How Generators Work

Electrical generators are standalone machines that provide electricity when power from the local grid is unavailable. Industrial generators are often used to supply backup power to facilities, businesses, or homes during power outages but they can also be used as a primary power source in areas where a local electrical grid is unavailable or difficult to access such as mining and farming operations or even new developments and construction.

It’s possible to buy a generator for just about any need. Some electrical generators are small, portable devices that are used for camping or hobbies to provide small amounts of power for just a few devices. Others are permanent installations that can power an entire house. Industrial generators are even more powerful, capable of maintaining full power to manufacturing facilities, hospitals, and office complexes.

There are diesel generators, natural gas generators, propane generators, and bi-fuel generators. Below, we’ll take a look at how electrical generators work and what you need to know to install and maintain a generator.

How Do Generators Create Electricity?

Generators don’t actually create electricity. Instead, they convert mechanical or chemical energy into electrical energy. They do this by capturing the power of motion and turning it into electrical energy by forcing electrons from the external source through an electrical circuit. A generator is essentially an electrical motor working in reverse.

Some electrical generators, such as those at Hoover Dam, for example, are huge and provide enormous amounts of energy by transferring the power created by water turning turbines into electricity. Residential and commercial generators, however, are much smaller and rely on more traditional fuel sources like diesel, gas, and propane to create mechanical power that can then be forced into a circuit and induce an electrical current.

Once an electrical current has been established, it is directed through copper wires to power external machines, devices, or entire electrical systems.

Modern generators can be attributed to Michael Faraday’s principle of electromagnetic induction. Faraday discovered that when a conductor moves in a magnetic field, electrical charges could be created and directed to create a flow of current. At its most basic, an electrical generator is nothing more than an electromagnet – moving wire near a magnet to direct the flow of electricity. It’s similar to how a pump pushes water through a pipe.

What Are The Parts Of An Electrical Generator?

There are nine parts to a generator and they all play a role in getting power to where it is needed most. The parts of a generator are:

1. Engine. The engine supplies energy to the generator. The power of the engine determines how much electricity a generator can provide.

1. Alternator. This is where the conversion from mechanical energy to electrical energy occurs. Also called a “genhead”, the alternator contains both moving and stationary parts that work together to create the electromagnetic field and movement of electrons that generates electricity.

1. Fuel System. The fuel system makes it possible for the generator to produce the energy needed. The system includes a fuel tank, a fuel pump, a pipe connecting the tank to the engine, and a return pipe. A fuel filter removes debris before it gets to the engine and an injector forces the fuel into the combustion chamber.

1. Voltage Regulator. This component helps control the voltage of the electricity that is produced. It also helps convert the electricity from AC to DC, if needed.

1. Cooling and Exhaust Systems. Generators create a lot of heat. The cooling system ensures the machine doesn’t overheat. The exhaust system direct and remove the fumes the form during operation.

1. Lubrication System. There are many small, moving parts inside a generator. It is essential to lubricate them adequately with engine oil to ensure smooth operation and protect them from excess wear. Lubricant levels should be checked regularly, as often as every 8 hours of operation.

1. Battery Charger. Batteries are used to start up the generator. The battery charger is a fully automatic component that ensures the battery is ready to go when needed by supplying it with a constant low-level of voltage.

1. Control Panel. The control panel controls every aspect of generator operation from start up and running speed to outputs. Modern units are even capable of sensing when power dips or goes out and can start or shut off the generator automatically.

1. Main Assembly / Frame. This is the body of the generator. It is the part that we see; the structure that holds it all in place.

What Kind Of Fuel Do Electrical Generators Need?

Today’s electrical generators are available in many different fueling options. Diesel generators are the most popular industrial generators on the market. Residential generators more commonly include: natural gas generators or propane generators, while the smaller portable generators typically run on gasoline, diesel fuel, or propane. Some generators are bi-fuel capable – running on both gasoline and diesel.

Generator Fuel Tanks

The fuel system ensures the generator has the necessary raw materials needed to provide electricity by initiating the internal combustion process. Without fuel, combustion can’t take place and the generator can’t convert the mechanical energy created into electrical energy. Generator fuel needs to be stored on-site so the generator can be put into operation immediately when necessary.

Depending on the type of generator and its application, fuel tanks may be mounted to the generator frame or they may be external tanks located far from the actual generator. In general, the bigger the generator and the longer it needs to run, the bigger the fuel tank. Generator fuel is stored in tanks of various capacities, depending on the intended use of the generator and the amount of power required. Tanks my be located above ground, below ground, or sub base. Sub base tanks are intended for storing less than 1,000 gallons of fuel and are located above ground, but below the base of the generator set.

Above ground and below ground generator fuel storage tanks are a better choice for high capacity needs. Underground storage tanks are more expensive to install, but they tend to last longer since they are protected from the elements. There are pros and cons to both types of fuel storage tanks but you won’t be alone in making a decision. Generator fuel tanks and generator fuel systems must meet several code requirements and approvals before they can be installed, whether the installation is for residential or commercial use.

The primary code governing generator fuel tanks in the United States is the National Fire Protection Association Codes and Standards (NFPA), particularly sections NFPA 30 and NFPA 37. As such, all requests for a generator fuel tank must be submitted to the State Fire Marshall for approval.

To determine your minimum fuel tank capacity needs, you’ll need to think about how you intend to use the generator. For short or infrequent power outages, a backup generator with a smaller storage tank may be acceptable, however you’ll need to refill the tank more frequently than you’d have to refill larger tanks. Larger storage tanks may be required if you’re planning to power a large commercial facility with a prime generator or if you are subject to long, frequent power outages.

Your generator supplier can help you determine the optimal fuel tank size to ensure you have enough fuel on hand when you need it. One more thing to keep in mind both when buying a generator and selecting a generator fuel storage tank is the cost and availability of the fuels to your location. It’s a good idea to talk to local fuel suppliers before you buy a generator to get a better idea of the cost and logistics involved in obtaining generator fuel.

Generator Exhaust Systems and Emissions Controls

As machines that burn fossil fuels and run continuously, even if that run time is erratic, generators must be equipped with components to cool them off and to filter emissions. Generator cooling and ventilation systems reduce and remove heat in a variety of ways:

• Water. Water can be used to cool off generator components. This type of coolant system is typically limited to specific situations or very large units of 2,250 kW and higher.

• Hydrogen. Hydrogen is a very efficient coolant that is used to absorb heat given off by a running generator. The heat is transferred to a heat exchanger and a secondary cooling circuit, often located in large, on-site cooling towers.

• Radiators and fans. Smaller generators are cooled through a combination of a standard radiator and fan.

The fumes emitted by generators are just like the exhaust given off by other gas or diesel powered engines. They include toxic chemicals, like carbon dioxide, which must be filtered and removed from emissions. The generator exhaust system manages this task.

Exhaust pipes are connected to the engine where they direct fumes up, out, and away from the generator and the facility. The pipe extends outside the building housing the generator and should terminate far away from doors, windows, and other areas of air intake.

In addition to exhaust systems, some generators are subject to federal emission controls. The generator emissions monitored are: Nitrogen Oxide (NOx), Hydrocarbons, Carbon Monoxide (CO), and Particulate Matter.

In general, emergency generators and generators that run for less than 100 hours per year are not subject to federal generator emissions requirements, however, permanently installed prime generators and standby generators are subject to federal emissions requirements under three EPA rules:

• National Emission Standard for Hazardous Air Pollutants (NESHAP) – For Reciprocating Internal Combustion Engines (RICE). 40 Code of Federal Regulations Part 63, Subpart ZZZZ. Also known as the RICE rule.

• New Source Performance Standards (NSPS) – Standards of performance for stationary spark ignition engines. 40 CFR, Part 60, Subpart JJJJ. Also known as the spark ignition NSPS rule.

• Standards of Performance for Stationary Compression Ignition Internal Combustion Engines. 40 CFR, Part 60, Subpart IIII. Also known as the compression Ignition NSPS rule.

The good news is that many newer gensets already meet generator emissions standards thanks to manufacturing improvements. Older gensets may be grandfathered in, making them exempt from federal regulations, and subject only to state and local emissions standards. Emissions control requirements vary by manufacturer, generator size, and production date so the best way to determine your emissions requirements is to talk to your generator dealer or manufacturer.

For a deeper look at emission regulations, read this white paper from Cummins, “The Impact of Tier 4 Emission Regulations on the Power Generation Industry”. 

The Generator Control Panel And Automatic Transfer Switch (ATS)

One of the most important components of modern-day generators is the generator control panel. The control panel is the brains of the generator and is also the user interface of the generator; the point at which you’ll access and control generator operation.

Many control panels feature an Automatic Transfer Switch (ATS), which continuously monitors incoming power. When the power level drops or cuts out entirely, the ATS signals the control panel to start up the generator. Likewise, when incoming power is restored, the ATS signals the control panel to shut the generator down and reconnects to power grid.

In addition to 24/7 monitoring, the generator control panel provides a wealth of information for site managers:

• Engine gauges provide important information about oil and fluid levels, battery voltage, engine speed, and operational hours. In many gensets, the panel will even automatically shut down the engine when it detects a problem with fluid levels or other aspects of generator operation.

• Generator gauges provide valuable information about output current, voltage, and operating frequency.

What Kind of Maintenance Does A Generator Require?

Generators are engines and require routine engine maintenance to ensure proper operation. Since many generators are relied on to provide back-up power in the event of emergencies, it is crucial for operators to conduct regular checks and inspections of their gensets to ensure the machine will operate as needed, when needed.

The best generator maintenance routine is the one recommended by the manufacturer, but, at a minimum, all generator maintenance plans should include regular and routine:

• Inspection and removal of worn parts.
• Checking of fluid levels, including coolant and fuel.
• Inspection and cleaning of the battery.
• Conducting of a load bank test on the generator and automatic transfer switch.
• Checking of the control panel to ensure accuracy of readings and indicators.
• Changing of the air and fuel filters.
• Inspection of the cooling system.
• Lubrication of parts as needed.

Be sure to maintain a maintenance log for recordkeeping. Include all readings, fluid levels, etc. along with the date and the hour meter reading of the generator. These records can be compared against future records and used to help detect abnormalities or changes in operation which may clue you in to hidden issues that could become major problems if left unchecked.

Generators can last for decades when properly maintained. These simple, small investments will definitely pay off over time by saving on expensive repairs or even full genset replacement. If generator maintenance isn’t something you can manage in-house, many generator dealers offer maintenance contracts or can recommend qualified maintenance technicians to help you keep your generator in tip-top shape year after year after year. It’s time and money well spent if it can keep your business up and running when the power goes out.

How Do I Size A Generator?

The single most important part of installing a backup generator or a prime generator is getting the size right. Undersized generators won’t be able to provide you with all the power you need and you’ll be forced to pick and choose which electrical components will receive power from the generator and which ones won’t. Even worse, running an undersized machine can strain the unit, causing the generator to cut out mid-operation, may lead to premature generator failure, and can possibly damaging the devices connected to it.

Some think that it’s acceptable to install a smaller than needed standby generator since it won’t be running all the time, but this is faulty logic because when a standby generator is needed it must power the entire facility. In other words, you still require the generator to provide a certain amount of power whether the generator is run continuously or only on an emergency basis.

It’s generally better to buy a bigger generator than a smaller one, but oversized generators have their drawbacks as well. Installing a generator that provides much more power than you need is a waste of resources. You’ll overspend on the genset itself, spend more on fuel and other consumables than you need, and also run the risk of damaging the devices connected to the generator.

Generators range in power capacity from 5 kW to 50 kW in the residential market and from 50 kW to over 3 Megawatts in the commercial and industrial markets, giving buyers plenty of choices, but also raising plenty of questions as to which generator is right for them. Correctly sizing a generator involves several factors and considerations. The best way to ensure you have sized the generator correctly is to consult a certified electrician. An electrician can determine your exact power needs, your electrical system capacity and any necessary upgrades, and how to best install a generator.

Still, you can get an idea of your power needs yourself by:

• Creating a list of everything that needs to be powered by the generator.

• Noting the starting and running wattage of each of those items. You can find this information on the device’s identification plate or the owner’s manual.

• Calculating the total power requirements in kVA or kW. Some devices will provide power requirements in amps. You’ll need to convert amps to kW or kVA to determine power demands. Use this power calculator to create your conversions.

Once you have the total power requirements of facility, you can buy a generator that best meets your needs. Used and surplus generators are a great way to save money and still get a quality machine. Since generators are so durable and long-lasting, even well-maintained used generators have a lot of life left in them. Reputable generator suppliers will have checked the unit over for issues and reviewed the maintenance log and possibly even have made necessary repairs before they put the generator up for sale. As long as you have a maintenance record and know the history of the generator, there is no reason to shy away from used generators. Surplus generators offer similar benefits but without any or with very few running hours on the machine. 

Where Can I Buy A Generator?

There are many generator suppliers in the U.S. from home improvement stores to generator manufacturers themselves. If you plan to buy a generator as a business asset and a way to keep your doors open during an emergency, take your time and work with a dealer, broker, or supplier that has many years of experience. Find a seller who can answer your questions, assess your situation, and guide you to the best purchasing decision based on your specific needs.

Critical Power Products & Services’ team has over 25 years of experience in the acquisition and disposal of industrial power equipment, including generators. We sell used generators and surplus generators that have undergone a rigorous inspection and testing to small businesses and Fortune 500 companies alike all across the U.S.

To learn more about our services and inventory or call us at 1-877-879-8917 to discuss your needs with one of our project managers. We’re certain we can help you account for every consideration in your generator purchase and match you up with the perfect machine for the job!