo.

Examine and notice the loop of wire between the poles of the magnet. If the loop is rotated to the right, the wire XB moves down during the first half of the revolution. According to Fleming’s Rule, the current would be directed from B to X. The wire YA would move up during the first half of the revolution and the current flow from A to Y. As the result of the first half of the revolution, the current would flow in the direction AYBX.

HOW DYNAMO RELATE TO THE PRODUCTION OF HYDROELECTRIC POWER

Hydroelectric power, electricity produced from generators driven by turbines that convert the potential energy of falling or fast-flowing water into mechanical energy

In the generation of hydroelectric power, water is collected or stored at a higher elevation and led downward through large pipes or tunnels (penstocks) to a lower elevation; the difference in these two elevations is known as the head. At the end of its passage down the pipes, the falling water causes turbines to rotate. The turbines in turn drive generators, which convert the turbines’ mechanical energy into electricity. Transformers are then used to convert the alternating voltage suitable for the generators to a higher voltage suitable for long-distance transmission. The structure that houses the turbines and generators, and into which the pipes or penstocks feed, is called the powerhouse.

Hydroelectric power plants are usually located in dams that impound rivers, thereby raising the level of the water behind the dam and creating as high a head as is feasible. The potential power that can be derived from a volume of water is directly proportional to the working head, so that a high-head installation requires a smaller volume of water than a low-head installation to produce an equal amount of power. In some dams, the powerhouse is constructed on one flank of the dam, part of the dam being used as a spillway over which excess water is discharged in times of flood. Where the river flows in a narrow steep gorge, the powerhouse may be located within the dam itself.

In most communities, electric-power demand varies considerably at different times of the day. To even the load on the generators, pumped-storage hydroelectric stations are occasionally built. During off-peak periods, some of the extra power available is supplied to the generator operating as a motor, driving the turbine to pump water into an elevated reservoir. Then, during periods of peak demand, the water is allowed to flow down again through the turbine to generate electrical energy. Pumped-storage systems are efficient and provide an economical way to meet peak loads.

In certain coastal areas, such as the Rance River estuary in Brittany, France, hydroelectric power plants have been constructed to take advantage of the rise and fall of tides. When the tide comes in, water is impounded in one or more reservoirs. At low tide, the water in these reservoirs is released to drive hydraulic turbines and their coupled electric generators (see tidal power).

Falling water is one of the three principal sources of energy used to generate electric power, the other two being fossil fuels and nuclear fuels. Hydroelectric power has certain advantages over these other sources: it is continually renewable owing to the recurring nature of the hydrologic cycle and produces neither atmospheric nor thermal pollution. Hydroelectric power is a preferred energy source in areas with heavy rainfall and with hilly or mountainous regions that are in reasonably close proximity to the main load centres. Some large hydro sites that are remote from load centres may be sufficiently attractive to justify the long high-voltage transmission lines. Small local hydro sites may also be economical, particularly if they combine storage of water during light loads with electricity production during peaks. Many of the negative environmental impacts of hydroelectric power come from the associated dams, which can interrupt the migrations of spawning fish, such as salmon, and permanently submerge or displace ecological and human communities as the reservoirs fill.

REFERENCES

“Ányos Jedlik biography”. Hungarian Patent Office. Retrieved 10 May 2009.

“Experimental Researches in Electricity,” Vol. 1, Series I (Nov. 1831); footnote for Art. 79, p. 23, ‘Ampère’s Inductive Results,’ Michael Faraday, D.C.L, F.R.S.; Reprinted From The Philosophical Transactions Of 1846-1852, with other Electrical Papers from the Proceedings of the Royal Institution and Philosophical Magazine, Richard Taylor and William Francis, Printers and Publishers to the University of London, Red Lion Court, Fleet Str., London, England (1855).

Volker Leiste: 1867 – Fundamental report on dynamo-electric principle before the Prussian Academy of Sciences

Williams, L. Pearce, “Michael Faraday,” p. 296-298, Da Capo series, New York, N.Y. (1965).

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