If you’ve been around electric appliances for any amount of time, you’d probably have heard of the transformer. Yes, they are those huge bulky things found in street corners, which make random scary noises and occasionally spit sparks. Your phone charger also has a kind of small transformer too, but much, much smaller and with a completely different mechanism.

What is a Transformer?

一个transformeris a device that uses the principles of electromagnetism to convert one voltage or current to another. It consists of a pair of insulated wires wound around a magnetic core. The winding to which we connect the voltage or current to be converted is called the primary winding and the output winding is called the secondary winding.

变压器有两种品种,加大范围h increases the voltage or current, and steps down, which decreases the voltage or current input. For example, the transformer in your microwave Oven is a secondary transformer that is used to supply around 2200Volts to the vacuum tube in the Microwave Oven.

要注意的一件事是，变形金刚仅处理更换或交流电压，并且不与DC一起使用。我们现在将了解原因。

How important are transformers in the electrical system?

It was around 1856 when two brilliant minds Nikola Tesla and Thomas Edison were having a rivalry against each other. Those were the times when electricity and its applications of glowing a bulb and running a motor were just being noticed. It was Edison and his associates who first discovered DC (Direct Current) system, then sometime after that Tesla came up with his AC (Alternating current) system. Since then, both were trying to prove that their system is more advantageous than the other.

By then, the time has come for houses to get electricity. While Edison was busy demonstrating how dangerous AC is by electrocuting elephants, Tesla and his team came up with the transformers which made transmitting electricity a lot easier and more efficient. Even, today Transformers play a vital role in the transmission system. Let’s know why.

与高电压和lo传输电力w currents will help us reduce the thickness of the transmission wires and thus the cost, it also increases the efficiency of the system. For this reason, a standard transmission system can be anywhere between 22KV to 66KV, while some generators in the power plant has an output voltage of only 11kV, and the household AC appliance requires only 220V/110V. So where does this voltage conversion take place and who does it.

问题的答案是变形金刚。从电厂到您的房屋，系统中将有变压器会加强（增加电压）或降低电压（降压电压），以保持系统的效率。这就是为什么变压器称为电气传输系统的心脏的原因。我们将在本文中了解更多有关它们的信息。

Transformer Symbols

The circuit symbol for a transformer is simply two电感器并排组合相同的核心。两个绕组之间的线的性质表示所使用的核心类型：虚线表示铁氧体，两条平行线表示层压铁，无线表示空气芯。

有时，“颠簸”的数量被用作变压器函数的粗略指示 - 一侧的颠簸更少，另一侧的颠簸可能意味着第一侧的弯曲数比另一侧少。

变压器如何工作？

至understand the working of a transformer, we need to go back in time, to Michael Faraday’s laboratory.

Michael Faraday can perhaps be called the father of the transformer since it was his experiments that helped us understand electromagnetism and develop devices like motors and generators.

In the late 1800s, when it was discovered that electricity and magnetism were related phenomena, there was a race to try and build a practical device that could harness the power of magnets to generate electricity.

Faraday found out that electricity could be generated by bringing a magnet close to a coil of wire. What he discovered was that voltage will be produced only when the magnetic field was changing, that is, if he moved either the coil or the magnet relative to the other.

In DC, the current flow is steady and so is the magnetic field. Since the field is steady and not changing, there is no voltage induced on the secondary and the transformer just looks like a normal coil of resistive wire to the power supply. So transformers do not work with DC currents.

他还发现，当两个线圈保持彼此靠近时，一个线圈中流动的电流可能会诱导另一个线圈中的电流。该原则称为相互感应，并控制所有现代变压器的工作。

一个s shown in the figure, the transformer consists of two windings wound on a magnetic core.

The purpose of having a core is because air is not a very good supporter of magnetic fields, so having a magnetic core increases the magnetic field for a given amount of current flowing through one winding, which in turn creates a stronger current in the other, increasing the overall efficiency of the device.

When a current passes through the primary, a magnetic field is set up in the core and is confined mostly to the core.

该磁场通过次级的中间，因此通过相互诱导定律诱导另一个电流。

该系统的优点在于，输入电压与输出电压的比率仅仅是主要绕组和次级绕组的比率，该公式总结为：

Vout/Vin = Nsec/Npri

如果VOUT是输出电压，则VIN是输入电压，NSEC是次级绕组中的转弯次数，而NPRI是主绕组中的转弯数。

So if you have two transformers, one with 100 turns on the primary and 1000 on the secondary and another with 10 turns on the primary and 100 turns on the secondary, you can calculate the turns ratio to be 1:10 for both, so they both step up voltage to the same level.

Transformer Properties

If we have a closer look at the example given above, the first transformer will have a greater winding resistance (since more wire is used) and in some cases that might limit the amount of current that can be drawn from the transformer. This property is called winding resistance, but in most cases it does not really matter since the copper wire used generally has a low resistance.

您注意到的另一件事是，初级和次要绕组之间没有直接的电气连接。这称为电流隔离，正如我们将看到的那样，可以非常有用。

Looking at each of the transformer windings, we can see that they are constructed just like inductors – a coil of wire wound around a magnetic core – and have an inductance too.

这种电感与该公式给出的转弯数的平方成正比：

lpri/lsec = npri2/nsec2

如果LPRI是初级绕组的电感，则LSEC是次级绕组的电感，NPRI是初级旋转的数量，而NSEC的转弯数是次级绕组的转弯数。

The proportionality constant for a given core can be found in the datasheet and is usually given in units of µH/turn2. The exact value depends on the type and size of core.

Supposing you have a transformer core with a specification of 1uH/turn2. If you wind one winding on that core, then the inductance will be the value of the constant multiplied by the number of turns squared, in this case 1. So the inductance of that one winding will be 1µH. If you wind another winding with 10 turns on the same core, then the inductance will be:

（1µh/turn2）*（10圈）2 = 100µH

Since the windings have inductance, they provide an impedance to AC signals, given by the formula:

XL = 2π*f*L

其中XL是欧姆的阻抗，F是欧姆的频率，L是Henries中的电感。

Say you want to design a transformer that draws 3A at 220V AC at 50Hz, which is standard power line frequency. Then the impedance of the primary would need to be 73.3 Ohms by Ohm’s law. Now that we know the impedance required and the frequency, we can rearrange the formula to find out the inductance necessary for the winding:

L = (XL)/(2π*f)

Substituting the values, we find that the inductance needed would be 233mH.

Using this information and the value of µH/turns2 from the datasheet, we can calculate the windings required to get the inductance required.

Supposing that value is 50µH/turns2, then we can rearrange the formula to find out the inductance:

其中n是转弯次数，l是所需的电感，而t2/µh项仅仅是数据表值的倒数。

一个pplying our values in the formula, we get a required number of turns of 2158. So as you can see, one you get the hang of the formulas, you can design transformers for nearly any application!

变压器构造

对于需要缠绕自己的变压器的任何人，transformer constructionis essential.

一个transformer consists of a few basic components, below are the transformer parts:

1.梭芯：

The bobbin is the basic framework for any transformers. It provides a spool on which to wind the windings and also holds the core in place. It is usually made up of a heat resistant plastic. It also sometimes contains metal pins onto which you can solder the ends of the windings if you want to mount it to a PCB, for instance.

2.核心

This is probably the most important part of the transformer. As shown in the picture, the cores can come in many shapes and sizes. It is the magnetic properties of the core that determine the electrical properties of the transformer which is built around the core.

3. WINDINGS

Thought it may seem like a trivial thing, the wire used in the construction is as important as any other aspect. Solid enameled copper wire is generally used, since the insulation is strong and thin, so no wasted space due to plastic insulating sheaths.

变压器的应用

1. MAINS VOLTAGE CONVERSION

This is probably the most common application for transformers – stepping down mains voltage for low voltage appliances. You might even find these inside things like microwaves and old TVs and wall brick power supplies. These transformers have iron cores which gives excellent permeability but makes them bulky and somewhat less powerful than other types.

They are marked like 12-0-12 or 6-0-6 with three secondary wires. This means that the outer two wires have an output of 12V AC RMS if you make the center wire the ground reference. If you measure across both the 12v winding, you will get 24V AC RMS. This gives you flexibility on how you might want to use the transformer.

2.开关模式电源

These are a very special type of power supplies that take a DC input and produce a DC output. They are found all modern phone chargers. The transformers used in these PSUs are designed more like inductors with a small number of turns and ferrite cores with medium-to-high permeability. A DC voltage is applied across the ‘primary’ for a short time so that the current ramps up to a certain level and stores some magnetic energy in the core. This energy is then transferred to the secondary at a lower voltage because it has a smaller number of turns. They operate at high frequencies and achieve excellent efficiencies and are very small.

3. ELECTRICAL ISOLATION

这些是特殊的变压器，比率为1：1，因此输入和输出电压相同。它们被用来使电器从电源地球解脱出来。由于电源是地球引用的，因此即使触摸一根电线也会导致冲击，因为返回路径实际上是地面。由于变压器是循环分离的，因此使用隔离变压器“断开”设备从电源地球上进行了。

4. VOLTAGE CONVERSION TRANSFORMERS

世界各地的大多数国家都使用220V AC作为标准供应电压，但像美国这样的一些国家使用110V AC。这意味着在所有国家 /地区都不能使用一些搅拌机等设备。为此，我们可以使用将110V转换为220V的变压器，反之亦然，以确保可以在任何国家 /地区使用电器。

5.阻抗匹配

These are special kinds of transformers that are used to match the impedance of the source and the load. They see extensive use in RF and audio circuits.

转弯比等于源和载荷阻抗的平方根。

6.自动转换器

这是一种特殊的变压器类型，只有一个绕组，带有构成次要的“ TAP”输出。通常，此水龙头是可变的，因此您可以更改输出交流电压，有点像电压分隔器。

Conclusion

变压器是有用的设备，学习如何设计和使用它们可能会非常方便！虽然我们在这里介绍了基础知识，但从头开始设计一个变压器是可以在另一篇文章中讨论的事情，因此让我们在其他时间内进行了一些讨论。因此，现在，当您再次看到变压器时，您将知道为什么它在那里以及如何工作。