Electric transformers are inductively coupled electro-magnetic devices that transfer electrical energy from one circuit to another. All electronically operated equipment depends on power transformers to convert electrical currents into voltages that fit a specific application, and current transformers are also required in order to store and transport energy through power lines and grids.
Because there are so many contexts in which electronic transformation is necessary, there exist a wide variety of electric transformers to accommodate them. Auto transformers, step up and step down transformers, toroidal transformers, zig zag transformers and pulse transformers are just a few examples. By transferring electrical energy through two coil stages, transformers can increase, decrease, isolate, translate and pattern electrical currents to safely power electronic equipment of all voltage requirements. Electric transformer manufacturers configure transformers differently to meet all types of electric transformation applications and range in size from thumb-sized transformers in electric lamps or microphones to the enormous stationary transformers in power facilities. Low voltage transformers convert electrical currents into voltages that fit appliances such as dimmer lights and other small electronic devices, while high voltage transformers are used in the transmission of electricity between power generation facilities and its points of consumption. Most transformers are isolation transformers because they facilitate the transmission of electricity through induction, and many transformers are 3 phase transformers, capable of transforming electricity in 3 phases.
In addition to converting currents to a higher or lower voltage, electric transformers can serve to isolate parts of circuits from others. Auto transformers, however, have no isolation between the source and load circuit; they transmit electricity through conductors that are in contact with each other. An electric transformer can be as large as the fenced-in transformers for whole facilities, or they may be small enough to be tucked away in household appliances such as light fixtures. Electric transformers are necessary when there is a voltage difference between an electronic component or appliance and an electrical power supply. Safety is of the utmost concern in such situations, since using a voltage that is too high or too low to power a device can cause serious problems. Excessive voltage can cause device failure or destruction; in severe cases, over-voltage can cause fires and can expose users to powerful electric shocks. In the case of under-voltage, voltage deficiency can also cause device failure.
Instrument transformers, including current transformers, accurately measure and monitor power voltage as it is transmitted proportionally through the primary and secondary coils. Step down transformers convert higher voltages to lower voltages by having fewer secondary coil windings, while step up transformers' higher number of secondary coil windings allow them to convert lower voltages to higher voltages. Toroidal transformers are donut-shaped transformers that are highly space efficient and excellent for reducing electromagnetic interference; inductors limit the amount of AC flow to an appliance or transient application while suppressing high frequency noise, similar to toroids. Isolation transformers decouple two circuits, allowing AC power to move from one device to another without the two circuits connecting; this is achieved by having the primary and secondary coils not directly connected. Inverters are capable of converting direct current voltage (DC) to alternating current voltage (AC), while pulse transformers create the electrical surges that are used in telecommunication and detail logic applications such as camera flashes, radar equipment and particle acceleration. In addition, zig zag transformers are special-purpose 3-phase transformers that are intended for use in providing earthing for ungrounded electrical systems as well as filtering and controlling harmonic currents.
Electric transformers are comprised of two sets of coils or windings linked by a magnetic field. The core is iron or a ferrite compound or a laminated core wound with bare copper or enameled coils. The coils are primary and secondary and function as conductors. When the primary coil receives AC voltage, this produces a varying magnetic field of voltage surrounding the conductor; the magnetic field activates the secondary conductor coil. This results in the transformers changing the voltage and transferring electrical energy, ideally with the least amount of energy loss. The number of windings on each coil is important, as this determines the voltage that is conveyed from the primary to the secondary through the magnetic field. The ratio of turns (also called windings) in the primary coil to the number of turns in the secondary coil determines the magnitude of the voltage; for example, a step down transformer will have fewer turns in its secondary coil than the primary, while a step up transformer will have more secondary coil windings than primary. Once the voltage conversion is made, the energy is transferred to the load center and the electrical process continues from there. Both the size and expense of electric transformers increases in proportion to the number of primary windings.
Single Phase Transformer - Lenco Electronics, Inc.
Isolation Transformer - Johnson Electric Coil Company
Three Phase Transformer - Lenco Electronics, Inc.
Electric Transformer Manufacturers - Johnson Electric Coil Company
Small Isolation Transformers - Johnson Electric Coil Company
Single and Three Phase Transformers - Johnson Electric Coil Company
Electric transformers have become necessary devices for a range of electrical and electronic components. Their application varies based on the need; thus, numerous types of transformers are available on the market. A single click can populate more than ten types of transformers, and as a buyer, it gets difficult to tell what does what. Therefore, here we are discussing on what bases transformers are classified and what the common types of transformers.
There are close to eleven ways by which electric transformers are classified. The first classification in the history of transformers was of core form or shell form. As they evolved, however, this categorization became less employed.
In the market, the most common parameter for categorizing electric transformers is power capacity; you can find transformers that have capacity of a fraction of a volt-ampere to thousands of volt-amperes.
The second most common way is duty, in this category, you can find transformers designated as short-time, continuous, periodic and intermittent, including others. The other parameter is the range of frequency; you can transform with audio, radio and power frequency. Just like power, transformers are also classified based on voltage, which range from a single volt (low voltage transformers) to thousands of volts.
Moreover, electric transformers are categorized on the basis of the cooling system it has; the categorization goes further to application, as there are isolation transformers and impedance transformers.
Similarly, transformers are categorized on the basis of coiling configuration; under this parameter, you can find delta, star and Zig Zag transformers. Auto transformers are also categorized by this parameter.
We will now discuss some popular transformers, so you can understand what they are.
Zig Zag transformers
This type of electric transformer is used for grounding circuits, and is employed when three wires are involved. The transformer, basically, creates the neutral. This transformer got its name from its winding configuration, which has nothing to do with its application.
It is hard to tell how this transformer got its name; however, it is no way an automated device. Instead, it has peculiar construction, which varies wildly from a traditional transformer. It does not have separate primary and secondary coils but one, which functions as both. The ingenious design makes the transformer a lot smaller, as well as efficient and manages voltage better than other alternatives.
It is easy to tell why they are called leakage transformers, they leak magnetic induction. To many, the working seems odd-given efforts are always made to cut the leakage, so why use a leaking device? The answer lies in the application. They are used in welding and in high-voltage lamps. To reduce the voltage, they are deliberately fabricated with loose winding that leaks the induction.
These are the most common transformer used for distribution of power. They usually transmit power from the generation source to the distribution center. These types of transformers are efficient but costly, as only high-quality metals are used.
Electric transformers are ubiquitously employed in an array of electrical and electronic components, as they are an essential device in almost every circuit. Power transformers have played a big role in making alternating available widely, and for transmission, distribution and isolation. For isolation purposes, isolation transformers are employed. With its evolution spanning over 200 years, it has evolved in various sizes, ranging from cubic centimeter to multiple tons.
Electric transformers transform the voltage up or down, based on the need. To change the voltage, it employs Faraday's law of induction, which was conceptualized in 1831, and defines the behavior of electromagnetic induction. It took more than 60 years to make a working model of transformer that can make use of this principle. That said, let us move on to how modern transformers work.
The first step in understanding the working process of electric transformers is the construction. A standard transformer typically consists of two coils: the primary coil and the secondary coil. The coils are disconnected and do not have any electrical conductor between them. However, the coils are wrapped around a core which is made from different magnetically permeable metals, which means the core shows resistance to the movement of the magnetic field and conducts it freely. However, that only happens in theory. In reality, there are losses involved.
A source of varying alternating current is connected to the primary winding, and when the current flows through the hollow coil, strong magnetic fields of varying degrees are produced, also known as magnetic flux. When the core is exposed to magnetic flux, it also is magnetized. There is no electrical conductor but a magnetic permeable material that connects two coils. Due to the magnetic induction, the magnetic field produced in the core is passed on to the secondary coil. Therefore, as the varying magnetic fields are produced in the secondary coil, it induces varying voltage. To induce a varying voltage in the secondary coil, the primary coil should be connected to varying alternative current source. The resulting voltage in the secondary coil can be set with a use of load impedance for a suitable application.
In this article, we did not discuss any loss of energy, as it is how an ideal electric transformer works. However, in a real electric transformer, there are number of losses. The losses include coil losses, hysteresis loss, Eddy current loss and stray loss.
In coil losses, the energy is lost in the form of heat because of resistance in the wire used in the construction of transformers. Hysteresis losses also occur in the form of heat, however, within the core when the magnetic field is reversed. Similarly, Eddy current also causes losses because of the resistance. Finally, the stray losses, as the name implies, occur at various places because of inefficient design.
Electric transformers, basically, consist of two elements: a magnetically permeable core and windings. In traditional transformers, there are two coils or windings, known as the primary and secondary coil. The primary coil is connected to a source of varying alternating current, and as the current flows through the coil, magnetic field is produced. Due to electromagnetic induction, the core gets magnetized, which is called magnetic flux. The magnetic flux created in the core induces electromotive force or voltage in the secondary coil. That is how electric transformer works; an important thing to observe in the operation is that all three elements, the primary and secondary coils, and the core are not connected to each other through an electrical conductor, but through magnetic induction, which move from the primary coil to core and then to the secondary coil, resulting in voltage.
Typically four types of cores are used for different applications: laminated steel core, solid cores, toroidal core, as in toroidal transformers, and air core.
Laminated steel cores, also known as silicon steel, are specially fabricated for transformers, since steel enables great magnetic permeability. The high permeability is important to cut the magnetizing current and direct the magnetic flux into the coil. Unlike the old designs, when cores were made with solid iron that promoted Eddy currents, a type of loss, laminated steel confines eddy currents to a region that do not interfere with magnetic flux, giving high efficiency to electric transformers. There are typically two types of laminated steel cores: EI and C; EI type has E shaped steel, which are capped from I type steel, whereas in C types, steel is fabricated in a C shape. These types of cores are usually installed in power transformers.
This type of core, as the name implies, has a solid core, however, not like the old solid iron cores. To allow high magnetic permeability and cut eddy currents, powdered iron is used to make the core. This type of transformer is made specifically for radio-frequency transformers. Some variations, such as ferrites, are also found in solid cores instead of iron powder. Movable cores are also fabricated for radio applications.
The core, as the name suggests, is in the shape of toroid, meaning ring shaped. For different needs, ferrites, powdered iron, silicon steel, and alloys are used to make a circular core. The design reduces the losses and improves efficiency, however, they have a limited capacity. Even though they reduce the loss and have a cache of advantages compared to EI steel cores, they are cheaper than silicon steel EI cores. The electric transformers that use this type of core are called toroidal transformers.
For radio applications, a special type of core is used, which consist of nothing but air. Practically, there is no need of core to pass on the magnetic flux, if two coils are brought together, the transformer works, however, with some losses, making them unsuitable for electrical installations.
Electric Transformer Terms
- A transformer that uses air to cool by use of fans or normal ventilation.
- A transformer with one winding per phase.
- Describes multiple single phase transformers connected together to provide power to a three phase load.
central part or inductor that enhances the power of the magnetic field.
- In a three phase connection the windings all connect to form a loop.
of time for a transformer to provide full rated power to the load. This
measurement greatly affects the actual size of the transformer.
Encapsulated - A dry transformer with an enclosed core and coil assembly.
amount of current a transformer draws at nominal voltage input in an
- A conductor that can handle thermal expansion and contraction as well as reduce noise.
the forces that resist the flow of current in AC circuits like resistance
or inductive or capacitive reactance.
- Kilovolt Ampere rating that is a measurement of the output of a transformer without exceeding a certain temperature.
- The quantity of
electric power supplied or necessitated at any particular spot in the
system. Also a requirement of the KVA or
VA from the transformer; light bulbs are loads.
- The direction of the current between two leads. If the directions are the same, the leads have the same polarity. In electric transformers the polarity is classified as either additive or subtractive.
divided by volt amps, KW divided by KVA - the leading and lagging
of voltage versus current caused by inductive or capacitive
loads. Harmonic power factor relates to nonlinear current.
- On the load or output side, the connected transformer winding.
- Pressure switch device that detaches the transformer from the line.
- The measurement of the amount of force on a unit charge because of the surrounding charges.
- The change, in percentages, of the output voltage from no load
to full load.