What is a generator?
The basic definition of a generator would be a device that converts mechanical energy into electric energy. This is a technical way of putting things and covers all generators, except a solar generator which works very differently to any conventional means of generating electricity.
Intro | What Is A Generator?
In this article, I’m going to explain what a generator is in a way that is easier to understand. Firstly, we need to look at the most common reference to the term generator. Large power stations, providing the utility power that we use in our homes, businesses, and general infrastructure are not the type generators that we generally speak of. Most people, when we talk about generators, are referring to portable and standby generators. So when someone asks the question “what is a generator?” I’ll assume this what they want to know. These are the types of generators that are commercially available – anyone can go out and buy one. This will be the focus of the article. I’ll start by giving a detailed answer to the question and then break it down into the various types of generators that we’re likely to use in our everyday lives.
With the exception of solar generators (I’ll cover these separately), all generators use an internal combustion engine to drive an alternator. Usually, the engine will use gas as a fuel source, but they can also use diesel or natural gas. These engines are basically smaller versions of the engines that propel our cars, similar to those used in lawnmowers, chainsaws, and other gas-powered machinery.
The alternator is the key component of a generator, this is what produces the alternating current (AC) that we use in our homes. In the US, all generators are designed to produce 120V, 60HZ power, the same power as you get from a regular household electrical outlet. Most large units will generate both 120V and 240V current, so we can use them to run larger appliances and machinery. Many will also have a 12V DC outlet and often USB outlets too. Outside of North America, generators are designed to produce 240V 50HZ current with some also producing 380V, three-phase current. The purpose is to provide us with the same electricity that we would get from the power utility when this is not available.
How does an alternator work?
We now know that the alternator is what provides the actual electricity that we use. But how does an alternator do this? Simply put, an alternator is an electromagnet that produces an electromagnetic field. It is a cylindrical mechanism with a stator running along the inside of this cylinder. The stator is a set of copper windings.
A rotor runs through the center of the stator with a small gap in between them so that the rotor can spin freely. The rotor also has copper windings around a shaft which is connected to the engine. When the engine runs, it spins the rotor at a high speed. This rotation causes the electrons within the copper windings to become energized. An electromagnetic field is created between the rotor and the stator. These charged electrons in the magnetic field are then pulsed between two points, the pulsing electrons are what’s known as an alternating current. The current is then transferred by means of a conductor to the power outlets on the generator.
The amount of power produced by an alternator is measured in watts. Theoretically, there’s no limit to the amount watts that can be produced by a generator. A small alternator, with a small engine driving it will deliver 1000W or less, this will only be capable of providing power for a few small appliances. On the other end of the scale, a nuclear power plant will run several generators, producing megawatts of electricity. These work together with many other generators, all connected to the national power grid. This grid is a sophisticated network of power stations and substations, all controlled by computers to supply constant, stable power to cities, towns and everywhere between them.
However, a portable generator is limited to the size of its alternator and will seldom generate more 15000W of constant power. Standby generators are larger and can deliver up to about 60000W of constant power. The appliances and machinery that we can run off a generator have to fall within the maximum power output of the generator. So, if a generator is rated for 10000W, we cannot exceed this power limit when using the generator.
All portable generators have two power ratings, constant or running watts and peak or startup watts. The constant power rating is the amount of power a generator can produce on a constant basis, we can use the generator to provide power up to the constant running wattage for as long as is needed. Peak power or starting wattage refers to the amount of power that a generator can deliver for a short period of time, this will always be more than the running watts. This peak power rating enables the generator to provide a surge of power for electric equipment that needs an extra boost of power to start. There are many household appliances and machines that use inductive electric motors, this would include refrigerators and air conditioners. Equipment like microwaves and fluorescent lights use ballasts to start. Electric equipment that use capacitors (inductive motors) and ballasts need a higher wattage to start than what they will draw when running.
In order to keep the power output constant, a generator uses a governor. This is a mechanical throttle control that automatically adjusts the engine power to meet the output power demand. A generator needs to run at a constant speed, this is what keeps the output voltage and frequency constant. When the power demand is low, the generator won’t require as much gas to keep it running. As the power demand increases, it will require more gas. The governor controls the ratio between the throttle position and the power output.
This works in the same way as we use the accelerator when driving a car. In order to maintain our speed when we approach an uphill, we will need to press down on the accelerator. If we don’t, the car will slow down. Unlike when driving a car, a generator doesn’t have the benefit of foresight. We can see the incline approaching and will start to accelerate in advance. A generator will only open the throttle once the extra load is added. This means there’s a time lapse between when the load increases and when the engine speed increases. This will cause a momentary drop in voltage. The exact drop in the voltage will depend on the amount of extra power that is required. If a large amount of power is required, the voltage drop will be greater. This causes a distortion in the sine wave and is harmful to electronic equipment.
What is a sine wave?
The pulse generated by an alternating current is represented as a wave, the same as sound waves. We call this a sine wave. The peak of the wave is equal to the voltage and its width is determined by the time (frequency). A change in either the voltage or the frequency will cause the shape of the wave to change. It becomes distorted. We call the distortion of a sine wave Harmonic Distortion (HD). Electronic equipment like computers, TVs, stereos or any device that uses a microprocessor will be damaged if exposed to high levels of HD on a regular basis. The recommended level for the Total Harmonic Distortion (THD) should not exceed 3%. When we discuss inverter generators, you’ll see why this is important.
Sine Wave | Inverter Generator vs Conventional Generator
Types of Generators
The basic principle for all generators remains the same, but there are many different types of generators used for different applications. The generators that we can buy as general consumers fall into three basic categories.
- Portable generators
- Standby generators
- Solar generators
What is a portable generator?
Any generator that can be transported is known as a portable generator. These are the most commonly used generators. A portable generator can be really small and light. Small portable generators, producing around 1000W can be carried in one hand, like a suitcase. Large portable generators, capable of supplying enough power to meet most of our household needs will be too heavy for one person to carry. A large portable generator, producing more than 10000W can weigh in excess of 200-pounds. These large generators will have wheel kits and handles that make it possible to move them about without having to carry them.
The traditional design for a generator is an open frame. This means that the engine and alternator are mounted to a metal frame and are exposed, we can see the mechanical components of the generator. The open frame design is the most cost-effective, but these generators are noisy. The larger a generator becomes, the more noise it will produce.
So there are several drawbacks to conventional generators, the most common of these are noise levels and harmonic distortion. Modern technology has overcome these issues and there are several alternatives to the conventional open frame generator. However, portable generators that use new technology are more expensive.
Using a conventional, open frame portable generator in a residential area or a campsite can be problematic because of their high noise levels. A large portable generator can produce a noise level exceeding 100dBA. To put this into context, a normal speaking voice is about 65dBA. Health safety regulations stipulate that when a noise level exceeds 85dBA, one should wear ear protection when working in close proximity to the source of this noise.
Most generator manufacturers supply silent generators. While no generator is completely silent, the noise that they produce can be significantly reduced. By using improved engine and muffler technology, the noise produced by the engine won’t be as loud as older technology. Furthermore, sound insulated enclosures are used to further reduce the noise level. Silent generators, don’t have an open frame. They look more modern and are sealed within a plastic housing which prevents a lot of the mechanical noise from escaping. A small silent generator will often produce a noise level that is well below 65dBA (quieter than a speaking voice). Even large silent generators, won’t produce a noise level much more than 70dBA. From a distance of about 20-feet away, a generator with a noise level of 70dBA will hardly be noticeable.
These days, just about all of the electrical appliances we use have electronic components. Even an AC or microwave with touch button controls will use a microprocessor. Because of this, there’s a high demand for a generator that produces a clean sine wave with low HD. An inverter is an electronically controlled device that uses capacitors and resistors to convert Direct Current (DC) into Alternating Current (AC).
By making use of an IGBT inverter, it’s possible to ensure that the THD never exceeds 3%. A double conversion system is used in inverter generators. This means that the AC power generated by the alternator is converted into DC and then converted back into AC by the inverter. Because the inverter has computerized management, it’s able to monitor the AC sine wave and adjust it as needed. An inverter will maintain a stable sine wave, regardless of any changes in the power demand.
Another advantage of using inverter technology is the ability to slow the engine revs when the power demand is low. This means it uses less fuel. Many inverter generators also have parallel connection ports. This means that more than one generator can be used – connected in parallel. By connecting two generators in parallel, one is able to double the power output to that of both generators.
Dual Fuel or Hybrid Generators
As environmental awareness has increased, the demand for cleaner burning engines has grown. This has brought about a carburetor that is designed to use both standard gasoline and natural gas (Propane). A dual fuel or hybrid generator is able to use gasoline or propane as a fuel source.
While the initial objective of using propane was for environmental reasons, there are other practical advantages to the user. Propane is safer and easier to store, propane tanks cannot leak and release no fumes like gas cans do. There’s no need to transfer the fuel to a gas tank. A propane tank connects directly to the inlet valve, so there’s no chance of fuel spillage. Propane can be stored indefinitely, whereas gas deteriorates over time. Because propane is stored in a compressed state, it has a lower volume. This means that one can store a greater amount of fuel in a smaller tank, making propane much more practical in that you don’t need to transport a large volume of fuel.
What is a standby generator?
The basic operation of a standby generator is similar to that of a portable generator. It uses a gas or propane-fueled engine to drive an alternator, providing AC power that we can use in our homes or businesses. The most notable difference is that a standby generator is much larger and produces more power, enough to run an entire house. Large standby generators will produce enough power to supply a shopping mall, factory, or apartment complex.
Standby generators for the home are readily available and typically supply anything from 15KW up to 60KW. They also make use of an automatic transfer switch, meaning that the user doesn’t have to start the generator or switch over the power supply. When the utility power fails, the automatic transfer switch will start the generator and transfer the power supply from the utility power to the generator. When the main power supply is restored, the transfer switch will automatically restore the power supply to the utility power and stop the generator.
Because these generators are larger than portable generators, they are obviously more expensive. The fact that they use an automatic transfer switch and have weatherproof enclosures, further increases their cost. A standby generator has to be installed by a professional in accordance with local electrical codes and this is an additional expense. All these cost factors make standby generators less common.
Despite their cost, there are several advantages to using a standby generator. The most obvious being that they produce enough power to run the entire household without compromise. A standby generator is also installed far from the house, so there are no noise issues. The automatic transfer switch makes them much more convenient than a portable generator that needs to be started and connected to the house power manually. The user only has to ensure that the generator has enough gas and that it is serviced by a professional at regular intervals. Standby generators have large gas tanks and seldom need refueling.
What is a solar generator?
Technically, a solar generator is not a generator in the conventional sense of the word. The correct term for a solar generator is a hybrid inverter, though the most common term is a solar generator.
As the name suggests, these generators use solar panels rather than an engine, like other generators. Solar panels generate direct current using the sun’s energy in a process known as photovoltaics. The electricity is then stored in a battery (or batteries) to be used whenever needed. When it’s not possible to use solar energy, the batteries can be charged by the mains power. You can plug a solar generator into a 120V outlet to charge the batteries.
Solar Generator | Renogy Phoenix — All-in-one Solar Kit
There are several advantages to using a solar generator. Because they don’t have an engine, solar generators are virtually silent. Apart from the noise of cooling fans, one hardly hears them running. Another advantage of not using an engine is that a solar generator produces no toxic fumes. This means that a solar generator can be placed indoors, right where you use them. They are safe and there’s no noise to contend with.
One of the disadvantages of a solar generator is the initial purchase price. In order to generate enough power, one needs several solar panels and several batteries are required to store enough power to use when the sun is not shining. Though, once you’ve paid for the generator, panels, and batteries, your power is basically free. There’s also no need to keep gas and a solar generator requires no regular maintenance. Over time, the price of the solar generator is absorbed by its low running cost. The fact that they use an inverter also means that one has clean low HD power, like using an inverter generator.
Another disadvantage of using a solar generator is the limited battery storage and power output of the generator. Even when using several batteries, one is still limited to the amount of power that can be stored in these batteries. When the batteries run flat they need to be recharged and this takes time. Furthermore, portable solar generators seldom produce more than 2000W, so one is limited as to which appliances you run off the generators. A solar generator that produces 5kw or more will be too large to be portable, they will also require a lot of batteries and solar panels.