Lumens and Footcandles. We’ll show you how to choose the correct light bulb when switching out an old incandescent bulb, we’ll explain lumens, footcandles and Lux for those using the metric system. We’ll show you how footcandles change with the square of the distance, and how to calculate foot candles.
If you prefer to watch the YouTube version of this presentation, scroll to the bottom.
Replacing Light Bulbs – Buy the Lumens, Not the Watts
It used to be easy to switch out incandescent light bulbs based on how many watts they used, because all you had to do was go to the store and pickup one that matched the watts. With the need for increased energy efficiency and the increased use of LED lights, this doesn’t work anymore.
The latest bulbs use up to 80% less power to give you the same amount of light. Switching from incandescent to LED using the same watts doesn’t work. It’s the lumens that you want to match. Buy the Lumens, not the watts. The higher the lumens, the brighter the light.
Match the Lumens of your Old Incandescent with the Lumens of a new Energy Efficient light
When changing from incandescent to LED or other energy saving bulb, it’s the lumens that represents the brightness, not the wattage. If you maintain the same distance from the light bulb to the floor or task area, then getting the equivalent lumens should work.
Here is a rule of thumb from the government energy savers program.
When replacing an incandescent bulb
Replace a 100-watt incandescent bulb with a light bulb that provides about 1,600 Lumens.
Replace a 75-watt light bulb, with one that provides about 1,100 lumens.
Replace a 60-watt light bulb, with one that provides about 800 lumens.
And replace a 40-watt light bulb, with a light bulb that provides about 450 lumens.
Replacing incandescent light bulbs with equivalent in Lumens, not watts
Lighting Facts Label
When shopping for light bulbs, look at the label on the package and you should see the lumens listed as shown here.
Lighting Facts Label on all Light Bulb Packages
The label will provide you with the lumens, the estimated savings based on an assumption of your cost per kw, the projected life of the bulb based on daily hours used, the appearance of the light from a warm yellowish color to a cooler blue appearance, and the energy consumed in watts.
What is a Footcandle?
A footcandle is defined as a measurement of the light’s intensity. One foot candle equals the amount of light to saturate a one-foot square with one lumen of light.
Footcandle.
What this means is that the number of lumens produced by the light source, whether that’s an office light fixture or a lamp at home is measured not by how many lumens leave the bulb, but by how many reach the surface being measured and it’s expressed in foot candles.
Footcandles would tell us how much of the light that leaves the fixture arrives at the surface where it’s needed.
Why use Footcandles
Using footcandles allows different sources of light to be compared and provide a standard that can be measured. Footcandles are directly affected by the distance from the source of lumens and can be expressed in a simple formula.
Footcandles = Lumens/ (Distance in Feet)2
This makes the distance from the source a main factor, and the distance works inversely with the footcandles.
If you had a 10-Watt LED light with 800 Lumens, then you could figure your footcandles using the formula starting with the lamp 1 foot off the floor we get
Footcandles = 800 Lumens / (1 foot) 2
Footcandles = 800 / 1 = 800 Footcandles.
The lumens and the footcandles match as the distance is only 1 foot.
Moving the lamp to 4 feet above the floor we now get
Footcandles = 800 Lumens / (4 feet) 2
Footcandles = 800 Lumens / (16) = 50 FC
Again, this time at 8 feet above the floor we get
Footcandles = 800 Lumens / (8 Feet) 2
Footcandles = 800/64 = 12.5 FC
Using that same 10-watt LED light, but hanging it at 10 feet, instead of 8, the footcandles or amount of useful light changes at the surface.
Footcandles = 800 Lumens / (10 feet) 2
Footcandles = 800/100 = 8 FC
This clearly shows the relationship between distance and footcandles, and that the lumens can remain the same but have very different results based on height.
Footcandles and the effects of distance.
This is common sense to all of us, but this formula makes it easy to calculate the affect and gives illuminating engineers something to use in laying out the lighting design to ensure proper lighting for the various areas of the building.
We can see that if the distance is only 1 foot, then our lumens will equal our footcandles as that is the definition.
What does the IES Recommend?
The IES, or better known as the Illuminating Engineering Society provides a standard for lighting levels for various surfaces, such as the following: Operating room 1,000 Footcandles. This is definitely important because the medical staff needs to see clearly. Classrooms 100 footcandles, Gymnasium 100, offices 50, factory floor 30, hallways 10 and a parking lot only 2 footcandles.
IES Requirements for Footcandles based on space type
For anyone trying to read in a parking lot at night, now you know why its difficult, because they’re only designing to achieve a few footcandles of light.
LUX and the Metric System
For those using the metric system, this would be expressed in LUX. One footcandle is equal to 10.764 Lux.
Lumens expressed in SI Units of Lux per square meter
Remember that our formula for footcandles was based on 1 square foot. Since a square meter has 10.764 square feet, then we need to multiply our footcandles by 10.764 to get the equivalent footcandles/m2.
Lumens expressed in IP and SI units. (Footcandles and Lux)
It’s the same amount of footcandles, it’s just expressed for a larger area, because instead of 1 square foot, we are using 10.764 square feet or 1 square meter.
Data Center HVAC Systems. Data centers have HVAC Cooling Systems that differ from your standard air conditioning system because they cool information technology equipment (ITE), instead of people. This IT equipment requires much more cooling than a room full of people. The average person sitting gives off 400 to 450 Btu/hour, while one rack of IT Equipment can give off between 17,060 Btu/hour (5 kw) to 102,360 Btu/hour (30 kw). Data centers are energy intensive, and are growing more so.
If you prefer to watch the FREE YouTube Video of this then scroll to the bottom of the page.
Heat produced by Air-Cooled and Liquid Cooled IT Equipment Racks
We’ll explain the various HVAC systems that serve Data Centers, including air-cooled and liquid-cooled IT equipment. We’ll explain the three most popular data center system strategies, such as room, aisle, or in-row cooling. You’ll learn about proper air management in Air-Cooled systems.
With the explosion in growth of the web and social media, the farming of cryptocurrency and online commerce, data centers are in demand to hold all the data that supports these online activities.
Data centers never shut down which is a huge drain on energy, as these facilities run 24 hours a day, 7 days a week, 365 days a year, never taking a break. All those servers and support equipment running continuously causes a large heat load that needs to be removed from the IT Equipment to function optimally.
Racking
All the IT equipment sits on shelfs arranged vertically in a rack. The standard rack height is 7 feet (2.1m). These racks lined up together in neat rows in data centers. The racks house and protect data center equipment such as servers, routers, switches, hubs, and audio/visual components. The data center IT equipment can get very hot, so cooling is required to keep them from overheating and for proper operation. Racks in data centers are either air-cooled or liquid cooled.
Air-Cooled Racks
Cold air is brought through the front of the rack, across the IT equipment where it picks up heat, and then the hot air exits the back of the rack.
Data Center HVAC System – Air Cooled IT equipment Racks in Data Center
To increase the efficiency, blanking plates are added to direct the cold air optimally over the IT equipment positioned in the rack, and to keep the warm air from mixing with the cold entering air. It’s important to cover openings within and between racks to avoid wasting energy and directing the cold air where it is needed.
Liquid-Cooled Racks
Liquid cooling works better for racks with power densities between 5kw and 80kw, while the traditional air-cooled rack power densities are between 1kw to 5kw.
There are many different designs for liquid-cooled racks, here are four types.
Racks with integral coils
Rear Door Heat Exchanger
Liquid on-board cooling
Liquid immersion cooling
Liquid cooled IT equipment Racks in Data Center
Here is a liquid-cooled rack with integral coil or heat exchanger. The cold liquid circulates through a heat exchanger located in the rack. There are small fans that circulate air over the IT Equipment to capture the heat and bring it to the Cold Heat Exchanger, thereby absorbing the heat into the liquid and sending cold air over the IT equipment. This is one type of liquid cooled system, but there are many different versions with each manufacture trying to achieve greater efficiencies with their designs.
Liquid has the capacity to transfer heat up to 4X higher than the capacity of air of the same mass. This makes liquid cooled systems the ideal choice for the ever-increasing heat loads of rack equipment.
We looked at several rack configurations, let’s see how they are organized in the overall data center layout.
Data Center Layouts
You walk down aisles between racks lined up in rows on both sides in a typical data center. These aisles are either receiving cold air or rejecting hot air from the IT equipment. So, you’re walking down either a hot or cold aisle.
The traditional method was to use no containment of either the hot or cold air within these aisle in the data center. The thinking was to push the supply air up through the raised floor hoping the majority would make it through the rack before mixing with the hot air. With the increase in heat being generated per rack growing, this strategy of uncontained air is inefficient. There are better more efficient solutions, but first let’s explain a little about raised floors.
Raised Floors – Supply Air Plenum
Raised floors are common in larger data centers using air-cooled systems. A raised floor can be supported from 6” to 30” off the main floor to provide a supply air plenum space. The cold air delivered to the underfloor plenum will be supplied to the IT equipment through tiny holes in the floor tiles. Not all floor tiles in the space have these tiny holes in them, but only where needed to provide cold air.
Raised Floor in Data Center
The cold air will flow through these perforated tiles and enter the servers, picking up their heat, causing the heated air to rise above the servers where the return air suction of the HVAC units pulls the warmed air back into the cooling unit. All the server racks are facing the same direction to control the flow of air in one direction.
There are many options for providing the cold air or liquid that is circulated to the racks, here are a few of those.
Data Center HVAC Equipment Types
The most efficient strategy in air-cooled systems is to capture the heat before it mixes with the cold air. This avoids mixing the two air streams, the hot and cold air. There are three common methods of distributing the air to the racks, and that is either room, row or racked based.
Data Center Room Based Design
The most efficient solution is to implement an air management strategy.
Air Management
Proper air management in data centers dictates that you should keep the cold and hot air from mixing. It’s important that the cold supply air enter the heat-generating IT equipment without mixing with the hot exhaust.Heat should be returned to the cooling system without mixing with the cold air.
By separating the supply air from the return air within the space a more efficient system can be created. This containment strategy is better than the traditional non-containment methods.
This provides for delivering cold supply air in one aisle and removing warm return air in another. The server racks are arranged so that the cool air flows through them from the cold side through the warm IT equipment and into the warm aisle before returning to the top of the CRAC unit where the return air opening is located.
No containment of the hot or cold air in this data center with a raised floor supply air plenum
Cold air is pressurized in the underfloor plenum causing the supply air to flow through the perforated floor tiles aligned in the cold aisle. Cold air enters the IT equipment racks and absorbs the heat before being discharged into the hot aisle. Warm air from the hot aisle is pulled back to the CRAC or CRAH unit. This transfers the heat from the IT equipment to the DX or Chilled water coil where it will then be expelled outside.
Since the room is completely open with no physical barrier between the supply/cold aisle and the return/hot aisles there are some losses occurring due to mixing of the supply and return air. Hot air will migrate over the rack and be recirculated back into the top front of the rack, causing short-circuiting and a loss of efficiency.
Inefficiency can be resolved by establishing a cold or hot aisle containment strategy. Either of these methods will increase the efficiency of the cold supply air entering the Rack and avoid mixing. Aisle containment improves energy efficiency while allowing for uniform inlet temperatures for IT equipment and avoiding hot spots.
Temperature entering the IT equipment must be set correctly, as too low of a supply air temperature waste energy, while too high of a supply temperature leaves the rack temperature too hot.
When designing High Density data centers, its best to use the Hot Aisle Containment strategy, as insufficient cold air reaches the racks in the CAC arrangement.1
Cold Aisle Containment (CAC)
By isolating the cold air to just the front of the server racks with no opportunity to mix with the return we can increase our efficiency and delivery of the cold supply air to the front of the server racks. By putting a containment barrier on the cold aisle, we can direct the cold supply air to the front of the server where it is most useful.
Cold aisle containment strategy in a Data Center.
Cold air has nowhere to go accept through the racks where it picks up the heat from the IT equipment before entering the hot aisle where it will rise and be pulled back to the HVAC equipment. Hot air is not contained within the space.
Cold Aisle Containment in Data Center
Using the cold aisle containment method, the cold air is contained within the cold aisle, while the warm return air is allowed to circulate throughout the whole data center. The two air streams are separated by some form of containment enclosure on the supply side.
Hot Aisle Containment (HAC)
Using this strategy, the hot air being exhausted from the racks is contained to just the hot aisle and is pulled into the ductwork or a plenum and sent back to the HVAC equipment without mixing with the cold supply air. This can work with or without a raised floor, as the supply is not contained within the room.
Hot Aisle containment strategy in a Data Center
The hot aisle is enclosed keeping the hot air from the IT equipment contained, while the cold air is allowed to circulate throughout the data center, the direct opposite of the cold aisle system.
Hot Aisle Containment in a Data Center
Computer Room Units
There are several different styles and configurations of computer room HVAC equipment. Some sit on the ceiling, others sit on a raised floor, while others can sit in-row between the Racks and not require a raised floor. Traditionally the two most common HVAC systems for medium to large data centers was either a CRAC unit, that is a Computer Room Air Conditioner or a CRAH, Computer Room Air Handler. These are just a big box containing fans, cooling coils, filters, and options like humidifiers. The two units look similar, it’s’ just the way they cool the air that’s different.
It’s common to find a raised floor system in a data center, where the cold air is supplied to a plenum under the IT Equipment. The HVAC units are strategically located throughout the Data center floor area and provide cold area in a downflow pattern into the open plenum space below the floor.
The difference between the two is that the CRAC units are DX cooled and have a DX condenser outdoors to support the indoor unit. The CRAH unit is provided with chilled water and has a chiller as the source.
The traditional room based cooling systems are reaching the limits of their capabilities in some data centers. Higher density blade servers pack a lot of power in a small space, which means more heat. The room-based systems are designed for lower density racks and simply can’t keep up with the heat load, which can create hot spots.
To address this problem, cooling solutions can be brought closer to the source of the heat, which is generated in the rack. These systems are often referred to as close-coupled cooling systems, which can be used instead of, or in addition to standard room based cooling systems. This would include In-row and In-rack systems.
In-Row Cooling Units
In-row cooling units sit between the IT equipment racks and take the hot air from the hot aisle, and cool that air before blowing it into the cold aisle where it gets sucked into the IT equipment racks to cool down the equipment. Each of these In-row CRAC units is dedicated to one row of racks, and despite their name can be installed overhead or under the floor in addition to the in-row versions.
In-Row cooling units to cool a row of IT equipment racks in a Data Center
Being close to the racks saves on fan energy and increases energy savings. In-row CRAC units also allow for different cooling capacities per row to handle varying load profiles of the server racks. One row of racks may generate more heat than another because of the type of IT equipment in the rack.
A raised floor is not required for this design which saves money and increases floor load bearing capacity.
The hot aisle must be designed with a roof and doors on the sides to allow access. The roof and sides keep the hot air contained so it doesn’t mix with the cold air. With In-row units the source of cooling is closer to the heat load, minimizing the mixing of hot and cold air streams.
In-row cooling units can be served with chilled water, or they could be self-contained mini air conditioners that only need to be plugged into the 208/240V outlet. For higher density data centers using in-row units, chilled water would be the better solution.
Rack Cooling
There are various rack cooling designs, including directly mounted to the rack or housed within the rack itself. These systems are dedicated to one server rack.
One option is to have self-contained racks that have their own air conditioner, but these are limited in size. For higher densities you’ll have chilled water fed to these rack cooling systems. The rack can have a heat exchanger mounted on the back that absorbs the heat being ejected from the IT equipment. Up to 60 kw per rack can be achieved using this method.
In-rack Cooling of IT equipment in a Data Center
For more information see the link to the government’s energy star article for in-rack cooling.
There are some data centers that use a combination of the three systems because of the varying densities of load.
Racked based systems are more costly to purchase especially as the power density decreases. But the energy savings for a rack based system will be less annually in electricity cost.
CDU – Cooling Distribution Units
Cooling distribution units provide separation between the IT equipment in the racks and the outdoor heat rejection equipment like a cooling tower or dry cooler. The heat exchanger in the CDU keeps the two water systems separated so they never mix, allowing the liquid circulating in the racks to be unaffected by the water circulated outdoors. Water from the tower is circulated to the primary side of the heat exchanger in the CDU where it absorbs the heat from the secondary water circulating through the racks.
Inside the CDU are redundant pumps that circulate secondary water to various racks.
The CDU provides water to the IT rack equipment that is above the dew point temperature to avoid condensation issues.
Cooling distribution unit distributes cold liquid to IT equipment racks in Data Center
CDU’s can be very energy efficient because it avoids the use of refrigeration equipment like chillers and DX coils using compressors. The CDU will use a Dry Cooler or Cooling Tower for heat rejection. With some manufactures you can achieve 5kw (17,060 Btu/hr.) to 30kw (102,360 Btu/hr.) per rack of heat removal.
These systems are usually cost effective compared to most other systems. In case of a leak, they have very small volumes of water in their secondary loops compared to a chilled water system used with other rack cooling strategies.
With the amount of time spent indoors, it makes sense to find ways to increase the quality of your indoor air for yourself or your customers. Indoor air quality is often worse than the outdoor air unless you live near a factory or refinery.
We are in the business of providing quality indoor environments so we thought we would share some of the best ideas to help you make yours or your customers home safer and the quality of the air better. These top 12 are not our opinions, but facts derived from research which we’ll include links to if you want to research further.
We’re not being alarmist, but wise stewards of responsible clean living, especially if you have young children in the home, as we’ll show you ways that they are being poisoned that you may not have heard about. See the link to our website where you can download a PDF for yourself or a customer.
To watch our FREE YouTube Video of this presentation, please scroll to the bottom.
Reduce Toxins in Your Life by Following these top 12 Ways to Increase Indoor Air Quality
#1 Properly Vent Fireplaces and Stoves
Ensure that all combustion appliances such as fireplaces and wood stoves are vented properly. According to the EPA Smoke forms when wood or other organic matter burns. The smoke from wood burning is made up of a complex mixture of gases and fine particles. In addition to particle pollution, wood smoke contains several toxic air pollutants including benzene, formaldehyde, acrolein and polycyclic aromatic hydrocarbons.
Properly Vent all Combustion Processes. Avoid inhaling smoke and Particle Matter PM
You may like the smell of burning wood, but it’s definitely not good for you, especially the fine particles that are emitted. These microscopic particles can cause havoc to your eyes and your respiratory system, with the possibility of burning eyes, runny nose, and illnesses like bronchitis, the triggering of asthma, heart attacks, stroke, irregular heart rhythms and heart failure. This isn’t our opinion these are the words of the EPA, which you can check out in the link below.
Avoid or minimize the use of any unvented combustion by-products such as the burning of candles, tobacco products, un-vented heaters, indoor barbecues. The majority of candles are made of paraffin wax, which is made from petroleum waste, and when burning give off highly toxic benzene and toluene, both are known carcinogens, basically they cause cancer. If the candle is scented then there are additional concerns from the harmful effects of the chemicals in the fragrance.
Avoid Candles made from Paraffin Wax (aka Petroleum)
Use alternative candles such as those made from beeswax, coconut or 100% soy. Use candles scented with essential oils instead of toxic chemicals. Checkout the website in this link for more information. MadeSafe.org
#3 Plants per NASA and Biophilia
Fill your home with plants that provide air scrubbing abilities or by adopting the calming effects from biophilia. Biophilia is defined as the innate human instinct to connect with nature and other living things. This is done by bringing the outdoors, indoors.
Biophilia – Bring the Outdoors, Indoors & Indoor Plants for better Indoor Air Quality
According to NASA there are certain indoor plants that can absorb toxins from the indoor air. They list the top 12 indoor plants for increased indoor air quality. See the link to NASA report in the description below.
See more information on Biophilia in the link below, and how you can increase indoor well-being by bringing the outdoors, indoors.
Dust can contain harmful Toxins especially for small children
#4 Clean on a Regular Schedule
Clean on a regular schedule using a quality vacuum cleaner, microfiber cloths and non-toxic alternative cleaners and methods. Toxins stick to house dust and soil that is brought into the house. These toxins can be inhaled when dust is kicked up, while some could also be unknowingly absorbed through the skin or swallowed by hand-to-mouth contact. If you have small children, remember they spend a lot of time on the floors where some of these toxins can gather.
Make sure that all the rooms where smells are generated are properly vented to the outside. This would include bathrooms, laundry rooms, kitchens. The quality of the air is improved when smells are exhausted outdoors. If you have a fan powered kitchen or range hood be sure to put the fan on high speed when cooking to force any products of combustion or smells out of the home.
Open Windows for Fresh Air when the weather allows
#6 Toxins, Smells Generated Indoors – Open Windows
When cleaning or using products with strong odors be sure to open as many windows as possible to move the vapors and smell outdoors. This would include odors from nail polish as research has shown that women who work in poorly vented nail salons have higher rates of birth defects among their newborns. Even if you’re not a salon worker its best to do your nails in the backyard or a well vented area. See research paper below.
Avoid breathing in Toxins from Nail Polish and other hazardous chemicals
Also if using a spray bottle to spray your cleaner, realize that some of that cleaner will be aerated into the breathable air. Spray close to the surface or spray into your cleaning cloth. It’s even better to use a cleaner that is safe for you and the environment. Use green products, and visit the EPA website which provides plenty of healthier alternatives, see the link below.
Never store toxic, volatile, or hazardous compounds within the home. This might include pesticides, herbicides, paints, glue, cleaners, and similar items. These items could leak into the air stream at levels unnoticeable to you. And when using make sure to read the label and ventilate the space, and avoid having children around if possible. See the link in the description below for the report on Pesticides and Asthma. It’s always best to use safer, green alternatives. Checkout the Safer Choice website below for safer alternatives.
The industry standard for indoor air quality is from ASHRAE, the American Society of Heating, Refrigerating and Air-Conditioning Engineers. ASHRAE standard 62.2, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings provides guidance on this topic.
Make sure to provide the ASHRAE minimum ventilation per standard 62.2. This can be done using a whole house fan. The ventilation rate is based on the size of the home and the number of bedrooms. If you have a 3 bedroom, 2,000 Ft2 (185 m2) home then you need 90 CFM or 43 L/s of ventilation air.
Whole House Fan – Indoor Ventilation
Of course this can only be done with the proper weather conditions existing outdoors, and is usually a summer application. In summer, opening the windows during early morning or evening hours when the air is cooler can bring the temperature down and freshen the air inside. See ASHRAE standard 62.2 for more information.
Don’t locate heating and air conditioning equipment in the garage or an area where the system or ductwork could inadvertently suck in toxins from car exhaust or toxic substances stored in the garage. Also be sure to have your furnace inspected to ensure there aren’t any leaks which is a silent killer. Gas and oil burning furnaces produce carbon monoxide (CO). Carbon monoxide is an invisible, odorless, poison gas that kills hundreds every year and makes thousands more sick. Install battery backed up carbon monoxide detectors in every bedroom. See link below in the video description to the CDC’s website for more information.
Use a good quality filter or high-efficiency portable air cleaner in your HVAC system, one that filters out the dust and particles circulating in the air. The use of a MERV 13 filter or higher is best if your system can accommodate them. If you choose a portable air cleaner make sure that it doesn’t emit ozone. Make sure to replace your filters after frequent use and according to the manufactures recommendation.
Avoid purchasing products for your home sprayed with flame retardants that are considered toxic. These flame retardants can be in furniture, carpet padding, baby products and pajamas. These flame retardants can become airborne, settle on dust and items in your home. Small children often have higher levels of flame retardants in their bodies because they put their hands and household items in their mouths, causing them to swallow these toxins.
Avoid using plug-in air fresheners and other air fresheners unless you know their ingredients, as a lot of the products on the shelves today could be carrying toxic chemicals. The manufactures often refuse to disclose the ingredients claiming they are a trade secret. What’s not a secret is that these air fresheners can be toxic, including negative health effects like cancer, endocrine disruptions and neurotoxicity.
3 Phase Electricity – How it Works. We’ll be demonstrating how 3 phase electricity works by first explaining how its generated, and how it differs from single phase electricity. We’ll also cover where 3 phase power is used in industrial and commercial buildings.
To watch the FREE YouTube version of this presentation, scroll to the bottom.
How is 3 Phase Electricity Generated?
If starting at the source of 3 phase power generation, we would begin at the power generation plant, whether that was nuclear, fossil fuel or another source. AC Generators convert mechanical energy into electrical energy, while the AC motor does the opposite, it converts the electrical energy into mechanical energy like turning the motor shaft of a pump or fan.
3 Phase AC Generator Converts Mechanical Energy into Electrical Energy
The AC generator could be a steam powered turbine fed by a boiler burning coal, gas, oil or another source, such as nuclear power or a hydroelectric dam. The steam or potential energy turns the generator that produces the 3 phases we’ll be discussing now. We’ll show you a coal burning plant convert coal into electricity later.
Michael Faraday – Electromagnetic Induction and Electromagnetism
First we must pay tribute to Michael Faraday, an English Scientist who contributed to the study of electromagnetism and the principles underlying electromagnetic induction. AC Generators and Motors use electromagnetic induction as we’ll now explain.
Electromagnetic Induction
A magnetic field can be created in a conductor by passing electricity through it, or an electrical current can be induced in a conductor by passing a magnetic field past the conductor. We can accomplish this with three items, a conductor, electromagnets and movement between them.
There are many version of the AC Generator, one such version uses a rotating electromagnet to create a magnet field that conductors pass through, thereby creating electromotive force and inducing current to flow in the conductors. Another version would have the conductors moving and the electromagnets are stationary. The commonality is a electromagnet which creates a magnetic field and a conductor that is brought within this magnetic field.
3 Phase Magnetic Induction
When the north pole of the Electromagnet passes the electrical conductor windings it induces current to flow in the wire.
When the magnet is 90 degrees past the conductor windings than no current flows in the wire.
3 Phase Electricity Magnetic Induction – No current Flow
As the South pole of the electromagnet passes the conductor windings it causes the current to travel in the opposite direction as that caused by the North pole of the magnet. This causes the current to be alternating in direction as represented by the wave form.
3 Phase Electricity generated by Electromagnetism
There are three coils in 3 phase electricity, with an angle of 120 degrees between them.
3 Phase Electricity – Frequency in Hertz
What is 3 Phase Electricity
Using what we learned previously we can now assemble a basic 3 phase generator by adding three sets of windings, one for each phase. The previous single winding can be considered a single phase generator. Will need to put these windings in a housing to hold everything together.
Here is what a simple single phase generator might look like.
Single Phase Electricity
Now as the electromagnet rotates within the stator, its magnetic field cuts through the conductors inducing current to flow in an alternating back and forth pattern. Using only one conductor we get a single phase system.
Adding two more conductors we now get three phase electricity. The magnetic field of the electromagnet now penetrates the three conductors inducing current to flow in all three conductors. We get three separate phases that are 120 degrees apart giving us the most effective arrangement for power use.
3 Phase Electricity using an Electromagnet
As the magnetic field of the North pole of the magnet reaches the nearest point of one of the conductors it will force electrons and current to flow in one direction. Then when the South Pole of the electromagnetic reaches that same conductor it will causes the electrons or current to flow backwards. This back and forth push and pull of the electrons or current in the three separate windings is how three phase power is created.
While one conductor or winding is peaking in strength facing the North pole of the magnet, the others are 120 and 240 degrees away, awaiting their turn at the effects of the North pole of the magnet. This occurs 60 times in a second giving us 60 hertz, or if you’re in a country that uses 50 hertz, this will occur 50 times a second.
A complete rotation of all three phases equals one cycle, and in a 60 hertz system, that would mean 60 cycles or rotations of the rotor within the stator housing every second, for a 50 hertz system, 50 cycles per second. The cycles per second is called frequency, and is either 50 or 60 hertz. Remember motors with VFD’s can very their hertz, and if you aren’t familiar with this concept then see our video on VFD’s, Variable Frequency Drives.
Coal Burning Electricity Plant
The 3 phase electricity is generated here using dirty coal. Coal is sent to the boiler where it is burned to create steam that turns a turbine in the generator that produces the electricity. The electricity is transmitted over high voltage lines to location that will consume the electricity. The high voltage electricity will be converted to lower voltage by running it through a transformer.
Coal Powered Electricity Generation
These transformers can be located on an industrial or commercial property where the voltage will be reduced to something that is at a proper level for the equipment it will power.
Depending on the configuration of the transformer, it can be setup as a delta or Wye type transformer providing all the various voltages required in the building. From this 3 phase electricity everything in the building can be powered whether requiring single or 3 phase. The lights in your home will use 115 volts or something similar while a commercial building may use 277 volts, single phase for their light fixtures, as 277V is more efficiently distributed.
Your home will only require single phase electricity while commercial and industrial buildings can use the more efficient and powerful 3 phase power for their equipment, such as Pumps, Fans, Chillers, Elevators, hospital equipment, etc. The 3 phase power allows the industrial and commercial buildings to also use just a single hot wire to get single phase to run office equipment like computers, vending machines, calculators and other low voltage items.
