GE Ventilated Dry-Type Transformers

Features and Benefits
Factory NEMA 3R option is available
Standard product offering is wound with Aluminum conductor. Copper is available as an alternative on many designs.
Non standard voltage designs can be created to meet individual customers needs.
Applications
Step Down Incoming Distribution Voltages
Product Scope
Voltages up to 600V
Confirms to ANSI and NEMA standards
Single phase is offered in ratings 25 to 333 KVA.
Three phase is offered in ratings 15 to 500 KVA
Standard BIL levels of 30 and 60 can be increased on many ratings to 60 and 95 KV BIL.

THE WHYS OF THE WYES

An introduction to the behavior of transformer Y connections

The earliest transformers were of course single phase, connected directly across the two supply lines. With the advent of the three-phase system, two alternative methods of connection for transformers were offered-the delta fashion as the more obvious one based on the singe-phase practice, and the Y fashion as an intriguing new possibility. Somebody must have been thrilled to discover that the Y connection works, and that if one wished to be different, he could even connect one side of the transformer in Y, and to other in delta. The Y connection must have appealed to the operators then, as it does now, because it provides two different values of secondary voltage instead of one, and it makes it possible to ground all three phases symmetrically at a common point.

Problems of the Y-Y Connection

It didn't take the industry long to discover one problem after another arising out of the Y-Y connection with the primary neutral floating.

The first problem discovered was that in three-phase banks of single-phase units and in three-phase shell type units, although the line voltages conformed to turn ratio, the line-to-neutral voltages were not 58% of the line voltages but about 68% at no load and diminished very rapidly when the bank was progressively loaded line to neutral.

Oscillographic studies showed that with sine-wave voltages between lines, the line to neutral voltages of these banks had about 60% third harmonic component. This explained the overvoltage at no load, because, as the effective values of voltages at different frequencies combine at right angles.

The large voltage regulation of these banks for unbalanced line to neutral loads was discovered to be due to the fact that, whereas line-to-line loads cause a voltage regulation through the ordinary leakage impedance of the bank, the line-to -neutral loads caused a voltage regulation through their magnetizing reactance which is generally 100-1000 times as large as the leakage reactance.

The three-phase units with three-legged cores were found to behave quite differently in these matters. Their third harmonic voltage were negligible (according the the standards of those days), and the line to neutral voltages were practically 58%, and their voltage regulation for loads to the neutral, though poor, we not altogether intolerable.

In present day language, a balanced three-phase line-to-line load causes voltage regulation through the positive phase sequence leakage impedance X of the bank; and al line to neutral load through a combination of the positive and zero sequence impedances of the banks. In three-phase banks of single-phase units and in shell-type three-phase units, the X is the same as the magnetizing impedance, and therefore such banks were altogether unsuitable for neutral loading. However, in small three-legged core type units, X was found to be of the order of 50%-100%, and such units could handle small high power factor line-to-neutral loads where the quality of the service (constancy of voltage) was not very high grade.

Around 1910 the industry thought that it understood the Y-Y connection well enough so as not to make a misapplication of it. An operator had a shell-type Y-connected autotransformer on his ungrounded neutral system. He knew enough not to expect to load it to neutral , but one day he wanted to ground the neutral and could see no harm in it. That 68% leg voltage (instead of the proper 58%) could not hurt the insulation of the lines or bushings in any way. So he closed the neutral to ground. The lines flashed and the breakers opened to the amazement of the operator. The trouble was traced to series resonance between the third-harmonic magnetizing reactance of the transformer and the line capacitance to ground.

Although the third harmonic phenomena are more spectacular, yet Y connection has also improtant 60-cycle problems and also impulse problems which would be well for an operator to understand. So, we will discuss in easy stages such matters as these:

In connection with the third harmonic, why third harmonic problems and not other harmonics also; how to estimate the resonance condition; the effects of the secondary (or tertiary) delta winding; reactance and size of a tertiary delta winding; the tree-legged three-phase core as the equivalent of a high reactance tertiary delta winding; residual third harmonic.

In connection with 60-cycle problems, we may discuss the various uses of the neutral; the requirements for satisfactory loading; the requirements for satisfactory grounding; inversion phenomena in auto-transformers.

In connection with transient phenomena, impulse voltage behavior of windings: differences between Y and delta; the problems  of the autotransformer, and so forth.

• GE Control Power Transformers

• GE Commercial Pad-Mounted Transformers

• GE Commercial Pole-Mounted Transformers

• GE Ventilated Dry-Type Transformers

• GE Substation Transformers

• GE Construction Non-ventilated Transformers

• GE Current Transformers

 Power Transformer Information:

 Power Transformer Manufacturer

• ACME Transformers - With Acme Electric being in business over 80 years, they have always believed in offering there customers superior service, quality and technical expertise in the transformer market.
• AMVECO Transformers - AMVECO designs and manufactures toroids transformers, current transformers, and auto transformers. Most AMVECO products are custom designed utilizing their state-of-art proprietary CAD programs.  The AMVECO engineers can quickly generate designs in a matter of hours, if needed.
• Federal Pacific Transformers -  Federal Pacific is a division of Electro- Mechanical Corporation, a privately held, American owned company founded in 1958. Federal pacific offers dry-type transformers from .050 KVA through 10,000 KVA single and three phase, up to 34.5 KV, 150 KV BIL with UL approval through 15 KV.
• Marcus Transformer - Ever since they opened their doors for business a half a century ago, they have been a leader in innovative transformer design. As a family-owned company they are proud of the reputation they have earned for making quality-built transformers that deliver exceptional performance and savings.
• Hammond Transformers -  Hammond Manufacturing was founded in 1917 in Guelph, Ontario, Canada. In the last 3 decades it has expanded to the US and the international markets offering many types of power transformers. 
• TEMCo Transformers - TEMCo Transformer, a family-owned business which has been manufacturing and distributing electrical products since 1968. They focus on transformers that significantly reduce power consumption over 30 percent compared to competitive makes.
• GE Transformers - GE has been a key player in the energy industry for more than a century.  Since the installation of their first steam turbine in 1901. They have become number one provider of high-technology power generation and distribution equipment.
• Jefferson Electric Transformers - Jefferson Electric has been a pioneer and innovator of magnetic products since 1915. Jefferson broad line of dry-type transformers are backed by quality assurance systems so stringent that each and every unit gets thoroughly tested before it goes out there door.
• More power transformer brands - Check out more companies by clinking this link.

 Power Transformer Types

• Distribution Transformers - Distribution transformers are generally used in electrical power distribution and transmission power. This class of transformer has the highest power, or volt-ampere ratings. and the highest continuous  voltage rating.
• Substation Transformers - Substation Transformers are large devices which usually weigh tens of thousands of pounds.   They are filled with tens of thousands of gallons of heat transfer fluid.  Although they are typically 99.8% efficient in the transforming of electricity from one voltage to another, processing hundreds of Mega Volts-Amps of electricity force the liberation of hundreds of BTUs per second.
• Medical Grade Isolation
   Transformer - Medical Grade Transformers generally refer to the transformers used in medical devices as well as hospital, biomedical and patient care equipment. There are a number of strict safety rules, guidelines and laws governing the design, construction and the test of these transformers.
• Drive Isolation Transformer - They are used to isolate a drive from a main power line to prevent the transmission of harmonics that the drives produce back into the power line.  They stop drive harmonics from disrupting computers and other sensitive equipment.
• Toroidal Transformers - Toroidal Transformers are more efficient than the cheaper laminated EI types of similar power level. Some of the advantages are smaller size, lower weight, less mechanical hum, (making them superior in audio amplifier), low-off-load loss.

 Power Transformer Types

• Step-Up Transformers - A Step-Up Transformer is one whose secondary voltage is greater than its primary voltage.  This kind of transformer "steps up" the voltage applied to it. -
• Step-Down Transformers - A Step-Down Transformer is  designed to reduce voltage from primary to secondary.  They can range from sizes from .05 KVA to 500 KVA
• Isolation Transformers - An Isolation Transformer is a device that transfers energy from the alternating current (AC) supply to an electrical or electronic load.  It isolates the windings to prevent transmitting certain types of harmonics.
• Buck Boost Transformers - Buck Boost Transformers make small adjustments to the incoming voltage. They are often used to change voltage from 208v to 240v for lighting applications.  Major advantages of Buck boost transformers include; low cost, compact size and light weight. 
• High Voltage Transformer - There are many different types of voltage transformers. A High Voltage Transformer operates with high voltages. Typically, these voltage transformers are used in power transmission applications, where voltages are high enough to present a safety hazard.
• Medium Voltage Transformers - A Medium Voltage Transformer can be connected directly to a primary distribution circuit and generally has the most load diversity. These voltage transformers have installation practices that are generally in accordance with application recommendations from the Institute of Electrical and Electronic Engineers (IEEE).
• Low Voltage Transformers - A Low Voltage Transformer is an electrical device that transforms 120 volts (line voltage) into 12 volts or 24 volts (low voltage). Some uses for low voltage transformer are in landscaping lighting.
• Single Phase Transformers - In electrical engineering, single-phase electric power refers to the distribution of electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors.
• Three Phase Transformers - Three Phase Transformers must have 3 coils or windings connected in the proper sequence in order to match the incoming power and therefore transform the power company voltage to the level of voltage needed while maintaining the proper phasing or polarity.
• Custom Transformers - Custom Transformers are designed for a certain performance specifications and size requirements.  The company works with your engineering specification. 
• Industrial Control Transformers - Industrial Control Transformers are used to convert the available supply voltage to the required voltage to supply industrial control circuits and motor control loads.
• Pad Mounted Transformers - Pad Mounted Transformers are usually single phase, or three phase, and used where safety is a main concern. Typical applications; restaurant, commercial building, shopping mall, institutional. 
• Pole Mounted Transformers - Pole Mounted Transformers are used for distribution in areas with overhead primary lines. Outside a typical house one can see one of these devices mounted on the top of an electrical pole.
• Oil Filled Transformers - Oil Filled Transformers are transformers that use insulating oil as insulating materials.  The oil helps cool the transformer. Because it also provides part of the electrical insulation between internal live parts, transformer oil must remain stable at high temperatures over an extended period.
• Dry Type Transformers - Dry-Type Transformers are available for voltages up through 34.5 kV (although the most common upper limit is 15) and KVA ratings up through 10,000 (with 5000 as the usual limit). Dry-type use air as a coolant, lowering health and environmentally concerns.
• Auto Transformers - An Autotransformer is an electrical transformer with only one winding. The winding has at least three electrical connection points called taps. Autotransformers are frequently used in power applications to interconnect systems operating at different voltage classes, for example 138 kV to 66 kV for transmission. Another application is in industry to adapt machinery built for 480 V supplies to operate on the local 600 V supply.
• More power transformer types - Read further about additional transformer types and their uses.

 Power Transformer Term Definitions

• Electrical Transformers - Electrical Transformers are devices used to raise or lower the voltage of alternating current. For instance, power is transported over long distance in high voltage power lines and then transformers lower the voltage so that the power can be used by a business or household.
• Isolating Transformers - An Isolating Transformer is a transformer, often with symmetrical windings, which is used to decouple two circuits.  An Isolation transformer allows an AC signal or power to be taken from one device and fed into another without electrically connecting the two circuits. Isolation transformers block transmission of DC signals from one circuit to the other, but allow AC signals to pass. 
• Transmission Power Lines - A Transmission Line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic or acoustic waves as well as electric power transmission. Components of transmission lines include wires, coaxial cables,  dielectric slabs, option fibers, electric power lines, and waveguides.
• Transformer Voltage - The measure of the amount of force on a unit charge because of the surrounding charge.
• Transformer Phase - Most transformer are either single phase or three phase.
• Transformer Frequency - The transformer cannot change the frequency of the supply. If the supply is 60 hertz, the output will also be 60 hertz.
• Transformer K Factor - Some transformers are now being offered with a k-factor rating. This measure the transformer's ability to withstand the heating effects of non-sinusoidal harmonic currents produced by much of today's electronic equipment and certain electrical equipment.
• Primary Voltage - The coil winding that is directly connected to the input power.
• Secondary Voltage - The coil winding  supplying the output voltage.
• Harmonic Cancellation - Harmonic cancellation is performed with harmonic canceling transformers also known as phase-shifting transformers. A harmonic canceling transformer is a relatively new power quality product for mitigating harmonic problems in electrical distribution systems. This type of transformer has patented built-in electromagnetic technology designed to remove high neutral current and the most harmful harmonics from the 3rd through 21st.
• Weatherproof - Enclosed transformers come with a weatherproof standard set by NEMA.
• Epoxy Encapsulated - A process in which a transformer or one of its components is completely sealed with epoxy or a similar material. This process is normally preferred when a unit might encounter harsh environmental conditions.
• More power transformer terms - Such as inductor, ground fault, core saturation, current transformer, faraday shield, etc.

Related Transformer Products

• Voltage Regulators - A Voltage Regulator is an electrical regulator designed to automatically maintain a constant voltage level.  It may use an electromechanical mechanism, or passive or active electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.
• AC Line Reactor - AC Line Reactors is a three phase transformer used in conjunction with AC variable frequency and DC motor drive. They are a bi-directional protective filtering device.
• Line Power Conditioners - Power or Line Conditioners regulate, filter, and suppress noise in AC power for sensitive computer and other solid state equipment.
• DC Power Supplies - Conversion of one form of electrical power to another desired form and voltage. This typically involves converting 120 or 240 volt AC supplied by a utility company to a well-regulated lower voltage DC for electronic devices.
• Rotary Phase Converters - Rotary Phase Converters are commonly used in home or small commercial or industrial settings. Rotary phase converters convert single-phase power into three-phase power. This is a very cost-effective way to power three-phase electric motors and other three phase equipment.
• Frequency Converters - A Frequency Changer or Frequency Converter is an electronic device that converts alternating current (AC) of one frequency to alternating current of another frequency.
• Voltage Converters - A Voltage Converter changes the voltage of an electrical power source and is usually combined with other components to create a power supply.
• Magnetic Motor Starters - Magnetic Motor Starters are essentially heavy duty relays mounted in boxes, often equipped with heater/thermal overloads matched to the motor they start.
• Motor Starting Auto Transformers - An Auto Transformer starter uses an auto transformer to reduce the voltage applied to a motor during start. The auto transformer may have a number of output taps and be set-up to provide a single stage starter, or a multistage starter.

For an additional resource the Best of Industry Web Directory : Electrical Power Transformer Directory section is quite useful.