Generators

The word "generate" is a transitive verb. It means to bring into existence, produce, or evolve. From this parent word, we move on to the noun "generators," which refers to a begetter. It is an apparatus for producing gases, steam, etc. It is a machine for converting mechanical into electrical energy.

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Electric Generator
By electrical generator, we refer to a device by which mechanical energy is converted to electrical energy. To do so, the usual procedure is to use electromagnetic induction. The mechanical energy comes from a reciprocating or turbine steam engine, water tumbling through the turbine or water wheel, an internal combustion engine, a wind turbine, a hand crank, or any other suitable source of mechanical energy. Scientific experiments often require high voltage, and for this purpose, electrostatic generators are in demand. It is difficult to insulate machines producing very high voltages, and for this reason, electrostatic generators are manufactured only with low power ratings. Thus, these could not be used to generate huge quantities of electric power required for commercial consumption. Generators hitherto used electrostatic principles before the establishment of the connection between magnetism and electricity. Today, some electrostatic machines use either of the two mechanisms. In one case, the charge is transferred from a high-voltage electrode and in the other, charge is created by turboelectric effect using the principle of separation of two insulators wherein the belt leaves the lower pulley. Faraday pointed out that a potential difference is created between the ends of an electrical conductor that moves perpendicular to a magnetic field. The outcome of it all was the production of a small DC voltage coupled with large amounts of current.

Dynamos
The Dynamo gave a dynamic push to the world. It ranked first among electrical generators to give power for industrial use. It uses the principles of electromagnetism, by which mechanical rotation is converted into an alternating electric current. The dynamo consists of a stationary fixture that generates a strong magnetic field. A set of windings rotates within that field. In comparatively small machines, the magnetic field is provided by permanent magnets. But in the case of bigger machines, the field has to be created by electromagnets. The basic principle consists of converting alternating current to direct current. Many turns of serially connected wire are used in the rotating windings of a dynamo. It causes the terminal voltage of the machine to be higher than what a disc can produce. In this way, electrical energy can be delivered at a voltage that is convenient to the user. The connection between mechanical rotation and electric current in a dynamo is reversible. One dynamo could cause a second dynamo that has been connected to it to rotate if current is fed through it.

A Simple Electric Generator
Before going into the market to shop for a generator, it is wise to know as much about it as you can. Otherwise, you will be groping in the dark. The best way to gain first-hand knowledge is try your hand in making a small generator capable of lighting a small incandescent light bulb. The generator is made from a cardboard box whose ends are hollow. Fix a nail through the center. The box has many turns of fine copper wire wound around it. Large magnets are clamped around the nail. With your hands, tightly spin fast the nail and magnets. See the bulb light up dimly. Remember to use strong magnets, plenty of fine wire, and a light bulb, which is of a special variety and needs only ½ volts. Hook the wires directly to the bulb. In this way, the mini generator will produce AC or alternating current. The magnets must be large and strong. Smaller varieties will not work.

Hybrid Generators
There is a continuous change in the way Man is using electricity. The main attention is on reduction of fuel consumption and maintenance costs. In keeping with this emphasis, generators have to be reliable, par excellence, and auto-generated. All these demands produced the hybrid generator. So far, most of the engine powered electric generators run continuously using huge quantities of fuel. A hybrid generator automatically gets switched off during periods of low demand. When power from the engine is needed, it automatically gets restarted, running at minimum RPM providing maximum fuel economy. Thus, this leads to remarkable savings in fuel, low maintenance requirements, and longer life for the engine. The hybrid generator consists of a controller, combustion engine, DC generator, batteries, and an Inverter – DC to AC. The stored DC power is converted to AC electric power, which can be used.

Battery Storage Systems
The system of battery storage helps the engine absorb load spikes. There is a controller, which is a sort of policeman, starting and stopping the engine traffic, as and when needed. The added advantage is that since hybrid generators are already fitted with an inverter and battery storage system, power coming from wind or sun can be connected directly to them. This will lead to greater efficiency and a bonus point from society at large. It is not just power that is needed, but quality power. Many high RPM varieties of generators are not quite up to the mark, because the voltage being produced is erratic and the poor quality sine wave causes damage to the machine. On the other hand, hybrid generators produce high quality power using the proper type of sine wave inverters capable of working even the most sensitive electronic equipments.

The Concepts
The concept to bear in mind about generators is that the generator moves an electric current, but it does not create an electric charge. Electric charge is already present in the conductive wiring of its windings. You can compare the generator to a water pump. The latter creates a flow of water, but does it make water inside? Certainly not! There are many other types of electrical generators based on other electrical principles like piezoelectricity and magneto-hydro-dynamics. The dynamo is akin to the electric motor in construction, and all ordinary types of dynamos can work as motors.

Terms
Either mechanical or electrical terms can be used to refer to the parts of a generator/dynamo. There are two distinct sets of terminology used interchangeably or in combinations. One term is mechanical and the other is electrical. Naturally, this leads to great confusion, especially when working with compound machines such as brushless alternators. It also is confusing while talking with personnel who are used to dealing with machines that are configured differently from the one the speaker is referring to. As a result, the buyer should be conversant with the terms frequently used before getting into a dialogue with the salesman. The rotor is a mechanical term referring to the rotating part of a generator. The stator is also a mechanical term referring to the stationary part of the generator. Electrical terms are armature and field. The first is a power-producing part of a generator and can be either the rotor or the stator. The field refers to the magnetic field of the generator. It can be on either side of the rotor or the stator and may be either electromagnetic or permanent magnetic.

Power
The generator is a source of electrical energy and as such, the maximum power theorem is applicable to it. According to it, the maximum power can be received from the generator by making the resistance of the load equal to that of the generator. In this instance, the power transfer efficiency is only 50%. In other words, half the power that is being generated is wasted in the form of heat and Lorentz force or back EMF inside the generator. This is why practical generators are not fashioned to work at maximum power output levels, but at a lower output where efficiency is considerably greater. Previously, motor vehicles used DC generators with electro-mechanical regulators, which were neither reliable nor efficient. These models have now given way to alternators with built-in rectifier circuits. These power the electrical systems of the vehicle and recharge the batteries after charging. Latest models of cars now have electrically powered steering assistance and air conditioning. This puts a great load on the electrical system. Vehicle alternators do not generally use permanent magnets. These can achieve efficiency levels of up to 90%, covering a wide speed range by controlling the voltage field. Alternators of motorcycles use permanent magnet stators made with rare earth magnets. These magnets can be made smaller and of lighter weight than other types. Bicycle lights are powered by some of the smallest type of generators. These have permanent magnet alternators supplying minimum of power. The rider provides the power with his or her muscles, and thus efficiency is at its best. These use rare-earth magnets and are fashioned in a precise manner. However, because of the permanent magnets, efficiency is around 60%. A battery would be necessary to control electromagnetic field, but due to its weight, this cannot be done. Sailing yachts use generators powered by the wind or water. There are trickle-charge batteries fitted for this purpose. A small propeller, wind-turbine, or impeller is connected to a low power alternator and rectifier to produce currents of up to 12A at standard cruising speeds. Quality of the electrical wave is important when operating sensitive electronic equipment. A power conditioner can turn the square wave generated into a smoothed out sine wave. Strange but true – human muscle can also empower the generater and is used in field radio stations.

Miscellaneous Generators
One type is the engine generator used in radio stations and works only when radio signals were sent. The receiver can operate on battery power. In Dubendorf Museum, there is a hand-driven electric generator. An engine generator is the amalgam of an electric generator and an engine mounted together to form a single unit. This combination is also called a gen-set or generator set. Apart from the engine and the generator, engine generators also have a fuel tank, an engine speed regulator, and a voltage regulator. Some models are fitted with a battery and electric starter. Standby power producing units often have automatic starting systems and a transfer switch to disconnect and connect the load, as and when required. Engine generators produce direct current, alternating power used to substitute for the power that might otherwise be purchased from a utility power station. Both single and three phase models are available in the market. The generator voltage, frequency, and power are measured as volts, Hz, and watts respectively. The ratings are chosen to suit the load to which it will be connected. The power ratings of engine generators are wide. Small hand portable models can supply many hundred watts of power. Handcart mounted varieties can supply thousands of watts, and stationary or trailer mounted models can supply over a million watts. The smaller units feed on gasoline, and the larger ones usually run off diesel, natural gas, and or propane or liquid gas. Most of the portable models are of the single-phase power variety, and most of the three-phase generators are the large industrial models. There are models of electrical generators which can be held in the palm of the hand. These come in handy while supplying energy to discharged car batteries and are known as emergency vehicle generaters. Then, there are emergency generaters to produce light while fighting fire or undertaking rescue operations.

At the end of the story on generators, the question arises – where are generators often used? In places where power is needed only temporarily such as construction sites, amusement parks, and travelling circuses. However, standby power generators are kept permanenty installed to supply power to critical loads during temporary breakdown of main power supply units. On the list are hospitals, communications services, sewage pumping stations, etc. Mini and midi generators are in great demand in developing countries where power supply is a perennial problem. Ultimately, in our search for an answer to the question of what is the mightiest generator of all generators, we have to look to Mother Nature with her powers of the wind, the sun, the water, and the latent force in the soil and earth to find the answer.


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