Low Voltage Transformers

See also;   ACME Low Voltage Lighting Transformers & Power Supplies, AMVECO Low Voltage Current Transformers, Jefferson Low Voltage End Bell Style Transformers & Hammond Low Voltage Lighting Transformers

Typical low voltage transformers are designed to reduce 120 volt line voltage to a secondary, or output voltage of 12 volts. One of the many uses of low voltage transformer are for landscaping. 

In doing low voltage transformers for landscaping remember the transformer has no way of knowing the line voltage. If simply reduces the current by a factor of 10. So if the line voltage was 115 volts, the secondary voltage would be only 11.5 volts. Conversely, if the line voltage was 130 volts, the transformer would produce 13 volts. Line voltage may vary with time of day and when other electrical loads are on the systems. For this reason is is important to measure the line voltage at the transformer at the same times that the transformer will be in use.

The voltage will decrease the further the current has to travel. In order to compensate for this and the variations in line voltage, some transformers offer several output voltages. These transformers are generally known as multi-tap transformers and may offer voltage outputs ranging from 10 volts to 14 volts. This is accomplished by having leads coming off the primary or secondary coil at various points near the end of the coil to produce several different voltages. This is a valuable feature for a system designer wanting to have better control over light output and lamp life.

There are also buck boost transformers that can be used to change the line voltage a small amount. If you had a situation where the line voltage was typically 110 volts, the landscape lighting transformer would have a normal output of only 11 volts. This reduced output could be offset by using a multi-tap transformer (the 14 volt lug would output 12.8 and the 13 volt lug would have am output of about 11.9) or you could install a 10% boost transformer. You can correct higher than 120 volt situations in the same way by using a buck transformer to reduce the current.

Some companies also offer these transformers to boost voltage on the secondary side. This type of transformer is designed to be buried in the ground as part of the circuit.  The typical boost is 20% to 25%. Therefore if the voltage drop is down to 10 volts at the fixture, installing a booster transformer transformer ahead of the fixture could increase to 12 or more volts.

It is important to understand that transformers can not stabilize voltage variations. They simply transfer the current at a fixed ratio and do not sense changes. There is equipment to handle this problem, but it is typically too expensive and unnecessary for landscape lighting applications.

Low voltage transformers are offered with and without a cabinet. Those without an enclosure are attached to an electrical box and wired directly to the line voltage source.

Transformers that are enclosure are connected to the line voltage source with a standard 6" plug and cord set.  When the transformer is mounted outside the outlet it should be protected by a Ground Fault Circuit  device. The transformer enclosure may be made of plastic, composites, painted steel or stainless steel. The least expensive are plastic models are frequently completely sealed with a single output cable used to connect to the lighting system. Steel cabinets generally open to allow for the use of controls and have electrical screw down lugs to attach the wires from the lighting circuits. If the transformer is multi-tap, there will be several lugs, each marked with the output voltage.

Composites cases are used for direct burial type transformers. These units can be used when the lighting system is at a distance so from the power source that there is a significant voltage drop that cannot be compensated for with larger wire. Because the location is typically away from the structure, it is often convenient to bury the transformer. By running line voltage to the area and connecting it directly to the transformer, the voltage drop is eliminated. When using this type make sure that all installation requirements are met, particularly with  regard to access and drainage.

It should also be noted that not all enclosed transformers are suitable for use indoors. It seems strange because it would have more protection from the weather. but without air it could overheat. Quality transformers are made with protection from over load and short circuit situations. This is an important safety feature. The transformer is protected on the line voltage side by the fuses or breakers in the electrical service panel for the building. But the secondary side of the transformer is not connected to that system. Quality transformers protect the secondary side by running the low voltage through a breaker or fuse.

Low Voltage Transformers should have UL listing for the intended use. It may be listed for indoor use only, outdoor use only, or both indoor and outdoor. Listed products will have the Ul symbol and be marked for the type of use along with a control number on the device.
 

Power Transformer Sources: Power Transformer * Step Up Transformer * Step Down Transformer * Electrical Transformer * Isolation Transformer * Toroidal Transformer * Acme Transformer * High Voltage Transformer * Distribution Transformer * Transformer Manufacturer * Three Phase Transformer * Dry Type Transformer * 3 Phase Transformer * Cast Transformer * Voltage Transformers * Variac * Voltage Stabilizer * Voltage Regulators

 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.

• Starting Capacitor For use with single phase motors and gearmotor applications.
• Run Capacitor For use with 1 and 3 phase motors.
• Start Cap TEMCo offers a wide selection of start caps.
• Air Conditioner Capacitor For use with air conditioners.
• Replacement Capacitor Learn when you need to replace a capacitor and how to pick a new one.
• Motor Capacitor Need help with motor capacitor facts? Check out our FAQ here.
• Test Capacitor Need help with testing a capacitor? Check out our tutorial here.

  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.