Buck Boost Transformers

See also;   ACME Buck Boost Transformers, Hammond Buck Boost Transformers, TEMCo Buck Boost Transformers & Jefferson Buck Boost Transformers

Buck Boost Transformers are small, single phase, transformers designed to reduce (buck) or raise (boost) line voltage from 5 to 20%.

The most common example is boosting 208 volts to 230 volts. usually to operate a 230 volt motor such as an air-conditioner compressor, from a 208 volt supply line.  They have a dual voltage primary and a dual voltage secondary.

Buck-boosts are a standard type of single phase distribution transformers, with primary voltages of 120, 240, or 480 volts and secondary typically of 12, 16, 24, 32 or 48 volts. They are available in sizes usually from 50 volt amperes to 10 kilo-volt amperes.

A buck boost transformer is the ideal solution for changing line voltage by small amounts. The major advantages are their lost cost, compact size and light weight. They are also more efficient and cost less than equivalent isolation transformers. When connected as an autotransformer, they can handle loads up to 20 times the name plate rating.

When a buck boost transformer has the primary and secondary windings connected, it becomes an autotransformer. Now only the secondary windings are transforming voltage and current. The majority of the KVA load passes directly from the supply to the load. This is why they can supply a load with a larger KVA rating than the nameplate indicates.

They are ideal for low voltage lighting control applications. They are designed to supply power to low voltage lighting circuits, control panels or other systems requiring 12, 16, 24, 32 or 48 volts. They are also suited for low voltage landscape lighting. They are UL listed for outdoor service and their compact size makes them the perfect solution for providing power to accent lighting application .

There are two basic types of buck boost transformers, self adjusting (active) or passive designs. The active types monitor incoming voltages and will adjust the outgoing voltage to be within an acceptable range. This is typically between 115 VAC and 225 VAC for computer UPS systems. The system will either lower or boost voltage if it senses a variance in the incoming voltage. 

Passive transformers are used for larger equipment where the amount is fixed. This is commonly used when someone wants to use a piece of equipment that is made for European power (220VAC to 230VAC) in the United States, which has both 208V and 240V service available.

The passive transformers are rated in volt-amperes and are rated for a percent of voltage drop or rise. For example, a buck boost transformer rated at 10% rise at 208VAC will raise incoming voltage of 210VAC to 231VAC. A rating of 5% drop at 240VAC will yield the result of 233VAC if the actual incoming voltage is 245VAC. The ratings of 208VAC for business class three phase power, and 240VAC for residential class electrical power are approximate, and will vary by several volts depending on the location and even the time of day and local demand.

Buck Boost transformers only adjust the voltage, not the frequency, or cycles of the electricity, so you can't use it to adjust equipment that requires 50Hz in the US. All US power plants use a 60Hz systems. Some equipment is designed to run at 50Hz or 60Hz, and would work fine.

Most passive transformers come semi-wired, where you complete the last internal connections to have the unit perform the amount of buck or boost needed. They have multiple taps on both the primary and secondary coils to achieve this flexibility. They are designed for hard wired installations (no Plugs) and allow the same transformer to be used in several different applications. The same transformer can be rewired to raise or lower by 5%, 10%, or 15% for either 208VAC or 240VAC applications, depending on the final wiring done by the electrician.

In the tanning industry (and for use in other industries) there are new fixed transformers that cost about the same but are configured differently. They are already prewired, so you must purchase them with the exact amount of buck or boost you need for your application. Rather than being hard wired units, they have plugs and receptacles making installation very quick and easy.  This eliminates the need for an electrician if you can determine your exact incoming voltage. To further make them easier to use, they offer rating in amps rather than volt amps, which makes it easier to match up the right transformer for the task. These are used almost exclusively in light to moderate applications that require 240VAC 40 amp or less.

Not all 240V equipment needs a transformer to buck or boost the voltage. These types of transformers are used when a piece of electrical equipment has an electrical requirement that is slightly out of tolerance with the incoming power supply. This is most common when using 240V equipment in a business with 208V service or vice versa. It is also common for electronics that are made in a different country than where they are being used.

Often equipment will be rated with a voltage range, such as 220VAC to 230VAC, requiring a buck boost transformer if the incoming power is not within the range. It is important that you use a buck boost transformers that is rated equal to, or greater than the rated load of the equipment, or you can damage the transformer and the equipment.

If a piece of equipment needs a buck boost transformer but one is not used, it can cause damage to the equipment. Running the equipment at a voltage that is lower than the rated amount can cause the amperage load to rise, in order to meet the total wattage requirement of the equipment. This can result in damage, including melting of wires or parts. Running at a voltage too high can cause other types of damage. The type of damage that can happen depends on the type of equipment and it sensitivity to improper voltages, but in most circumstances, it will at least greatly reduce the service life of the equipment and make it more prone to failure. Buck-Boost transformers are an economical way to correct this potentially very serious problem. Anytime a line voltage change in the 5-20% range is required, a buck-boost transformer should be considered as your first line of defense.

When the amount of rise or drop in the incoming voltage is  more than 15% to 20% then this is usually out of the boundaries of what a buck boost transformer is designed for, and a line transformer is required. Line transformers are basically the same, but with different tap points to provide grater rise or drop in voltage, such as 240VAC to 120VAC.

Application Use of Buck-Boost Transformer:

• A typical application is 120 volts in, 12 volts out for low voltage lighting or control circuitry. In most applications, this low voltage transformer is field connected as an auto transformer.
• Low supply voltage exists because equipment is installed at the end of bus system.
• When the supply system is operating at or over its design capacity.
• Where overall consumer demand may be so high the utility cuts back the supply voltage to the consumer causing a "brownout".

These transformers provide tremendous capacity and flexibility in KVA sizes and input/output voltage combinations. Basically you get can get 75 different transformers all in one convenient packaging.

 Most Common Ask Question About Buck-Boost Transformers

1. How does a buck-boost transformer differ from an insulating transformer?

A Buck-Boost transformer is an insulating type transformer when it is shipped from the factory. When it is connected at the job site, a lead wire on the primary is connected to a lead wire on the secondary-thereby changing the transformer's characteristics to those of an autotransformer. The primary and secondary windings are no longer "insulated" and secondary windings are no longer "insulated" and its KVA Capacity is greatly increased.

2. What the different between a buck-boost transformer and an autotransformer?

When a buck-boost transformer primary lead wire and secondary lead wire are connected together electrically, in a recommended voltage bucking or boosting connection, the transformer is an autotransformer. However, if the interconnection between the primary and secondary winding is not made, then the unit is an insulating type transformer.

3. Why do Buck-Boost transformers have 4 windings?

To make them versatile.  A four winding has 2 primary and 2 secondary windings and can be connected eight different ways to provide a multitude of voltage and KVA outputs.

4. Will a buck-boost transformer stabilize voltage ?

NO, the output voltage is a function of the input voltage. If the input voltage varies, then the output voltage will also vary by the same percentage.

5. Are there any restrictions on the type of load that can be operated from a buck-boost Transformers?

There are no restrictions.

6. Why can a buck-boost transformer operate a KVA load many times larger than the KVA rating on its nameplate?

The transformer has been auto-connected in such a way that the 22V secondary voltage is added to the 208V primary voltage, it produces 230V output.

7. Can buck-boost transformers be used on motor loads?

Yes, either single or three phase.

8. Can buck-boost transformers be used on three-phase systems as well as single-phase systems?

Yes, a single unit is used to buck or boost single phase voltage. Two or three units are used to buck or boost three phase voltage. The number of units to be used in a three-phase installation depends on the number of wires in the supply line. If the three-phase supply is 4 wire Y, use three buck-boost transformers. If the 3-phase supply is 3 wire Y (neutral not available) use two buck-boost transformers.

9. Should buck-boost transformers be used to develop a three-phase 4 wire Y circuit from a three-phase 3 wire delta circuit?

No, a three phase wye buck-boost transformer connection should be used only on a 4 wire source of supply. A delta to wye connection does not provide adequate current capacity to accommodate unbalanced currents flowing in the neutral wire of the 3 wire circuit.

10. Why are buck-boost transformers shipped from the factory as insulating transformers and not pre-connected at the factory?

A four winding buck-boost transformer can be connected eight different ways to provide a multitude of voltage and KVA output combinations. The proper transformer connection depends on the user's supply voltage, load voltage and load KVA. It is more feasible for the manufacturer to ship the unit as an insulating transformer and allow the user to connect it on the job site in accordance with the available supply voltage and requirements of his load.

11. Are buck-boost transformers as quiet as standard isolation transformers?

Yes, the isolation transformer would have to be physically larger than the buck-boost transformers, and smaller transformers are quieter than larger one.

12. How does the cost of a buck-boost transformer compare to that of insulating transformer - both capable of handling the same load?

The dollar savings are generally greater than 75% compared to the use of an insulating type distribution transformer for the same application.

13. What is the life expectancy of a buck-boost transformer?

It is the same as the life expectancy of other dry-type transformers.

You should have the following information before selecting a buck-boost transformers:

• Line voltage - The voltage that you want to decrease or increase. This can be found by measuring the supply line voltage with a voltmeter.
• Load Voltage - The voltage at which your equipment is designed to operate. This is listed on the nameplate of the equipment.
• Load KVA or Load Amps - You do not need to know both- one or the other is sufficient for selection purposes. This is usually found on the nameplate of the equipment.
• Frequency - The supply line frequency must be the same as the equipment to be operated - either single or three phase.
   

 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.