How Does a Generator Work?
Electric generators are a device that converts mechanical energy received from an external source into electrical energy as output. It is important to understand generators do not actually ‘create’ electricals energy. Instead, it uses mechanical energy supplied to it to forces the movement of electric charges in the coil of its winding through an external electrical circuit.
These flows of electric charges constitute the output electric currents supplied by the generator. These mechanisms can be understood by considering a generator similar to a water pump, which causes the flows of waters but does not actually ‘create’ the waters flowing through it.
The modern-day generator work on the principle of electromagnetic inductions discovers by Michaels Faraday in 1831-32. Faraday found that the above flow of electric charges can be induced by moving electrical conductors, such as a wire containing electric charges into a magnetic field.
This movement creates voltages differences between the two ends of a wire or electrical conductor, which in turn causes electrical charges to flow, producing an electric current.
How Do Generators Create Electricity?
Generators don’t actually make electricity. Instead, they convert mechanical or chemicals energy into electricals energy. They do this by capturing the force of motion and forcing electrons from an external source into electrical energy through an electrical circuit.
A generator is essentially an electric motor that works in the opposite direction. Some electric generators, such as those at Hoovers Dam, for example, are huge & provide enormous amounts of energy by transferring the powers created by converting water to turbines into electricity.
Residential and commercials generators, however, are much smaller and rely on more traditional fuels sources such as diesel, gas, and propane to create mechanical power, which can then be forced into a circuit and induce an electric current.
Once electrical current is established, it is directed through copper wires to external power machines, equipment, or entire electricals systems. Modern generators can be attributed to Michaels Faraday’s theory of electromagnetic inductions.
Faradays discovered that when conductors move in magnetic fields, electric charges can be created and directed to creates a flow of current. In its mosts basics form, an electric generator is nothing more than an electromagnet – a wire running near a magnet to direct the flow of electricity. This is similar to how a pump pushes water through a pipe.
Parts of Generator:
The main components parts of a generator can be broadly classified as follows:
The engine is the source of mechanical energy input to the generator. Engine size is directly proportional to the maximums power output that can be supplied by the generator. There are several factories you need to take into accounts when assessing your generator’s engine. The manufacturers of the engines should be consulted to obtains a complete engine operation specification and maintenance schedule.
1.1. Type of Fuel Used
Generators engines operate on a variety of fuels such as gallons of diesel, types of gasoline, propane in liquefy or gaseous form, or natural gas. Smaller engines usually run on gasoline, while larger engines run on diesel, liquid propane, propane gas, or natural gas. Some engines can also operate on a dual feed of both diesel and gas in bi-fuel operation mode.
1.2. Overhead Valve
Overhead Valve (OHV) Engines vs. Non-OHV Engines – OHV engines differ from other engines in that the engine’s intakes & exhaust valves are located in the top of the engine’s cylinders, as opposed to being mounted on the engines blocks. OHV engine has many advantages over other engines such as:
- Compact design
- Simple operation mechanism
- User friendly in operation
- Low noise during operation
- Low emission level
- However, OHV-engine is also more expensive than other engines.
1.3. Cast Iron Sleeve
Cast Iron Sleeve (CIS) in Engines Cylinders – A CIS is a lining in the engine’s cylinder. This minimizes wear and tear and ensures the durability of the engines. Most OHV-engine is equipped with CIS, but it is necessary to check for this feature in the engine of the generator. CIS is not an extensive feature, but it does play an important role in engine durability, especially if your need to uses your generator frequently or for long periods.
The alternator, also known as the ‘zen head,’ is the part of the generator that produces electricity from the mechanical input supplied by the engine. It consists of an assembly of fixed and moving parts enclosed in housing. The components work together to cause relative motion between the magnetic and electric fields, which in turn generates electricity.
This is a fixed component. It consists of a set of electrical conductors wound in coils over an iron core.
2.2. Rotor / Armature
It is the moving component that generates a rotating magnetic field in one of the following three ways:
- By Induction – These are knowns as brushless alternators & are commonly used in large generators.
- By permanent magnets – This is commons in smalls alternators units.
- Using an exciter – An exciters are a smalls source of direct currents (DC) that activates the rotor through a combination of slip rings and brushes.
- The rotor generates a dynamic magnetic field around the stator, which generates a voltage difference between the stator’s windings. It produces the alternating current (AC) output of the generator.
You should keep the following factored in mind when assessing the generator’s alternator:
- Metal versus Plastic Housing – all-metals design ensures the durability of the alternator. The plastic housings tend to deform over time and expose the moving parts of the alternator. This leads to wear and tear, and more importantly, it is dangerous for the user.
- Ball Bearings versus Needles Bearing – Ball bearings are preferred & last longer.
- Brushless Design – An alternator that doesn’t use brushes requires less maintenance and also produces cleaner power.
#3. Fuel System
The fuel tank usually has enough capacity to keep the generator running for an average of 6 to 8 hours. In the case of smaller generator units, the fuel tank is a part of the skid base of the generator or is mounted on top of the generator’s frames.
For commercials applications, it may be necessary to erect & install an external fuel tank. All such establishments are subject to the approval of the Town Planning Division. Clicks on the following links for more information on fuel tanks for generators.
Common features of fuels system include the following:
3.1. Pipe Connection from Fuel Tank to Engine
Supplies line direct fuels from the tank to the engine, and the return line directs the fuel from the engine to the tank.
3.2. Ventilation Pipe for Fuel Tank
The fuel tank has ventilation pipes to prevent pressure or vacuum build-up during tank refilling and drainage. When you refill the fuel tank, be sure to make metal-to-metal contact between the filler nozzle and the fuel tank to avoid sparks.
3.3. Overflow Connection from Fuel Tank to Drain Pipe
These are necessary so that any overflow during refilling of the tank does not result in leakage of liquid on the generator set.
4.4. Fuel Pump
It transfers fuel from the main storage tank to the day tank. The fuel pump is usually electrically operated.
4.5. Fuel Water Separator / Fuel Filter
It separates water and foreign matter from the liquid fuel to protect other components of the generator from corrosion and contamination.
4.6. Fuel Injector
It atomizes the liquid fuel and sprays the required amount of fuel into the combustion chamber of the engine.
#4. Voltage Regulator
As the name implies, this component controls the output voltage of the generator. The mechanisms are described below against each component that plays a role in the cyclic process of voltage regulation.
4.1. Voltages Regulator
Conversion of AC voltages to DC current – voltages regulator takes a small portion of the generator’s outputs of AC voltage & converts it into DC currents. The voltage regulators then feed these DC currents to a set of secondary windings in the stators, known as the exciter winding.
4.2. Exciter Windings
Conversions of DC currents to AC currents – The exciter winding now performs the same function as the primary stator winding and produces a small AC current. The exciter windings are connected to a unit known as rotating rectifiers.
4.3. Rotating Rectifier
Conversion of AC currents to DC current – This rectifies the AC current generates by the exciter winding and converts it into DC current. These DC currents are fed to the rotor/armature to create electromagnetic fields in addition to the rotating magnetic fields of the rotors/armatures.
4.4. Rotor / Armatures
Conversion of DC currents to AC voltages – The rotor/armatures now induce larger AC voltages across the stator windings, which the generator now generates as a larger output AC voltage.
This cycle continues until the generator starts producing an output voltage equal to its full operating capacity.
As the output of the generators increases, the voltage regulator produces less DC current. Once the generators reach full operating capacities, the voltages regulator achieves a state of equilibrium and produces enough DC current to maintain the generator’s output at the full operating levels.
When you add a load to generators, their output voltages drop slightly. This prompts the voltage regulator to function, and the above cycle begins. This cycle continues until the generator output ramps up to its original full operating capacity.
#5. Cooling and Exhaust Systems
5.1. Cooling System
Continuous use of the generator causes its various components to heat up. It is necessary to have a cooling and ventilation system to take back the heat generated in the process. Raw/fresh waters are sometimes used as coolants for generators, but these are mostly limited to specifics situations such as small generators in city applications or very large units of 2250 kW and above.
Hydrogens are sometimes used as coolants for the stators windings of large generators units because it is more efficient at absorbing heats than other coolants. The hydrogen removes heat from the generator and transfers it through a heat exchanger to a secondary cooling circuit that has de-mineralized water as a coolant.
This is why very large generators and smalls power plants often have large cooling towers next to them. For all other common applications, both residential & industrial, a standard radiator and fan are mounted on the generator and serve as the primary cooling system.
It is essential to check the coolant level of the generator on a daily basis. The cooling system and raw water pumps should be flushed after every 600 hours, & the heats exchangers should be cleaned after every 2,400 hours of generators operation.
Generators should be placed in an open ventilated area with an adequate supply of fresh air. The National Electric Code (NEC) states that a minimum of 3 feet of space must be provided on all sides of the generator to ensure the free flow of cold air.
5.2. Exhaust System
The exhaust fumes emitted by a generator are like the exhaust from any other diesel or gasoline engine and contain highly toxic chemicals that need to be managed properly. Therefore, it is necessary to install an adequate exhaust system to dispose of the exhaust gases.
This point cannot be stressed enough as carbon monoxide poisoning is one of the most common causes of death in post-storm areas as people do not even think about it until it is too late.
Exhausts pipes are usually made of cast irons, wrought iron, or steel.
These must be freestanding and not supported by the generator’s engine. Exhaust pipes are usually connected to the engine using flexible connectors to reduce vibration and prevent damage to the generator’s exhaust system. The exhaust pipe terminates outward and leads through doors, windows, and other openings to the home or building.
You should make sure that your generator’s exhaust system is not connected to any other equipment. You should also consult local city ordinances to determine whether your generator operation will require approval from local authorities to ensure you are compliant with local laws and avoid fines and other penalties.
#6. Lubrication System
Since the generator has moving parts in its engine, it requires lubrication to ensure long durability and smooth operation. The engine of the generator is lubricated with oil kept in the pumps. You should check the levels of lubricating oil every 8 hours of operation of the generator.
You should also check for any lubricant leaks and change the lubricating oil every 500 hours of generator operation.
#7. Battery Charger
The steer function of the generator is battery-operated. The battery charger keeps the generator’s battery charged by supplying a precise ‘float’ voltage. If the floats voltage is too low, the batteries will hold less charge. If the float voltages are too high, it will shorten the life of the battery.
Battery chargers are typically made of stainless steel to prevent corrosion. They are also fully automated and do not require any adjustment or change of any setting.
The DC output voltage of the batteries chargers is setting at 2.33 volts per cell, which is the exact float voltage for a lead-acid battery. The battery charger has an isolated DC voltages output which interferes with the normal functioning of the generator.
#8. Control Panel
This is the user interface of the generators & includes provisions for electrical outlets and controls. The following article provides more information about the generator control panel. Different manufacturers have different features to offer in the control panels of their units. Some of these are mentioned below.
8.1. Electric Start and Shut-Down
Auto start controls panels automatically start your generators during power outages, monitor the generator during operation, & automatically shut down the unit when it is not needed.
8.2. Engine Gauge
Various gauges indicate important parameters such as oil pressure, coolant temperature, battery voltage, engine rotation speed, and duration of the operation. Continuous measurement and monitoring of these parameters enable the built-in shutdown of the generator when any of these exceeds their respective threshold level.
8.3. Generator Gauge
The control panel also contains meters for the measurement of output current and voltage, and operating frequency.
8.4. Other Controls
Phase selector switch, frequency switch, & engine control switch manuals mode, auto mode, among others.
#9. Main Assembly / Frame
All generators, portables, or stationary have customized housings that provide structural base support. The frame also allows for generated earthing for safety.