Transformers how does it work

Core losses are from hysteresis and eddy currents. Hysteresis is due to the required power to reverse the magnetic field as it changes direction. This is given off as heat which will then be dissipated from the machine. Eddy currents, on the other hand, are produced by the magnetic field from the primary winding within the core and is not part of the current generated for useful work.

As described above, eddy currents are minimized by using laminations. Copper loss is due to the resistance of the copper windings. All conductors have electrical resistances which cause a voltage drop as an electrical current passes through it. This loss cannot be easily reduced since it requires increasing the cross-section of the conductor.

Consequently, this will require a larger and more expensive transformer. This loss causes a release of energy from the windings in the form of heat. Stray loss is from the leakage of the magnetic field that influences other conductive parts of the transformer. Since this magnetic field is weak compared to what is present in the iron core, the eddy currents produced cause negligible effect. Transformer dielectric materials are the turn-to-turn or layer-to-layer insulation of the windings.

The transformer oil, on the other hand, is used to insulate, prevent arcing, and dissipate heat. Dielectric loss is caused by the degradation of the insulating materials and the transformer oil. Three-phase transformers are transformers that operate with a three-phase electrical system. The type of transformer described in the previous chapter is a simple single-phase transformer. Single-phase and three-phase transformers differ in wiring configurations.

To further understand, it is better to take a look at three-phase electrical systems. Single-phase and three-phase electrical systems use alternating current AC. AC is a form of electricity that is constantly changing amplitude and direction, usually characterized by a sine wave. Though other waveforms can be created such as complex, triangular, and square waves. AC signals have three main properties: period, frequency, and amplitude. Period and frequency describe the time component of the wave, while the amplitude describes the strength or magnitude of the electricity.

One complete AC waveform has a peak and a trough. A single-phase electrical system has a current with one peak and one through flowing on a single conductor. At these points, the amplitude is greatest but in different directions.

For three-phase systems, the current has three peaks and three troughs flowing on three separate conductors. In three-phase electrical systems, it can be observed that the greatest amplitude is reached more frequently for a given period. This helps deliver power at an almost constant rate. A three-phase transformer consists of six windings, three for the primary and three for the secondary. The windings on each side primary and secondary side can be connected in either delta or star configurations.

These windings can be viewed as separate single-phase windings. In theory, three single-phase transformers can be connected creating a three-phase transformer. The two main forms of three-phase connections are delta and star.

The delta connection, also known as mesh connection, consists of three windings connected at the ends of each other forming a closed loop. These ends are connected to a terminal. It can be observed that there is no neutral point. Grounding connections are used instead.

Delta connections can also be configured as high-leg systems by grounding the center point of one phase. In this configuration, the voltage measured across the line opposite to the center-tapped phase and ground is higher than measured across terminals.

The star connection, also known as the wye connection, consists of three windings and four terminals. One end of the three windings is connected to a common neutral point or terminal, while the others form the three phases of the circuit. Using either delta or star connections has its advantages and disadvantages. To further understand, it is best to know the difference between phase and line voltages and current. Phase voltage and current are measured across a single component.

The line voltage and current, on the other hand, are measured across two terminals. Phase and line relationships of delta and star connections are summarized below. Learn how transformers work, how to create a magnetic field with electricity, why only an alternating current can be used in transformers, how a basic transformer works, step up and step down transformers and finally three phase transformers.

Scroll to the bottom to watch the YouTube tutorial. Remember Electricity is dangerous and can be fatal, you should be qualified and competent to carry out any electrical work. Do check those out HERE. When we connect an AC generator to a closed loop of cable, a current will be able to flow through this cable and the direction of the current will alternate backwards and forwards with the rotation of the generator.

You can think of this as the tide of the sea; as it changes direction and reaches its maximum and minimum point. As the current flows through the cable, it will admit a magnetic field. If we passed DC current through the cable, the magnetic field will remain constant, but if we pass AC current through the cable, then the magnetic field will increase and decrease in strength and changes polarity as the current changes direction. If we placed multiple cables together and pass current through them, then the magnetic fields will combine to create a stronger magnetic field.

If we then wrap the cable into a coil, the magnetic field will become even stronger. If we place a second coil in close proximity to the first coil and then pass AC alternating current through the first coil, then the magnetic field it creates will induce a current into the second coil and this magnetic force will push and pull on the free electrons forcing them to move.

The key component here is that the magnetic field is changing polarity as well as intensity. This change in intensity and direction of the magnetic field constantly disturbs the free electrons in a secondary coil and this forces them to move.

This movement is known as electromotive force or EMF. The only time it will cause EMF is very briefly when the primary circuit is opened and closed or when the voltage is increased or decreased. Therefore, we use alternating current as this change occurs constantly.

Now this loop guides the magnetic field along a path to the secondary coil so that they will share the magnetic field and this makes the transformer much more efficient. Now the use of an iron core is not a perfect solution. Some energy will be lost with something known as Eddy Currents where the current swirls around the core and this heats up the transformer which means that the energy is lost as heat.

To reduce this, engineers use laminated sheets of iron to form the core and this greatly reduces the Eddy Currents. Transformers are manufactured to be step up or step down transformers and these are used to increase or decrease the voltage simply by using a different number of turns within the coil on the secondary side. To increase the voltage in a step up transformer; we just need to add more turns to the coil on the secondary side than the primary side.

As expected, the current output is significantly less than the input. In certain spectacular demonstrations, very large voltages are used to produce long arcs, but they are relatively safe because the transformer output does not supply a large current. If there is no change in primary voltage, there is no voltage induced in the secondary. One possibility is to connect DC to the primary coil through a switch.

As the switch is opened and closed, the secondary produces a voltage like that in Figure 4. This is not really a practical alternative, and AC is in common use wherever it is necessary to increase or decrease voltages.

Figure 4. Transformers do not work for pure DC voltage input, but if it is switched on and off as on the top graph, the output will look something like that on the bottom graph. This is not the sinusoidal AC most AC appliances need.

A battery charger meant for a series connection of ten nickel-cadmium batteries total emf of It uses a step-down transformer with a loop primary and a V input. You would expect the secondary to have a small number of loops. The number of loops in the secondary is small, as expected for a step-down transformer.

We also see that a small input current produces a larger output current in a step-down transformer. When transformers are used to operate large magnets, they sometimes have a small number of very heavy loops in the secondary.

This allows the secondary to have low internal resistance and produce large currents. In this case the primary and secondary power is W.

Verify this for yourself as a consistency check. So the AC output of the secondary coil needs to be converted into DC.

This is done using something called a rectifier, which uses devices called diodes that allow only a one-way flow of current. Transformers have many applications in electrical safety systems, which are discussed in Electrical Safety: Systems and Devices. A step-up transformer increases voltage and decreases current, whereas a step-down transformer decreases voltage and increases current.

Conceptual Questions 1. A step-up transformer with 1, turns on the primary fed by V a. The iron core is itself a crude secondary like a coil of one turn and changes of primary current induce little circular voltages in the core. Iron is a conductor and if the iron core were solid, the induced voltages would drive wasteful secondary currents in it called eddy currents.

So the core is made of very thin sheets clamped together, with the face of each sheet coated to make it a poor conductor. The edges of the sheets can be seen by looking at the edges of a transformer core.

For 9 Resources. The following guidance notes cover these practical collections: Permanent magnets For 4 Resources. We have all seen this slogan, but does it make a difference?