Which Transformer Does What?

Need a transformer? It helps to understand a bit about these devices before you go ahead and buy one. They’re diverse, flexible and eminently useful and among the most common components in use in all fields of technology.

What Are Transformers?

Transformers are among the most basic of all electronic equipment. They make it possible for appliances and other technologies that have different voltage requirements to run off of the same source of voltage, stepping that voltage up or down to match the specifications of whatever device is hooked up to the power mains. These devices are seen everywhere, from inside the large plugs that serve as adapters for routers and other products to hanging off of the side of utility poles in the form of large cylinders. There are many different types of transformers out there, each with its own specialized purpose and its own features.

In more technical terms, a transformer uses inductive principles to transfer energy in the form of electricity. This is done via the transformer’s coils, their most important part.

History of Transformers

There are several people who played significant roles in the development of the transformer. Most of this development took place around the mid-to-late-19th Century, an era where a lot of invention was taking place in the world of electricity. The first transformer suited for commercial use was developed by William Stanley in 1886, who was working for Westinghouse, principal rival to Edison. Since the invention of that first commercial transformer, it has been a vital component in most electrical applications. Not only did Stanley create a transformer that was suitable for commercial use, he also made it suitable for mass production.

Transformers work on a principle called induction. This was first discovered in the 1830s by two men, Michael Faraday and Joseph Henry. Faraday’s name you may remember as a metric used in electronics analysis. He was a significant name in the scientific research that led to the modern, electrified, age.

Today, transformers are among the most common electrical equipment in the world. They can be large or small, handle the voltage needs of an array of different appliances and technologies, and are very inexpensive to produce. They really are among the most important pieces of technology in the world and have been continually improved upon and developed since they were first brought onto the market.

What Are Transformers Used For?

Given that they’re not new technology and are so common, it’s easy to not realize just how amazing transformers are. They can step voltage up or down, increase or decrease current and alter electrical energy in many different ways. By way of an analogy, it’s easier to understand how powerful this is.

Imagine if you had a vehicle that could increase or decrease the total horsepower available based on need, simply because it had a very inexpensive, easy to produce part attached to the engine. Cruising down a flat road? Reduce the power and save gas. Going up a hill? Turn it into a vehicle with the horsepower of a semi. In a way, that’s what a transformer does.

Transformers are usually not visible in the appliances and products they use. For instance, if you were to take apart the power supply on your computer, you’d find a transformer. That transformer takes the wall current, which comes in at 120 volts, and steps it down until the connectors supply the 12- and 5-volt power your computer needs to function.

If you look at most wall adapters, you’ll find a transformer underneath the large housing that you plug into the wall. In many electrical appliances, the transformer is in the casing of the device itself.

Transformers are also used to step down the voltage for appliances that are purchased in one nation and brought to another. For instance, if you bought an electric razor in the US, it would be designed to run on 120V, the standard US wall voltage. If you went to Europe, where most wall voltages are 220V, you would have to step the voltage down to 120V, using a transformer.

The Basic Principle of Transformers

A transformer works on the principle of induction. This is one of the simpler electrical concepts to understand. When you run a current through the primary coil in a transformer, a magnetic field is produced. The magnetic field is then passed through the core and induces voltage and electrical current in the secondary coil. It’s very simple and the actual amount of voltage produced in the secondary coil can be determined by using Faraday’s Law.

This simple principle makes it possible for people to turn on their lights, run their computer, toast their bread and do everything else that house mains make possible, starting with the same amount of electrical power and stepping it down as needed.

What Are the Classification Parameters of Transformers?

Several different parameters are used to classify transformers. They include:

  • Duty: This can be varying, intermittent, periodic, varying, short-time, and continuous.
  • Cooling Type: Forced air, liquid immersed, forced oil, water-cooled, dry and self-cooled
  • Voltage Class
  • Circuit Application: The role of the transformer in the circuit, such as matching impedance, voltage, isolation, and so forth
  • Constant-potential transformer descriptor: This described whether the transformer is a step-up, step-down or isolation device
  • Winding Configuration: There are several different winding configurations, including wye, star, delta, zigzag and more
  • Rectifier phase-shifting Winding Configuration; Includes n-winding, 6-pulse, 12-pulse and more
  • Utilization: The actual purpose of a transformer
  • Power Capacity: Transformers can handle a huge range of power between the different types available
  • Basic Magnetic Form: Describes the way magnetism is handled, including shell and core forms.

Types of Transformers:

  • Audio Transformers: These transformers are found in speakers and other audio equipment.
  • Auto transformers: Transformers that are designed with a common winding for the primary and secondary circuit with widespread applications
  • Chassis Mounting Transformers: Transformers supplied with a mounting device attached for chassis.
  • Chip Baluns: A type of impedance transformer used in electronics. It converts balanced loads to unbalanced loads.
  • Coil Formers: Small transformers that are easily mounted in electronic devices with widespread usage.
  • Current Transformers: Transformers that alter the current in a circuit, used whenever it needs to be stepped up or down, common in meters and relays.
  • DIN Rail & Panel Mount Transformers: A mounting system used on a variety of different transformers.
  • LAN Ethernet Transformers: Used for transmitting Ethernet data standards over copper lines.
  • Lighting Transformers: These are typically leakage transformers that limit current and prevent overload in neon lighting.
  • PCB Transformers: Transformers that utilize PCBs as a coolant, found in older power transformers, particularly on power poles
  • Safety Site Transformers: Used heavily in construction, these devices step the voltage down to safe levels for use with power tools and other devices
  • Switch Mode Power Supply (SMPS) Transformers: A highly efficient form of transformer used in devices such as personal computers
  • Telecom Transformers: These include signal transformers, a type of pulse transformer, used in the telecom industry.
  • Toroidal Transformers: A ring-shaped transformer design utilized for its compact size and ability to perform with a reduced magnetic field.

What Are Transformer Ferrite Cores?

Some transformers have ferrite cores. These, of course, serve as a means to transfer magnetic flux within the transformer. They are expensive compared to laminated iron cores and are less common.

These devices are common parts of switched-mode power supplies. The ferrite is in powdered form, which allows the transformer to operate at very high frequencies. The devices can also handle a great deal of power without huge increases in size of the device.

What Are Transmission-Line Baluns

Balun is a portmanteau of BALanced and UNbalanced. This refers to the function of these transformers, which is to convert a balanced signal to an unbalanced signal. These devices are very widespread in there usage and you’ll find them in many different applications, including being used on transmission lines.

Transmission line baluns are very simple devices, oftentimes consisting of just a few windings of coaxial cable. They work on a range of materials. They are sometimes utilized without a magnetic material and sometimes with. These devices oftentimes have ferrite cores, but there are among the simplest of all transformers in usage.

What Are Variacs?

The name Variac was first trademarked in 1934— it was held by General Radio—but that trademark expired in 2002. It has since been picked up by Instrument Service Equipment and, currently, the name is among their trademarks. A variance is simply a variable transformer. These are typically autotransformer designs that are utilized to vary output voltage. They operate on a constant AC voltage.

This is a very common type of transformer used in a variety of applications. They are used in everything from advanced testing applications to simple dimmer switches for lighting.

The power of these devices comes from the fact that the number of turns on the coil can be varied, which means that the output voltage can be changed as needed. These devices allow the user to change the output voltage to very precise degrees, making them exceptionally flexible and useful devices.

Variac Brushes

These are among the components in Variacs that define their flexibility. The voltage that these devices put out is determined by the total area of the brush that is in content with the windings. These brushes can be adjusted very precisely, making Variacs excellent for granular control over output voltage.

Variac Connectors

Variacs are used for a wide enough range of applications that there are many different types of connectors available. Some of them include switches that make it easy to externally turn power on or off and others are simpler devices that allow wire to be wrapped round a bold and then fastened into place with a thumb connector.

Variacs are used in hobby applications as variable power supplies, so some connectors are designed for this purpose, as well. There are Variac transformers that come equipped with standard wall socket plugs on them, which are oftentimes used to work with electronics and appliances that cannot function off of standard wall voltage and that need a transformer attached externally to keep the devices safe from overload.

Variac Dials

One of the significant advantages of a Variac is that the brushes tend to have enough resistance to make precise adjustments possible. These adjustments are performed using a dial that gives the output voltage. They vary in size according to the device and allow the user to rotate the knob on the device to higher or lower voltages which, internally, alters the area of the brush making contact with the coils.

Many of these dials are graduated so that the output of the Variac can be customized for the device being powered. For instance, if you had old electronic equipment that required a voltage of 60v and wanted to run it off of 120v wall voltage, you could use the dial on the Variac to adjust the output precisely, verify it with a voltmeter and then plug the device in, giving it the right amount of voltage for the device and protecting it from harm.

Variac Knobs

Most Variacs are adjusted using a simple knob, situated inside the dial. The knob is usually painted with an arrow that lets the user know what the voltage setting is adjusted to at any given time.

Turning the knob requires that the user overcome the resistance of the brushes inside the device, but also makes it easier to make precise adjustments. These knobs, of course, are made of materials that protect the user from shock and make the devices safe to use.

Depending upon the size of the device, the size of the knob can vary considerably. Those Variac devices that are used for hobby and household applications are generally designed so that the knob can be turned easily with the hand. Smaller devices may use less convenient knobs to adjust the voltage, particularly if they are made to be set in place and left once the proper output voltage is achieved.


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