Application of UJT

UJT stand for unijunction transistor, it is most commonly used in high switching speed, Here this article gives the information about the application of UJT to better understand this topic.

Application of UJT:

• The most application of the UJT  transistor is as a triggering device for SCR and TRIACS.
• UJT applications include simple oscillators, phase control.
• The simplest of all UJT circuits is the relaxation oscillator and it producing non-sinusoidal waveforms.
• It is used as a voltage detector.
• UJT is mainly used in phase control and timing circuits.
• It is used in saw tooth generators.
• It is used in oscillator circuit design.
• UJT can also be used as to measure the magnetic flux.

Advantages and disadvantages of thyristors

The terms thyristor denotes a family of semiconductor devices and it is used for power control in DC and AC system. One of the oldest methods of this thyristor family called silicon control rectifier (SCR). This article gives information about some advantages and disadvantages of the thyristor to know more details about thyristor.

Advantages of Thyristor :

• It is easy to turn on
• It is able to control AC power
• It can switch high voltage, a high current device
• It cost is very low
• It is simple to control
• It can be protected with the help of use
• It can handle large voltage, power as well as current
• It is a much smaller in size compared to the transformer 
• The triggering circuit for SCR is simple

Disadvantages of Thyristor :

• It can not be negative
• It can not be used higher frequency
• It can not be  easily turn off
• In the AC circuit, it need to be turn on each cycle
• Gate current can not be negative
• Low switching speed

Explore more information:

1. Advantages and disadvantage of BJT

Thyristor Triac

SCR stands for Silicon Control Rectifier is a unidirectional device that can conduct from anode to cathode only and not from cathode to anode while A Triac can conduct in both the directions. 

A TRIAC is thus bidirectional thyristor with three terminals device. Thyristor used extensively used for the control of power in the AC circuit. 

Circuit Symbol 

The word of Triac stands for is comings from by combining the capital letters from the word TRIode and AC. When in operation, a Triac is equivalent to two SCRs connected in anti-parallel to shown in a figure. The circuit symbol and its characteristics are shown in the figure given below.

Characteristics of TRIAC

This article also gives some advantages and disadvantages of TRIAC to know more learn about TRIAC device in power electronics engineering. 

Advantages of  TRIAC :

• It needs a single fuse for protection
• It can be triggered with positive or negative polarities of glass pulses
• When the voltage reduced to zero the TRIAC turns off
• It needs a single heat sink of slightly larger size compared to other

Disadvantages of TRIAC :

• It is not suitable for DC application
• It has a very high switching delay
• It can be triggered in any direction 
• It is not much reliable than SCR
• It has a low rating compared to SCR
• dv/dt rating is very low than SCR

Thyristor based project

One of the best advantages of thyristor has over other switching devices, a thyristor, for instance, an instance for a thyristor is that signaling of current does not need to be maintained for the thyristor (SCR) device to remain in its conducting state. The thyristor can be used much more application in daily life. Here this article gives information about the thyristor-based project to know more learn about thyristor.

• Thyristor based dual converter
• Thyristor based sensor alarm system
• Thyristor based cyclo-converter
• Thyristor power control by IR remote
• Heat control circuit using SCR
• Flexible AC transmission by thyristor switch reactance
• Emergency light system control using SCR
• Thyristor based speed control of DC motor
• Automatic street light circuit 200 A.C with SCR
• Overvoltage protection using SCR
• Thyristor control power for induction motor
• SCR robot
• Thyristor trigger using a microcontroller
• Thyristor based interfacing
• Ac switching using triac
• Intruder alarms using SCR
• Battery charging by thyristor triggering control
• Thyristor power control using a TV remote

Thyristor Basics

Thyristor or a silicon control rectifier (SCR full form) is basically four semiconductor rectifier, it consists of alternating n and p types of materials forming three P-N junctions which can be a switch from off - state to on-state. It is a similar construction of transistor.

One of the best advantages of thyristor has over other switching devices, a thyristor, for instance, an instance for a thyristor is that signaling of current does not need to be maintained for the thyristor device to remain in it's on conducting state. The silicon controlled rectifier(SCR) is the most popular member of the thyristor family.

There are several other members of thyristor family like PUT, SCS, SUC, TRIAC, DIAC etc.

Thyristor basic three modes of operation :

• Reverse blocking operation
• Forward blocking mode
• Forward conducting mode