Generator working principle: Everything you need to know

generator by the river
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    A generator is a useful device to provide power during a power outage and prevent interruption of daily activities or business operations. Generators come in different electrical and physical configurations and can be used for various applications. In the following sections, we will learn how generators work, the main components of generators, and how generators operate as auxiliary power sources in residential and industrial applications.

    How does a generator work?

    A generator is a device/machine that produces electrical energy using mechanical energy from an external source. 

    It’s important to understand that generators don’t actually “produce” electricity. Instead, it drives the charge in its winding wires through an external circuit using the mechanical energy given to it. This flow of charge constitutes the output current provided by the generator. By comparing a generator with a water pump, which creates water flow but does not truly “make” the water that passes through it, we may better grasp this mechanism. 

    Modern generators work on the principle of electromagnetic induction discovered by Michael Faraday in 1831-32. Faraday found that the charge flow mentioned above could be induced by moving electrical conductors in a magnetic field. The conductors can be wires containing charges. This movement creates a voltage difference between the ends of the wire or electrical conductor, which causes electric charge to flow, creating an electrical current.

    worker checking instrument

    components of a generator

    the main parts of an electric generator can generally be classified as follows:

    1. Engine
    2. Alternator
    3. Fuel System
    4. Voltage Regulator
    5. Cooling and Exhaust Systems
    6. Lubrication System
    7. Battery Charger
    8. Control Panel
    9. Main Assembly / Frame

    Let’s see the purpose of each of the components mentioned above. 

    1) Engine

    The engine is the source of input mechanical energy to the generator. The size of the engine is proportional to the maximum power output the generator can provide. It will help to keep several factors in mind when evaluating a generator’s engine. One should consult the engine manufacturer for a complete engine operating specification and maintenance schedule.

    Type of fuel

    Generator engines use various fuels such as diesel, gasoline, propane, or natural gas. Smaller engines typically run on gasoline, while larger engines run on diesel, liquid propane, propane gas, or natural gas. Some engines can also run on a dual supply of diesel and natural gas in a dual fuel mode of operation.

    generator on grass
    Overhead valve (OHV)
    Overhead valve (OHV) engines vs. non-overhead valve engines

    Overhead Valve (OHV) engines differ from other engines in that the engine’s intake and exhaust valves are located on the engine cylinder head instead of Installed on the engine block. Compared to other engines, OHV engines have several advantages, such as:

    • compact design
    • Simpler operating mechanism
    • Durability
    • User-friendly operation
    • Low noise during operation
    • Low emission levels

    However, OHV engines are also on the pricier side than other engines.

    Cast iron sleeve (CIS) in the engine cylinder

    The CIS is the lining in the engine cylinder. It reduces wear and ensures the durability of the engine. Most overhead valve (OHV) engines have a cast iron sleeve (CIS), but you must check this feature. Even though CIS is a very inexpensive feature, it is crucial for engine durability, mainly if you operate the generator frequently or for extended periods. 

    Cast iron sleeve (CIS)

    2) Alternator

    An alternator(AC generator) also called a “genhead,” is the part of a generator that produces electrical output from the mechanical input provided by the engine. It contains an assembly of fixed and moving parts enclosed in an enclosure. These components cause relative motion between the magnetic and electric fields, generating electricity.

    1. a) Stator – This is the component that remains stationary. It consists of a set of electric conductors in coils wound around an iron core.
    2. b) Rotor/armature—this is the moving part that produces a rotating magnetic field in any of the following three ways:
    3. i) Induction – These are called brushless alternators and are typically used in larger generators.
    4. ii) via permanent magnets – this is common in small alternators.

    iii) Use of an exciter – An exciter is a small direct current (DC) power source that powers the rotor through an assembly of conductive slip brushes and rings.

    A voltage difference between the stator windings results from the rotor’s creation of a rotating magnetic field that surrounds the stator. This produces the output of the generator, the alternating current(AC).


    Here are the factors you need to keep in mind when evaluating a generator alternator:

    (a) Metal housing vs. plastic housing – The all-metal design ensures the durability of the alternator. The plastic casing deforms over time and exposes the moving parts of the alternator. These increases wear and tear and, more importantly, are detrimental to the user.

    (b) Ball Bearings vs. needle Bearings – Ball bearings are the first choice and will last longer.

    (c) Brushless Design – Alternators that do not use brushes require less maintenance and produce cleaner electricity.

    generator parts

    3) Voltage regulator

    This part controls the generator’s output voltage, as its name implies. The mechanism is described below for each component that functions during the cycling of voltage regulation.

    a) Voltage Regulator

    It converts AC Voltage to DC Current – The voltage regulator takes a small fraction of the generator’s output AC voltage and converts it to DC current. The voltage regulator feeds this DC current to a set of secondary windings in the stator, called the exciter windings.

    b) Exciter winding

    They convert DC Current to AC Current. The exciter winding now functions like the primary stator winding and produces a small AC current. The exciter winding is connected to a unit called a rotating rectifier.

    c) Rotary rectifiers

    They convert AC Current to DC Current. These rectifiers rectify the AC current produced by the exciter winding and convert it to DC. In addition to the rotor/armature’s rotating magnetic field, this direct current is transmitted to the rotor/armature to generate an electromagnetic field.

    d) Rotor/Armature

    It converts DC Current to AC Voltage – The rotor/armature now induces a larger AC voltage on the stator windings, and the generator produces a larger output AC voltage.

    This cycle continues until the generator produces an output voltage equivalent to its total operating capacity. As the generator output increases, the DC current produced by the voltage regulator decreases. Once the generator reaches total operating capacity, the voltage regulator reaches equilibrium and produces enough DC current to maintain the generator’s output at total operating levels.

    When you add load to the generator, its output voltage drops slightly. This causes the voltage regulator to kick in, and the cycle described above begins. The process continues until the generator output rises to its original total operating capacity.


    4) Cooling and exhaust system

    (a) Cooling system

    Continued use of a generator can cause its various components to heat up. There must be a cooling and ventilation system to remove the heat generated.

    Raw/fresh water from rivers or sea is sometimes used as a coolant for generators. Still, these are mostly limited to specific situations, such as small generators in urban applications or massive units exceeding 2250 kW and more. 

    For the stator windings of large generators, hydrogen is sometimes used as a coolant because it absorbs heat more efficiently than any other coolant. The hydrogen removes heat from the generator and sends it to a secondary cooling circuit with deionized water as a coolant via a heat exchanger. This explains why sizable cooling towers are frequently located near enormous generators and small power facilities. For all other typical applications, including residential and industrial, standard radiators and fans are mounted on the generator and used as the primary cooling system.

    The coolant level of the generator must be checked daily. Every 600 hours of generator operation, the cooling system, and raw water pump should be cleansed, and every 2,400 hours, the heat exchanger should be cleaned. The location of generators should be open, well-ventilated, and with a sufficient supply of fresh air. The National Electrical Code (NEC) stipulates that the generator must have a minimum of 3 feet of clearance on all sides to permit the free circulation of cooling air. 

    b) Exhaust system

    Exhaust gas from generators, like any other diesel or gasoline engine exhaust, contains highly toxic chemicals that must be adequately managed. Therefore, an adequate exhaust system must be installed to handle the exhaust gas. This point cannot be overemphasized, as carbon monoxide poisoning remains one of the most common causes of death in post-hurricane-affected areas because people tend to think about it when it’s too late.

    Typically, steel, wrought iron, or cast iron are used to make exhaust pipes. These need to be independent and should not be supported by the generator’s engine. The exhaust pipe is usually attached to the engine using a flexible connector to minimize vibration and avoid damage to the generator’s exhaust system. Exhaust pipes terminate outdoors and lead away from the house or building’s doors, windows, and other openings. You must ensure that the generator’s exhaust system is not connected to the exhaust system of any other equipment. You should also consult your local city ordinance to determine if your generator operation requires approval from local authorities to ensure you are complying with local laws to prevent fines and other penalties.

    Lubrication system

    5) Lubrication system

    Because generators contain moving parts in their engines, lubrication is required to ensure long-term durability and smooth operation. The engine of the generator is lubricated by oil stored in the pump. You should check the oil level every 8 hours of operation. Every 500 hours that the generator is operating, you should also replace the oil and check for lubricant leaks. 

    6) Battery charger

    The battery powers the starting function of the generator. By giving it a precise “float” voltage, the battery charger maintains the generator battery’s charge. Battery undercharge will persist if the float voltage is very low.

    The battery’s lifespan will be shortened if the float voltage is high. 

    In order to avoid corrosion, battery chargers are typically built of stainless steel. They are also fully automatic, requiring no adjustments or changing any settings. The DC output voltage of the battery charger is set to 2.33 volts per cell, which is the exact float voltage for lead-acid batteries. The isolated DC voltage output of the battery charger can obstruct the generator’s normal operation. 

    7) Control panel

    The Control panel is the generator’s user interface, which includes the power outlet and controls. Different manufacturers offer different functions in the control panel of their devices. Some of them are mentioned below.

    a) Electric start and shutdown

    The Auto Start control panel automatically starts the generator during a power outage, monitors the generator while it is running, and automatically shuts down the unit when it is no longer needed.

    b) Engine gauges

    Important data, including oil pressure, coolant temperature, battery voltage, engine speed, and run duration, may all be seen on several gauges. Continuous measurement and monitoring of these parameters allow the built-in shutdown of the generator if any of them exceed their respective threshold levels.

    c) Generator gauges

    The control panel also has meters for measuring output current, voltage, and operating frequency.

    d) Other controls

    Phase selector switches, frequency switches, engine control switches, etc.

    8) Main assembly/frame

    All generators, whether portable or stationary, have custom enclosures that support the structural foundation. For safety, the frame also allows the generated to be grounded.

    Applications of generators

    Generator applications include the following.

    • In different cities, generators provide electricity to most of the electricity network.
    • Used in transportation 
    • Small generators provide excellent backup power for home and business power needs.
    • Used to drive the motor
    • Used before power is set up at the construction site.
    • Used in the lab to give the range of voltage


    So, there you have it; that’s how generators work. The engine provides mechanical energy to the alternator, which is then converted into electrical current by a magnetic field that produces electromagnetic induction. However, now you know exactly how this happens and all the different parts inside the generator.

    For more information or to discuss your power requirements with the BISON team of experts, please call (+86) 13088619098 or email [email protected].

    Generator working principle FAQ

    Propane engines are very similar to gasoline engines in that they both operate on the principle of spark ignition. A propane engine injects a mixture of air and fuel into the engine cylinders, where a spark plug ignites the mixture.

    Propane has several advantages that make propane generators suitable for residential backup power applications. Both gasoline and diesel go bad after a few years, and having a can of both fuels in the house can produce fumes. Gasoline and diesel can also be spilled, which will make cleanup difficult. In contrast, propane can be stored indefinitely with no risk of spillage. Importantly, there's no need to keep an additional fuel tank in the house because many homeowners already have a propane cylinder on hand. 

    standby generators are designed to take power to the site in the event of a power failure until power is restored. hospitals, data centers, government buildings, offices, and many other buildings require backup/standby generators to maintain critical services during these conditions. in addition, non-critical services such as hotel lighting and air conditioning also require power in the event of a power outage. depending on how crucial the application is, standby generators must be operational in a matter of seconds to minutes. they are created for quick, powerful startups and for limited use.

    generators powered by natural gas and propane are fairly similar. both need spark plugs, and both have clean emission curves. using natural gas is generally only feasible where there is a natural gas distribution network service, and self-storage is rarely an option. this is mostly not the case in rural areas.

    natural gas generators are ideal for commercial and industrial applications with a reliable supply of natural gas. natural gas tends to be very cheap and widely available. also, because natural gas burns so cleanly, the environmental regulations for natural gas generators tend to be much less restrictive than those that apply to liquid fuel generators, so they can sometimes be used more flexibly than diesel or gasoline generators.

    although home generators are smaller than those used in commercial and industrial settings, they function similarly and have similar parts. the best and simplest way to install a home generator is to connect it to the main electrical panel in your home so it can power all the circuits in your home when needed. this is done with a device called a transfer switch. the transfer switch prevents power from being transferred from the generator to the power line, so utility workers don't risk being electrocuted by someone's home generator while working on the line.

    most homes use generators for backup power. in case of a power outage, the generator senses the outage and starts automatically, usually within seconds.

    a scaled-down version of a home generator, a portable generator has an engine that is around half the size of a lawnmower engine. there are numerous portable generators that weigh 50 pounds or less. their portability makes them ideal for camping trips, picnics, and construction projects.

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