Introduction to Electric Generators

1. Introduction to Electric Generators

• A generator is a device that converts mechanical energy into electrical energy. It is opposite to electric motor that converts electrical energy to mechanical energy.
• The first generator was introduced by British scientist Michael Faraday in invented in 1831 which is commonly known as the Faraday disk.
• Generators are mainly used to deliver power to electric grid stations. The produced electrical power goes through high-voltage transmission lines that stretch across the country.

• Before high voltage electrical charge reaches the houses, it goes through a substation, where some steps are applied to lower down the voltage in order to make it reliable and feasible for domestic purposes.

• The electric generator gets mechanical power from a rotating shaft and is equal to the rotational, or angular, velocity multiplied by the shaft torque.
• The speed and construction of the electric generator mainly depend on the characteristics of the mechanical prime generator.
• The generators driven by steam turbines are commonly used in solar thermal electric power plants, waste incineration plants, coal, geothermal, natural gas power plants. They are also excessively used in paper, chemicals, cement, sugar, and steel industries.

2. Generator Working Principle

• The generator working principle is mainly based on electromagnetic induction which is the process of producing induced current in a closed circuit or in a coil by changing the magnetic field linked with the coil.

• This process was discovered by Michael Faraday who stated when a conductor is put in a varying magnetic field keeps, it produces a voltage across the electrical conductor which is also known as EMF (Electromotive Force).

3. Generator Construction

• A single rectangular copper made up of coil is allowed to around its own axis in a varying magnetic field provided by either electromagnet or a permanent magnet.
• The two ends of the coil are combined with two split-rings that are insulated from the central shaft and from each other.
• Two collecting brushes made up of carbon or copper are used to press against the slip rings.

• AC Generators
• DC Generators

• The working principle, however, is the same in both cases with the main aim to convert mechanical energy to electrical energy where the turning of a coil in a magnetic field produces EMF on both sides of the coil.
• Generators are mainly driven by diesel engines, water turbines, or steam turbines to convert energy generated by fuel combustion, water flow, gas flow, or nuclear fission into mechanical energy that is transmitted to the generator which is then converted to electrical energy.

4. Main Parts of Generator

• Similar to the electric motor, the generator also comes with one rotating part and other stationary parts called rotor and stator respectively.

a. Rotor

• A rotor rotation occurs mainly due to the interaction between the magnetic field and core windings which generates torque around the rotor's axis. The rotor sits inside the stator and is mounted on the motor's shaft.

b. Stator

• The stator is responsible for converting the rotating magnetic field to electric current. The alternator contains both the stator and the rotor and produces electrical voltage.

• The generator regulates the voltage to generate a constant current available for practical use.

c. Armature

• The armature is the primary part of generating power to the external circuit. Armature windings, depending on the design, are located on either stator or rotor, with the field coil covering the other part.

d. Field winding

• The field winding is responsible for generating a rotating magnetic field inside the generator. It is an insulated current-carrying coil on a field magnet that induces a voltage in the armature windings.

e. Split-Ring

• The split-ring, also known as commutator, ascertains that the generated magnetic field is observed by the external circuit.
• It is mainly used to reverse the current direction.
• There is a difference between split-ring and slip-ring. A split-ring commutator reverses the current direction for every half-rotation, whereas a slip-ring is commonly used to maintain a connection between the stationary stator and the spinning rotor.

• The connection between the rotating coil and external circuit reverses each time a half-period of rotation is completed, allowing the metal brush to recalibrate every time the generated electromagnetic field around the coil passes through zero.
• Slip rings are incorporated in DC motors and split-rings are used in generators.

f. Engine

• The generator comes with a separate engine that is mainly used to convert the fuel source into electrical energy.
• Actually, it is responsible for performing the mechanical function in the generator.
• Engines are generally known as the machine’s prime mover where fuel source like propane, bio-diesel, gasoline, diesel, natural gas, water, sewage gas or hydrogen is used to create mechanical energy, which is then converted into electricity.
• Each generator engine is designed to generate a power supply using a certain amount of fuel source.
• The engines commonly used in generators are turbine engines, reciprocating engines, and steam engines.

g. Fuel System

• Generators are mainly composed of a fuel system used to pump and store the required fuel to the generator engine.
• The generator tank is occupied with the fuel to generate the desired power where the fuel pipe is used for connecting the tank to the engine and the return pipe is used for connecting the engine to the fuel tank.
• The fuel filter is connected to the tank for the removal of dust particles before it enters the engine.
• The fuel injector is another part that atomizes the fuel for injecting it directly into the engine combustion chamber.

h. Lubricating System

• The generator components are designed to sustain a certain temperature. A minor increase from the given ratings can cause the generator to explode or the whole system eventually.
• Generators mainly use coolant like a fan or lubricant material to keep the temperature under a certain limit.  The generator generates exhaust as the combustion chamber converts fuel into electricity.
• Generators come with multiple parts where each requires consecutive oiling to ensure proper functioning for a long period.
• The lubricating system is installed for this purpose.

5. Types of Generators

a. Gasoline

• Gasoline generators are mostly used because they are low-cost and gasoline is easily available.
• Gasoline, mind you, becomes short in the areas facing power scarce as they need electricity to run.
• They are an ideal choice for home and commercial purposes because they are small in size and are available in portable models.

• Make sure, these generators are placed in hard to reach places because the fuel used is highly flammable and can damage the surrounding areas.
• Gasoline generators have the ability to generate relatively high emissions compared to biodiesel and diesel fuel generators.
• And they come with less lifespan and less likely to survive in a cold atmosphere due to the highly flammable quality of the gasoline.

b. Emulsified Diesel

• Emulsified diesel is a combination of diesel fuel and water that is commonly blended with a mixing agent.

• These generators produce fewer emissions than ordinary diesel generators, making them more efficient and ideal for working in a rigorous environment.
• Maintaining the required ratio of water with diesel is a little bit tricky and expert professional is needed for their proper maintenance.

c. Bio-Diesel Generator

• Bio-diesel, as the name suggests, runs on fuel made up of a mixture of diesel and another biological source i.e. animal fat or vegetable oil.
• The bio-diesel generator shares the pros and cons of ordinary diesel fuel generators. However, added environmental benefits put them ahead from other generators.
• They burn with less waste and come with lower emission ability, allowing them to utilize less non-renewable energy sources of fossil fuels.

• Although these generators are installed with noisy engines, they are less flammable compared to regular engines.
• These generators are hard to handle due to difficulty in maintaining the diesel to oil ratio in exact proportion i.e. 80:20
• Like diesel generators, they last for two years or less in storage, and they are not readily available.

d. Diesel Fuel

• Like gasoline, diesel is also easily available and comes with the least flammable feature among other fuel sources. Diesel fuel generators are economical and lost longer than gasoline generators.
• They are more efficient and can endure a stern environment if taken care of properly. What makes them stand out is their ability to start easily in a cold environment.
• Diesel generators store the fuel for 24 months and storing larger qualities are not feasible in terms of price. When a power outage occurs, it is almost impossible to pump these generators because they come with quite a high engine emission.
• These generators are not appropriate for wet environments as fuel moisture severely affects the overall performance of the engine residing inside. Regular maintenance is required for these generators and they are less portable for their heavyweight.

e. Natural Gas

• These generators never run out of fuel, because natural gas is readily available almost everywhere. These generators are not portable and come with a heavyweight.
• Natural gas burns smoothly inside the engine, with little to no noise production. They are highly economical and can stand in a cold environment pretty well.
• What comes with affordable unit price, covers up higher installation costs for gas lines.
• These machines don’t last longer compared to diesel generators.
• Stern measures are required while installing the gas lines, as little leakage can cause severe damage.

Applications

• Generators are commonly used for industrial, commercial, and domestic purposes as backup power when the electricity goes down.
• Mini-hydro plants, high-pressure gas streams, wind turbines make use of generators.
• Used in power grid station for electricity generation that is then transferred to the whole city using power grid lines.
• They are used as a standby in events, exhibitions, and converts.
• DC generators, a source of a stable current generator, are used in arc lamps for lighting.