BASES PARA EL DISEÑO DE TRANSFORMADORES ELECTRICOS (EN INGLES)

Custom Transformers

Despite the many different categories and specifications of transformers, it is sometimes necessary to use a custom transformer to ensure the best results. Custom transformers are usually required when a transformer needs to be able to perform special functions or requires unusual features. If untraditional construction, rare material, or high voltage coils are involved, a custom transformer may be the safest option to pursue.

There are several common problems and requisites that custom transformers can offer potential solution for, including:

• Unusual input or output voltage
• Line and load reactors are essential parts of regeneration and power factor control
• Protective enclosures are needed
• Ripple filters and armature chokes are required to reduce DC drive noise
• Unusual wiring

When in the market for a custom transformer there are several things a manufacturer should be able to provide, as well as several key pieces of information to keep in mind.

1. A positive relationship with the design and engineering staff can help guarantee efficient and effective product manufacturing, by ensuring important concerns are being addressed
2. The engineer and design team should be able to design a new part, and alter or replicate and already existent one.
   
3. Make sure that when using CAD for prototypes or for designing a solution they are able to offer you service while also keeping cost reasonable.
4. When negotiating price, a quote should be available within three days to one week, depending on the specific complexities of the transformer. Attempts should be made to respond appropriately to requests for a faster quote.
5. Development of a prototype can usually be completed within a few days. Appropriate software (CAD, for example) should ensure that the prototype is dimensionally accurate.
6. An effective manufacture should be able to provide a wealth of options when it comes to concepts, materials, and technology, and should be up to speed with recent developments and trends.
7. In terms of price, an aluminum wound core is more affordable, but copper is more energy efficient and can save money spent on electricity. Additionally, copper is strong and highly corrosion resistant, meaning it can outlast aluminum, and connections remain nice and tight.
8. A transformer with an oval shape wound core (as opposed to the traditional square core) can help reduce core loss by ensuring the flux moves in the same direction as the grain.
9. A certain amount of noise can be expected with all transformers, and is produced by the flux of the core. A manufacturer should present sounds levels that match the standards of the American National Standards Institute and are subsequently certified. Anti-vibration isolators are also a good way to help minimize the transformer hum.
10. A transformer should be designed to achieve a temperature within the appropriate range for the type of insulation. Not only does this help a transformer reach its maximum lifespan, it can also prompt other design issues to be considered before manufacturing actually begins.

When it comes to selecting a manufacturer for custom transformers, these tips are only the beginning. With every specific transformer considerations are likely to be different. Regardless, it is also helpful to do some background work on the manufacturing company, to make sure they have a legitimate reputation and can provide appropriate results. The “Better Business Bureau” may be a helpful resource in the vetting process, as well as a place to consider looking for alternative options if the occasion arises.

General Types of Transformers

Transformers are more than just extraterrestrial robots—they’re also highly useful devices for transferring energy between circuits. By using inductively coupled electrical conductors as the main agent of transfer, a change in current in the first circuit is carried over to the second circuit, which subsequently assumes the new charge. Each end of the circuit carries the charge within a winding—either primary or secondary—which is constituted of electrically conductive wire wound around opposite ends of the transformer core, which has high magnetic permeability, making the transfer possible.

In an ideal situation, the change in voltage is proportional, with the second circuit receiving voltage in relation to the number of turns in the primary winding. The voltage is therefore manipulated by altering the number of turns in the primary winding to be larger or smaller than the number of turns in the secondary winding, which either increases or decreases the amount of electricity received. 

Transformers are essential when it comes to the national power grid and are responsible for transmitting large amounts of high voltage power over long distances. This is not to say that all transformers are large—they come in many different sizes—and some are certainly not designed for high levels of output. Depending on the intended function and the amount of power needed, transformers can be as small as a fingernail or weigh several hundred tons. 

Common Types of Transformers

Autotransformers

Autotransformers are different from traditional transformers because autotransformers share a common winding. On each end of the transformer core is an end terminal for the winding, but there is also a second winding that connects at a key intermediary point, forming a third terminal. The first and second terminals conduct the primary voltage, while the third terminal works alongside either the first or second terminal to provide a secondary form of voltage. The first and second terminals have many matching turns in the winding. Voltage is the same for each turn in the first and second terminal. An adaptable autotransformer is another option for this process. By uncovering part of the second winding and using a sliding brush as the second terminal, the number of turns can be varied, thus altering voltage (see image on right).

Polyphase Transformers

This type of transformer is commonly associated with three phase electric power, which is a common method of transmitting large amounts of high voltage power, such as the national power grid. In this system, three separate wires carry alternating currents of the same frequency, but they reach their peak at different times, thus resulting in a continuous power flow. Occasionally these “three-phase” systems have a neutral wire, depending on the application. Other times, all three phases can be incorporated into one, multiphase transformer. This would require the unification and connection of magnetic circuits so as to encompass the three-phase transmission. Winding patterns can vary and so can the phases of a polyphase transformer.

Leakage Transformer

Leakage transformers have a loose binding between the primary and secondary winding, which leads to a large increase in the amount of inductance leakage. All currents are kept low with leakage transformers, which helps prevent overload. They are useful in applications such as arc welding and certain high-voltage lamps, as well as in the extremely low-voltage applications found in some children’s toys.

Resonant Transformer

As a type of leakage transformer, resonant transformers depend on the loose pairing of the primary and secondary winding, and on external capacitors to work in combination with the second winding. They can effectively transmit high voltages, and are useful in recovering data from certain radio wave frequency levels.

Audio Transformer

Originally found in early telephone systems, audio transformers help isolate potential interference and send one signal through multiple electrical circuits. Modern telephone systems still use audio transformers, but they are also found in audio systems where they transmit analog signals between systems. Because these transformers can serve multiple functions, such as preventing interference, splitting a signal, or combining signals, they are found in numerous applications. Amplifiers, loudspeakers, and microphones all depend on audio transformers in order to properly perform.

Isolation, Zigzag, Pulse, and Speaker Transformers

In addition to commonly used transformers, such as polyphase and resonant transformers, there is a whole field of other more specific types. Among them are isolation, zigzag, pulse, and speaker transformers.

Isolation Transformers

Although most transformers rely on the connection between windings which enables power to be transferred, isolation transformers are substantially different. In an insulation transformer, the primary and secondary windings are isolated from one another by insulation. This separation allows for an AC voltage to be transferred from one circuit to another while blocking DC signals and interference associated with ground loops. Generally speaking, isolation transformers are effective at power transfer in sensitive applications, such as computers and laboratory equipment. Hospital Grade isolation transformers can help protect sensitive equipment in medical environments.

Isolation transformers serve many unique functions that other transformers do not offer. For example, an isolation transformer can use the primary and secondary windings to increase or decrease the output, which makes it well suited to circuits with varying voltage loads. Additionally, isolation transformers can include Faraday shields, which lessen high frequency noise, improve power, and lower leakage currents.

Traditional transformers consist of primary and secondary windings around a core, and occasionally include a Faraday shield between windings to help reduce noise. Without a Faraday shield present, a fair amount of capacitance noise occurs between the windings.

Zigzag Transformers

Zigzag transformers have a primary winding but lack a secondary winding. Because they fall under the category of three-phase transformers, there are six coils on three separate cores. On each core, the first coil connects in a zigzag pattern to the second coil on the next core. Then, the second coils are joined and connected to the primary coils, comprising a neutral. Because the phases couple, the voltages cancel out, enabling the neutral pole to be secured to the ground. They resemble a Y transformer, whose neutral point is grounded. If one phases fluxes, all other phases are thrown out of balance; the zigzag formation, however, provides a path for earth faults (or zero sequence) to exit. Zigzag transformers are often applied to ungrounded electrical systems to derive a reference point.

Pulse Transformer

When it comes to transmitting a pulse with a fast rise and fall time, pulse transformers are optimal because they are specially designed for handling this type of electrical transfer. Because many different kinds of applications exhibit this type of pulse pattern (also known as rectangular electrical pulses), pulse transmitters can be made in a range of sizes to effectively handle a change in voltage magnitude. For smaller applications, pulse transformers called signal types are preferred, and are commonly used in applications such as telecommunications circuits. Medium-sized models are used for applications like camera flash controllers, whereas larger models play an important role in the power distribution industry. 

Speaker Transformers

Speaker transformers are a type of electrical transformer that can power multiple loudspeakers with one circuit, as long as the circuit is performing at higher than normal voltage. They are referred to as constant volt or 70 volt speakers, despite the fact that the voltage is constantly changing. In terms of audio engineering, audio transformers can act as amplifiers by helping increase low-voltage output to the speaker circuit. At each speaker, an even smaller transformer alters the voltage and impedance, bringing them back up to standard speaker levels. The volume of each speaker can often be readjusted as needed. Using high-voltage and impedance speaker transformers minimizes power loss. All pulse transformers have a cycle of less than one; this means that at the end of the cycle any energy left in the coil must be disposed of before the pulse can run again.