Parts of a Deer Antler - Deer Rack Anatomy 101

Deer antlers are an incredibly fascinating biological phenomenon. The shape of antlers range from very small sharp "spikes" to fantastical typical and non-typical racks. To better understand the parts of a deer antler, we will first examine some basic deer antler terminology, the difference between horns and antler then follow up with the correct name for every part of the deer antler.

Antler Terms

Point: a projection on an antler that is at least one inch long.

Parts of a Deer Antler - Deer Rack Anatomy 101

Rack: refers to the set of antlers on a particular deer. All racks are divided into two classifications; typical or non-typical.

Typical: typical racks are those antlers that look like a a classic or "normal" rack. On a 10 point buck (a buck with a rack that has a total of ten points,) the buck would show five matched points on each side, and the location of these points would be in typical locations.

Non-typical: non-typical racks, by definition, are racks that do not look normal. They may exhibit unmatched points (for example 3 points on one side and 5 on the other,) they can have points growing off of other points or the points themselves may be abnormaly shaped.

Antlers vs. Horns

Horns are found on mountain goats, bighorn sheep, bison and other game. Horns, unlike antlers, grow all throughout an animals life. If they are lost or damaged for any reason, they cannot be replaced. The surface of horns is made of a keratin, much like human finger nails. They are alive, in that they receive nutrients by blood vessels that are inside the horn.

Deer, like elk and moose, have antlers, not horns. Antlers, are not made of keratin, they are dead bone that grow out of the skull of the animal. Antlers tend to be much longer than horns, and have numerous branches. Deer grow yearly and shed their antlers on a yearly basis. Antler tissue is said to be fastest growing mammal tissue known to man. Even the largest rack on a mature deer is grown in about three to four months!

Parts of a Deer Antler

Pedicle: The base of the deer's antler, where the antler bone meets the head of the deer.

Beam: The central stem of the antlers, from which all other points arise.

Brow Tine: The first division or point off of the beam.

Bay Antler: The second division (or point above the brow tine).

Royal Antler: The third division on the antlers (or point above the bay antler).

Surroyal Antler: The fourth division or point above the royal antler.

Fork: The end of deer's antlers, where the central beam divides in two.

Palm: The end of a deer's antlers where the central beam divides into several points, resembling the human hand.

Crown Tine: A tine growing at the very end of the deer's antler, the points above the fork or palm.

These terms should help you correctly identify and discuss the different parts of a deer antler.

Parts of a Deer Antler - Deer Rack Anatomy 101
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You can see a picture of a deer rack that points out the different parts and learn more about deer hunting at deer hunting tips.

Nick Moran is an avid sportsman and author writing about hunting and fishing issues in the United States.

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Grounding Transformers - Electrical Design, Transformer Design, and Distribution Transformer Design

Grounding is clearly one of the most important aspects of electrical design, but it steadfastly continues to be misinterpreted and misunderstood. Millions of dollars in liability and loss can be attributed to ground-fault arcing; thus, grounding-related issues should top the checklists of any electrical contractor.

Grounding Transformers:

Simply put, a grounding transformer is used to provide a ground path to either an ungrounded "Y" or a delta connected system. Grounding transformers are typically used to:

Grounding Transformers - Electrical Design, Transformer Design, and Distribution Transformer Design

Provide a relatively low impedance path to ground, thereby maintaining the system neutral at or near ground potential Limit the magnitude of transient over voltages when re-striking ground faults occur Provide a source of ground fault current during line-to-ground faults Permit the connection of phase to neutral loads when desired

If a single line-to-ground fault occurs on an ungrounded or isolated system, no return path exists for the fault current, thus no current flows. The system will continue to operate but the other two un-faulted lines will rise in voltage by the square root of 3, resulting in overstressing of the transformer insulation and other associated components on the system by 173%. MOV lightning arresters are particularly susceptible to damage from heating by leakage across the blocks even if the voltage increase is not sufficient to flash over. A grounding transformer provides a ground path to prevent this.

Large multi-turbine wind farms provide an example of the use of grounding transformers for fault protection on ungrounded lines. In many wind farms the substation transformer provides the sole ground source for the distribution system. When a ground fault on a collector cable causes the substation circuit breaker for that cable to open, the wind turbine string becomes isolated from the ground source.

The turbines do not always detect this fault or the fact that the string is isolated and ungrounded; thus the generators continue to energize the collector cable, and the voltages between the un-faulted cables and the ground rise far above the normal voltage magnitude as described above. A grounding transformer placed on the turbine string provides a ground path in the event the string becomes isolated from the system ground.

Construction:

Grounding transformers are normally constructed either with

A ZigZag (Zn) connected winding with or without an auxiliary winding or As a Wye (Ynd) connected winding with a delta connected secondary that may or may not be used to supply auxiliary power

The geometry of the Zig-Zag connection is useful to limit circulation of third harmonics and can be used without a Delta connected winding or the 4- or 5-leg core design normally used for this purpose in distribution and power transformers. Eliminating the need for a secondary winding can make this option both less expensive and smaller than a comparable two-winding grounding transformer. Furthermore, use of a Zig-Zag transformer provides grounding with a smaller unit than a two-winding Wye-Delta transformer providing the same zero sequence impedance.

Wye connected grounding transformers, on the other hand, require either a delta connected secondary or the application of 4 or 5 leg core construction to provide a return flux path for unbalanced loading associated with this primary connection. Since it is often desirable to provide auxiliary power from the grounding transformer secondary winding, this benefit can sway the end user to specify a two-winding grounding transformer in lieu of a Zig-Zag connection. The current trend in wind farm designs is toward the Wye connected primary with a delta secondary.

It is important to understand that both Zig-Zag and two-winding grounding transformers can be provided with the ability to provide auxiliary power, and this can be either a Wye or Delta connected load.

A solidly grounded system using a grounding transformer offers many safety improvements over an ungrounded system. However, the ground transformer alone lacks the current limiting ability of a resistive grounding system. For this reason, neutral ground resistors are often used in conjunction with the grounding transformer to limit neutral ground fault current magnitude. Their ohm values should be specified to allow high enough ground fault current flow to permit reliable operation of the protective relaying equipment, but low enough to limit thermal damage.

How to Specify a Grounding Transformer

The basic parameters required for quoting a grounding transformer are:

Primary Voltage - This is the system voltage to which the grounded winding is to be connected. Don't forget to specify the BIL also. In some cases the BIL will be dictated by equipment considerations, such as 150 kV BIL ratings on 34500 volt wind farms because of the limitation on dead front connectors. Rated KVA - Because the grounding transformer is normally a short time device, its size and cost are less when compared with a continuous duty transformer of equal kVA rating. For this reason, grounding transformers are often not sized by "kVA" but by their continuous and short time current ratings. Regardless of how you rate it, the grounding transformer must be sized to carry the rated continuous primary phase current without exceeding its temperature limit. This load includes the magnetizing current of the core, the capacitive charging current for the cables, and any auxiliary load if applicable. The higher this value, the larger and more costly the transformer will be. Typical continuous current values can be as low as 5 amps to as high as a few hundred. Be sure to include any auxiliary loading requirements. Continuous Neutral Current - The continuous neutral current is defined as three times the phase to current, or in other words, the zero sequence current. This is usually considered to be zero if the system is balanced. However, for the purposes of designing a grounding transformer, it is a value that is expected to flow in the neutral circuit without tripping protective circuits (which would force the current to be zero) or the leakage current to ground that is not a symmetrical function. Again this value is needed to design for thermal capacity of the grounding transformer. Fault current and duration - This value is needed to calculate the short time heating that results from a fault on the system and should be determined from an engineered system study. Typical values for this range from a few hundred amps to a few thousand amps with duration times expressed in seconds and not cycles. For instance, a value of 400 amps for 10 seconds is typical. The fault duration is a critical parameter for the transformer designer. Where protection schemes use the grounding transformer for tripping functions, a relatively short time duration is specified (5 -10 seconds). On the other hand, a continuous or extended neutral fault current duration would be required when the grounding transformer is used in a ground fault alarm scheme. Impedance - The impedance can be expressed as a percentage or as an ohm value per phase. In either case it should be chosen so that the un-faulted phase voltages during a ground fault are within the temporary over-voltage capability of the transformer and associated equipment, such as arresters and terminal connectors. Because of this description, the values can vary from as low as 8% to almost 100%. This value must come from the system designer. Primary winding connection - Specify the type of primary connection, either Zig-Zag or grounded Wye. Secondary connection - specify the secondary voltage and connection when applicable. Specify the size of auxiliary loading to be connected for either Zn or Wye connected primary windings. If the option is to have a two winding transformer with no secondary load, advise if the delta winding can be "buried" (that is not brought out) or if only one bushing is to be brought out for grounding to the tank or testing.

· Basic overall construction features - note the following features as they apply to each transformer
· Compartmental Padmount transformer with integral tamperproof compartment or substation design
· Outdoor or indoor
· Fluid type- mineral oil, silicone, Envirotemp FR3
· Connectivity -dead front, live front, spade terminals, location of terminals - cover or sidewall , exposed or enclosed, etc
· Temperature rise is assumed to be 65'C
· Site elevation or environmental concerns
· Special paint as required
· Neutral Ground Resistors - The rated voltage of the NGR should be equal to the line to ground voltage of the grounding transformer. The current rating and duration should match the grounding transformer ratings. Remember to set the current rating high enough to be above the cable charging current and grounding transformer magnetizing current.

Grounding Transformers - Electrical Design, Transformer Design, and Distribution Transformer Design
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Mike Dickinson began his carrier in transformer industry in 1972 at Pacific Crest Transformers. Currently Mike is in charge of Business Development at PCT. Pacific Crest Transformers is a leader in the design and construction of distribution transformer.

Read more about transformers, grounding transformers and related information at PCT.

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How Much Overhang Can My Granite Countertop Have Without Additional Support?

How much overhang can I have without additional support? The short answer everyone is looking for is 12 inches. The Marble institute of America recommends no more than 12 inches unsupported. This short answer is not enough as there are variables that must be understood to safely answer this question. The maximum overhang depends upon the hardness of the stone and just how much counter IS FULLY supported vs how much is not. Cantilevered weight offset, is what we are looking for.

Here is an extreme example. If you only have 6 inches of stone on top of a wall cap then the maximum safe overhang is 2 inches following the 2/3rds rule. The Marble institutes 12 inch guide line may lead someone to believe that it is OK to have 12 inches of overhang when in this situation it would immediately fall off the wall and potentially injure anyone with feet in the path of the falling granite.

So to clarify the maximum overhang is the lesser of 2/3rd or 12 inches. Even that depends upon the fragility of the material. I would not recommend a 12 inch unsupported overhang with Onyx due to how soft and fragile the material is and you can get away with 16 inches if the material was Absolute Black as the material is fissure free and extremely hard.

How Much Overhang Can My Granite Countertop Have Without Additional Support?

How much overhang can you have without additional support? This question comes up daily and affects layout and overall design of many kitchens.

The straight answer is up to 12 inches for granite, providing 2/3 or more is cantilevered to offset the unsupported weight.

Peninsula overhangs can make or break the overall functionality of a kitchen. The use of Corbels or legs to support additional overhangs can affect chairs and leg areas so finding solutions can affect the functionality of a kitchen design.

You can have more and sometimes less is recommended depending upon the actual stone. Very hard stones can safely support more overhang, providing the 2/3 cantilevered criteria is met. Softer or more fragile stones may dictate less overhang.

What options do you have if you just have to have more overhang. well there are couple different ones to consider.

Below are some of the popular solutions and options as well some pros and cons to each solution.

-Corbels- Visible but decorative

-Brackets- Inexpensive and effective, installed properly works better on wall tops than upon cabinets
themselves.

-Legs -Visible, decorative but in the way of chairs and peoples legs.

-Granite Countertop support brackets- Hidden and concealed but offers great support. They must be installed before the granite and cut into the cabinet itself. They are specifically designed for this challenge.

-Rods- Can be installed inside of the stone to strengthen and potentially extend the limit as this technique does reinforces fragile stones, but does nothing to extend the cantilever rule of 2/3rds.

Think a worst case scenario such as someone deciding to jump up on top of a countertop and ask yourself, "would that be safe" Consider the application as well. what is safe in a frat house is not the same for what is safe in a retirement community. Consider the application, material, cantilever support and err to the safe side when designing and planning the amount of overhang you might engineer into your granite countertops.

Dan DiTomaso Stone Masters Inc. http://www.stonemastersinc.net

How Much Overhang Can My Granite Countertop Have Without Additional Support?
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Dan DiTomaso
Stone Masters Inc
http://stonemastersinc.net/

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Bandsaw - How to Resaw

A Bandsaw give you freedom to design and build anything you want. If you want 5/8" drawer sides, you should have them. Resawing on the Bandsaw gives you the ability to cut stock thickness quickly, safely, and efficiently.

Resawing allows you to control the thickness of wood. After resawing and one or two passes through a thickness planer, you are free from the yoke of standard thickness. Are you content with only 3/4" wood for everything you build?

Resawing is nothing more than taking a piece of wood and cutting it into thinner pieces. The bandsaw is the ideal tool for this job. It is far safer than a tablesaw.

Bandsaw - How to Resaw

Its narrow kerf and vertical blade movement make it extremely efficient. It wastes minimal wood. Cutting is easy and quick. All you do - cut straight lines. A board with one square edge and side is necessary.

Problem is, most woodworkers don't have a clue how to do this. Successful resawing calls for nothing more complicated than appropriate blade selection, adequate tension, setting the fence, and proper stock control.

Blade Selection: As you saw through very thick stock, you put a lot of pressure on every part of the blade engaged in the cut. Each saw tooth shaves out waste. Blades with 3 teeth per inch (tpi) have large gullets which have room for a lot of waste.

Thrust bearings support the blade above and below. During the actual cut, only the blade's stiffness or "beam strength" will keep the cut proceeding straight and free of wander. It's my experience that a quality 1/2" 3-tooth blade gives good results. I tried wider blades with no increase in efficiency.

Tension: Adequate blade tension reduces the blade's tendency to lead erratically under thrust. I have found that the standard tension gauge is not accurate. It is better to use a little more tension than indicated.

You can check it by opening up the thrust bearings and lateral guides. Back off both above and below the table so they do not contact the blade. Crank the tension gauge to the desired setting. Give the blade a sideways nudge about halfway between the upper and lower wheels. The blade will deflect easily for a short distance. This sideways movement should be 1/4". If you push harder, it will bend farther but there is a distinct point where it quits deflecting easily. If you can deflect more than 1/4", then add tension until this deflection is 1/4".

Stock Control: How does one cut straight lines? Answer: find out how the saw wants to do it, and do it that way.

Every good bandsaw blade can cut straight lines. Each blade will do so in its own way. In other words, each blade has its own "lead angle". How can we determine this lead angle?

Some experts suggest using a Resaw Guide. This is like a single point, which allows you to change the angle of your feed into the blade. It takes practice to use this method. Moreover, this technique requires constant attention.

If you have to figure out the right feed direction, why not just do it once? Then set your bandsaw fence accordingly, and cut straight lines. It is just that easy.

Ensure that the blade and fence are both 90-degrees to your table. Take a straight piece of wood about two to three feet long. Mark a line down the center. Cut freehand along the line, trying to keep the cut on the centerline. Feed at a normal pace. Once you have it straight, hold your piece of wood to the table. Turn off the bandsaw. You have found the lead angle for this blade!

With a pencil, mark a line on the bandsaw table along the piece of wood. Loosen the fence's bolts with a wrench. Set the angle of the fence along the pencil line of the test cut. Tighten your bolts. Your fence is now set for the blade's correct lead angle. This gives you straight cuts. Set once and cut. What could be simpler?

You may want to practice your feed speed. It is a good idea to mark a line on your intended cut for the first several boards. It just gives you faith that the cut is straight.

You will gain confidence with this method. It gives you more versatility with your projects. With a little practice, you can't go wrong. Have fun while resawing with safety in mind!

Bandsaw - How to Resaw
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Jim is a woodworker with over 36 years of experience. He helps many woodworkers increase their skills with techniques, tips, plans, and jigs. Helping woodworkers is Jim's expertise. Visit his specialty site at provenwoodworking.com

For more information, including pictures and tips, please visit Woodworking Bandsaw

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Considerations For Owning a Self-Service Carwash Business

Owning and operating self serve and self serve automatic carwashes, can be profitable and enjoyable as well as a good investment. However, there are several factors that need to be considered to maximize your return as well as operate your wash efficiently. The following are major considerations when you are planning to invest in the car wash business.

What Location should I chose?

Design Considerations

Like real-estate and retail, location is critical for maximizing profits. Having a carwash out in the middle of nowhere obviously will result in low traffic. You want to be located in high traffic residential areas near retail centers. The ideal location is a corner lot where the carwash is easily accessible from east-west traffic and north-south traffic. The streets should have 30-35 mile per hour speed limits. Often times, a location can be cut off from traffic on the opposite side of the street. A potential customer who has to drive a block past your place and make a u-turn to get to your carwash may opt to find a different wash.

Considerations For Owning a Self-Service Carwash Business

You also need to investigate all known future changes in the location. Are there any changes to traffic flows, is a major retail store leaving (or coming), and are there any potential changes in local zoning laws or ordinances. Are there any potential road construction projects that could affect traffic?

The property should be large enough to accommodate the size wash you want to build as well as have enough room for several vehicles to wait in line safely. City or local ordinances may apply as well. Avoid industrial areas.

What Carwash Equipment should I Buy?

Choosing a low maintenance high reliable carwash system is extremely important for generating revenue and keeping your costs down. A carwash that breaks down frequently will lose customers and drive your operating cost through the roof. A carwash that does not effectively clean the vehicle will lose traffic. There are many types and styles of carwash systems, but the two most important considerations are 1- good cleaning ability, 2. Reliability. One should do a fair amount of research when selecting the equipment, getting references and field data will be helpful in making your best choice.

Make sure that there is a local dealer or distributor that is qualified to service your equipment. Having someone available for fast service or repair is a must for maintaining a continuously open carwash.

How Much Time to Invest?

One needs to be prepared to do daily maintenance, cleaning and inspection regardless of type and make of equipment. Keeping your carwash clean and attractive looking will keep customers coming back to your car wash. Conversely, dirty, run down carwash will turn away a lot of potential clients. One needs to maintain the coin machines regularly, and keep chemicals and other items in supply. It is not unreasonable to expect to spend 2-3 hours every day at a 4 stall carwash; you should assume some part time help on the weekends as well. There is also scheduled maintenenance that needs to be done. Changing oil in pumps and replacing filters are a couple of examples of maintenance activity that needs be done a few times per year. Maintenance intervals will depend on equipment and amount of traffic, your carwash manufacturer will supply you with the recommended maintenance intervals.

One should not expect to do equipment overhauls or part replacements in the first year of operation, but any one in it for the long haul should be prepared for equipment updates and overhauls periodically. Having a local distributor/ dealer will be very important for keeping your carwash operational.

Having a good preventative maintenance system will go along way to ensuring maximum profitability and customer satisfaction.

How should my carwash be configured?

The more options your carwash has and the larger variety of vehicles that you can handle, the more traffic you will get. One should probably have 2-3 self service "manual" stalls with a stall equipped with an automatic system. Many customers prefer the do-it- yourself system.

Your automated system should also offer several options, allowing a lower cost "quicker clean" and a higher end clean with wax options will attract the most customers. Make sure you don't compete with your do it yourself stalls on the low end, nor with the "high end" full service carwash down the road.

Most new carwash systems can handle the larger SUV and trucks, but one should make sure that your automated carwash system can handle a variety of vehicles.

What kind of Traffic Can I Assume?

Traffic will vary greatly depending on location, season of the year, day of the week and even time of the day. In the Upper Midwest, November through February gets much heavier traffic than the other months because the cars get dirtier faster in the winter. One should expect 20% to 30% more traffic during these peak months than the off months.

The weekend (Friday, Saturday and Sunday) are the busiest days of the week and you may require additional help to manage your carwash during this time. Car wash traffic will drop off when the sun goes down, so you can expect higher levels of traffic in the 9:00 am to early evening times.

One estimate of number of vehicles washed during a day would be 20 to 40 cars on a week day and 50 to 70 cars on a week end day. This of course can vary greatly based on location, car wash configuration and seasons of the year and of course weather.

How Much Can I Charge?

Rates do vary depending on area of the country and local competition. For example some car washes on the West Coast have a greater start up cost than car washes in the Midwest. To make sure that you are competitive be sure to check out your local competition to justify your start up time.

Adding vending machines can also increase revenue. Wiping towels, car cleaning supplies and fragrances are some options for your vending machine.

What are My Operational Costs?

Taxes, property and facility costs, interest on loans, supplies such as chemicals, equipment maintenance and upgrade costs along with part time help for weekends and peak times need to be investigated before starting a carwash business. You should be prepared to pay an attendant 8-16 hours per week for weekend coverage.

Considerations For Owning a Self-Service Carwash Business

Douglas McLain has been in the carwash equipment business since 1972, and has been president of A-OK Equipment & Supply Company since 1979. A-OK Equipment design and builds car wash equipment including self service car wash equipment and automatic car wash equipment.

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How To Create A Solar System Science Fair Project

Science fair projects are very helpful to motivate the students towards scientific study. It also provides the possibility of observing the real world and related problems in a closer way. It aims to develop curiosity about science and technology. It brings about improvement in the manipulative skills, knowledge, and self-confidence.

Solar system began forming 10 to 12 billion years ago as a swirling gas and dust formed a dense core. To visualize the Solar system, understand the orbital motion of the planets and to locate the actual position of the planets the solar system science fair projects are helpful.

Some simple solar system science fair projects ideas include answering questions such as:

How To Create A Solar System Science Fair Project

- Can we collect micrometeorites from the outdoor sources?

- Could the other planets support any life?

- What causes the phases of moon and what affects the phases of moon?

- How terrestrial planets are formed?

- Are there many other solar systems in the universe? Do they support life?

To study about the other galaxies and solar system present in this universe this project will be useful. A comparative study of why life is possible on earth and why not life is possible on other planets can be done in detail. Younger children can also build a model of the solar system and show the relationships between the planets.

Also consider looking at natural forces which occur in the solar system, such as exploring a question like, how are the magnetic fields affected by solar storms? Can we build a homemade magnetometer to measure that? The magnetic fields are affected by solar storms and cause small changes in its direction at the surface, which are called "magnetic storms." A magnetometer operates like a sensitive compass and senses these slight changes in the magnetic field. A homemade magnetometer can be constructed.

Can we identify black holes? If the answer is yes, how can it be done? By this project, the mysteries and curiosity about the black holes will take a shape and a clear knowledge about black holes can be gained. A thorough understanding of the nature of black holes is neceessary, and a lot of background information will be necessary for such a project.

You can make your own comet to know the details about the comets. A large comet is a spectacular sight and is a star like celestial body, which has a tail and still people have lots of doubts about it. To know better, this project will help out.

How to locate the position of a celestial body by a sidereal pointer? A sidereal pointer is an instrument that helps you to locate each celestial body in the night sky. How to construct a sidereal pointer easily can be discussed in this project in detail.

Solar system science projects are fairly demanding projects that represent a challenge. Each of the projects related with solar system science projects develops cognitive skills and help the students to leap forward.

How To Create A Solar System Science Fair Project

Jordan Matthews is a High School Math and Science teacher who has worked as a judge and a coordinator of many science fairs. Check his Science Fair Project ideas website for some more ideas and information about constructing some solar system science fair projects.

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Power Transformers Testing

Testing of transformer is done to determine their electrical, thermal and mechanical suitability for the system where they will be applied or used. Most of the tests performed on power transformers are defined in national standards created by IEEE, NEMA and ANSI, whose purpose is to define a uniform set of tests recognized by both the manufacturer and the user.

Transformer Test Details:

Design Considerations

Field Testing. Field testing can be divided into three categories 

Power Transformers Testing

Acceptance tests Periodic tests Tests after failure Acceptance tests should be performed immediately after the product arrives at the destination. A few tests can be carried out which are stated below:

Turns ratio Insulation resistance(Winding and core) Power factor Resistance (winding) Polarity and phase relation Oil tests (DGA, moisture, dielectrics, etc.) Visual inspection Periodic tests are done after the product is installed in its permanent location. The main purpose of this test is to monitor the condition of the unit so that any potential trouble may be spotted early before a failure occurs. Some of these are listed below:

Turns ratio Insulation resistance  Power factor Resistance (winding) Oil tests (DGA, moisture, dielectrics, etc.) Excitation current test Visual inspection An unscheduled outage and the potential of outright failure can be prevented by following a periodic test schedule.

Failure tests conducted on electric transformers are:

Turns ratio Insulation  resistance  Power factor Resistance Oil tests Excitation current test Combustible gas/ gas-in-oil analysis Visual inspection (internal) When a transformer fails, the time of failure tests will decide whether the unit can be repaired at the site or whether it needs to be returned to the manufacturer, or a specialized center for repair. By comparing the results of the tests with the established norms, a 'history' of the transformer can be compiled, and the reasons for failure can be diagnosed.Here is a quick overview of the above mentioned tests:

Transformer Turns Ratio Test (Common to all categories)The Transformer Turns Ratio test (TTR) is used to make sure that the Turns Ratio between the windings of the transformer is correct. This ratio decides what the output voltage of the transformer will be with respect to the input voltage. The ratio is calculated under no-load conditions, with ratios calculated at the tap positions for each winding and for the winding as a whole. A voltage is applied to one winding and the voltmeters connected to both low voltage and high voltage windings are read simultaneously. The transformer ratio is the ratio of the HV voltmeter and the LV voltmeter readings. When ratio tests are being made on three-phase transformers, the ratio is taken on one phase at a time, and the measured ratio should be compared with the ratio calculated using nameplate voltages. Any variation should be within  .5%. Transformer Insulation Resistance Test (Common to all categories)The winding insulation resistance test (also known as the Meggar test) is a measure of quality of insulation within the transformer. It can vary due to moisture content, cleanliness and the temperature of the insulation parts. All measurements are corrected to 20'C for comparison purposes. It is recommended that tank and core are always grounded when this test is performed. Each winding should be short-circuited at the bushing terminals. Resistances  are then measured between each winding and all other windings and ground (for 2 winding transformer - H-LG, L-HG and HL-G and three winding transformer H-LTG, L-HTG, T-HLG, HL-TG, HT-LG, LT- HG and HLT-G ). vPower Factor (Common to all categories)This test is made to monitor the dryness of transformer insulation. Power factor is defined as the ratio of the power dissipated divided by the input volt-ampere multiplied by 100. The measurement of power factor is made with a capacitance bridge and the connections are the same as for the insulation resistance tests. Transformer Resistance (Common to all categories)The resistance of a transformer winding can be measured after current has not passed through the transformer for several hours, allowing it to reach the same temperature as its surroundings. Winding resistance is calculated by measuring the voltage and current simultaneously, with the current as close to the rated current as possible. Calculating the winding resistance can be helpful as it lets you calculate and compensate for I2R losses, a major component of load losses as a whole.  Winding resistance measurements can be made to determine if any changes have occurred in the current carrying path. The winding resistance measurements should be made with a Wheatstone bridge, Kelvin bridge or similar bridge capable of measuring fractional ohms accurately.  For Wye connected values, measurements should be made between each pair of bushings, then summed and multiplied by three-halves to get the comparison value. Transformer Oil Test (Common to all categories)A sample of insulating oil from a transformer in service can reveal much information about what is taking place inside the transformer. There are three basic enemies to insulating oil - oxidation, contamination and excessive temperature. The following tests can be done: Acid number Dielectric breakdown Power factor Moisture content Interfacial tension

After performing the tests the oil can classified as reusable; reusable with minor reconditioning; or disposable. 

Transformer Polarity (Acceptance test)The polarity of a transformer is either additive or subtractive. In order to find out the polarity of a transformer, a voltage is applied between the primary bushings.  If the resultant voltage between the secondary bushings is greater than the applied voltage that means that the transformer has additive polarity.  If it is lower, the transformer has subtractive polarity. Polarity is not important for a single connected distribution transformer, but it is a vital concern if transformers are to be paralleled or bank connected. Three phase transformers are also checked for polarity by the same means. Transformer Phase Relation (Acceptance test)A phase relation test is carried out for polyphase (for instance, three-phase) transformers to make sure that they have been connected in such a way that their phase relationship is correct.  A phase relation test calculates the angular displacement and relative phase sequence of the transformer, and can be carried out in conjunction with ratio and polarity tests.  The voltages of the phase of primary and secondary can be recorded and comparisons made to get the phase relation. Visual Inspection (Periodic and Failure tests)This may reveal either present or potential problems that may not be picked up by diagnostic testing. For example, deteriorating gaskets, low oil level or chipped bushing skirts. A standard list of check points should be established for each unit and then a record of each inspection maintained. Gas/ Gas-in-Oil Test (Failure test):A study of gases either dissolved in the oil or from the gas above the oil can also show abnormal conditions within the transformers, such as incipient faults. Three considerations are very important: The total percentage of combustible gas The percentage of each gas component The rate of change in combustible gas content If the percentage of combustible gases is above 5%, then immediate action is required

The test is performed with a single phase supply with, preferably, a voltage rated at approximately 10% of the phase voltage of the winding to which the supply is to be connected, although lower voltages can be used.
There are 2 methods that can be used: the first is to connect a single-phase supply to any available winding with an ammeter in the circuit to monitor the exciting current.  Three such single-phase tests are necessary for a three-phase transformer. The relationship between the single phase readings is important; it should be as follows:

The readings taken on phase A and C should be within 5% of each other. The reading on phase B should be between 65 and 90% of the readings on phase A and C. Readings that fall outside of the relationships given above may be indicators of a winding fault. In the other method, the same voltage level and ammeter requirements apply except the following connections should be made:
Short one winding on phase C and apply voltage and read the exciting current on phase A.  Short one winding on phase A and apply voltage and read the exciting current on phase C.  Short one winding on phase B and apply voltage and read the exciting current on phase A or phase C. 
Other Transformer Tests:

Other tests which can be performed are:

Core Loss Test Under no-load conditions, a transformer will continue to drain sources of electrical energy. The chief source of this drain is core loss, which occurs in the magnetic core through a combination of hysteresis and eddy current loss, among others.  Core-loss is calculated by applying the rated voltage and frequency to a transformer under no-load conditions.  The resultant current is then measured, from which the loss of energy can be extrapolated. Load Loss Test Load loss is a combination of I2R losses, stray losses and eddy losses, all of which contribute to the loss of electrical energy that is seen as current transferred from one winding to another. Load loss changes with the magnitude of the load: that is to say, higher loads see higher rates of loss.  The load loss is therefore generally calculated for the rated load, while the transformer is under full-load conditions. It can be measured by applying a voltage to one winding while the other winding is short-circuited. The voltage is adjusted until the current flowing through the circuit is the same as the rated current. The power loss measured at this time is the load loss.   Impedance Test Impedance is a measure of the resistance that leads to the loss of electrical energy in a transformer at full load, causing the ratio of the input and output voltages to differ from the Turns Ratio. It can be measured at the same time as load loss. Impedance is found by measuring the voltage required to pass the rated current through one winding of the transformer, while the other winding is short-circuited. This voltage is called the impedance voltage.   Applied Potential Test The applied potential test is used to see how well the transformer's insulation deals with voltages higher than the rated voltage, for given periods of time. The applied potential test checks the insulation between individual windings; and between windings and ground by applying voltages to each of these areas. Induced Potential Test The induced potential test is used to test the quality of the transformer's insulation, as with the applied potential test above. It tests the insulation of the individual windings of the transformer by applying voltages between turns, between layers and between lines.  Quality control impulse test Quality control impulse tests are made on transformers in order to simulate lightning; to see how well they withstand such high bursts of voltage.  The electric impulses applied here can include reduced  full-wave tests, chopped-wave tests and front-of-wave tests, to simulate a range of extreme voltage situations. Pressure Leak Test A transformer can be checked for pressure leaks by pressurizing the tank and then leaving it alone for several hours. If the pressure drops during the intervening time, or if there are signs of liquid leakage, than a leak is present.  Otherwise, the transformer is leakage free. While learning about and overseeing the standard testing procedures of your transformer can be a laborious task, it definitely helps better your understanding of the transformer's operation, minimizes hazard to life and property, reduces downtime, minimizes the chance of sudden failure and thus allows optimum use of the transformer.

Power Transformers Testing

Mike Dickinson began his carrier in transformer industry in 1972 at Pacific Crest Transformers. Currently Mike is in charge of Business Development at PCT. Pacific Crest Transformers is a leader in the design and construction of distribution transformer. Read Trasnsformer testing article and the other Transformer related articles at PCT.

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