A triac is a device developed back in the USSR at an electrical plant in the city of Saransk. It has 5 pn junctions.
Content
- Operating principle
- Pros and cons of using
- Triac application
The history of its creation falls on the 1960s, at the time when the Mordovian Institute filed a patent for this invention.
Few know how a triac works. Its functioning resembles that of a thyristor.
Operating principle
Perhaps the main difference between a triac and a thyristor is that the first device can pass current in two directions, which is why it found its application in alternating current electrical circuits.
There is no cathode and anode in the triac. This fact is confirmed by studying the current-voltage characteristics of the device.
You can also notice that it has symmetry with the current axis. Its circuit contains two power electrodes (MT1 and MT2) and a control electrode (G). If a voltage with a minus sign is applied to the second indicator, and its indicator turns out to be higher than the set value of the triac operation, and at the same time to supply the power electrode with a voltage sufficient for the flow in the device of a current exceeding the holding current of the triac, then it will pass electricity.
The device will be able to close after the voltage at the power electrode drops to a value at which the device current decreases to the holding current.
The main advantage of the power regulator circuits on the device is the presence of good two-way communication, therefore, there is a unique opportunity to change it directly during the period of work devices.
Such circuits are often used to control light when using well-known incandescent lamps. To implement them, use
-
thyristor; - dinistor;
- triac.
For this mode of operation, 4 methods can be used to supply voltage to MT2 and G (gate electrode). The first two options require a positive voltage to be applied to the power electrode (MT2) and negative or positive voltage to the control electrode. The next two options require a negative voltage to be applied to the power electrode (MT2) and a positive or negative voltage to the control electrode.
It is important that 1-3 methods are considered working, and the fourth is prohibited, since a breakdown can occur in this mode.
Pros and cons of using
In principle, a triac has a number of advantages. Its main advantages are:
- low cost;
- increased service life.
Due to the absence of any mechanical contacts, the device does not spark, which increases the safety of its use, in addition, there is no radio interference during its operation.
The disadvantages of the device usually include its strong overheating in the absence of cooling radiators. Therefore, the device should only be used with light loads on it, or a radiator should be installed.
The device should be fastened to the cooler by fastening using a screw. The device is very sensitive to transients and will not work stably at high frequencies, and also has a strong sensitivity to various kinds of noise and interference.
An example is a computer uninterruptible power supply unit. The essence of its work is that the network current is converted from direct to alternating. When this unit is turned off, the triac begins to take the accumulated electricity from its built-in battery.
Of great importance for a personal computer is played and power supply unit as a whole. With a sharp voltage switching, an unauthorized activation of the triac may occur in the absence of a control voltage. All this can damage him. It is all the fault of the occurrence of interference or voltage surges when working with a load.
To prevent the triac from breaking, you should turn on the RC shunt circuit. However, electrical interference and noise may occur in certain circuits. If they reach the switch-on value, the device will switch on at the wrong time. To avoid this, shorten the wires that lead to the gate or use a shielded cable.
Another way to get rid of noise is to use a 1kΩ resistor.
Triac application
Due to its unique characteristics, simplicity of the device and low cost, the triac is successfully used both in everyday life and in industry, in the following types of equipment:
- ovens;
- ovens;
- lighting regulators;
- drills;
- punchers.
In almost every electrical appliance in the house, there is a triac.
In the industrial field, devices are used to regulate light, in addition, with their help, electrical appliances and electric motors are regulated.
A triac can easily replace electromechanical relays, as it is much more durable and reliable. The device has proven itself very well in the market and, despite the rapidly developing electronics, it is still is in great demand, since it has found wide application not only in home appliances, but also in industry.
