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A thyristor is a solid state three terminal electronic power switch with two power terminals which carry the operational part of the device current and one gate or trigger terminal which is used to switch on the thyristor when required.
Whenever the current flowing though it changes diirection or simply falls to zero, a thyristor will switch off.
Unlike a transistor, after its gate/trigger signal is removed a thyristor will remain switched on for as long as the direction of the current flowing through it remains the same, even if the amperage of that current changes.
Unlike a mechanical switch the thyristor has operational supply polarities ( positive & negative of the supply ) which have to be observed. Therefore it can switch on and conduct for one supply polarity only.
Since it is a solid state device a thyristor can operate at much faster switching speeds than any electro-mechanical switch.
With a DC supply of correct polarity, a thyristor will conduct when triggered but will not then switch off till the current is interrupted by some other means such as removal of the supply or by use other, much more complex, circuitry which forces the current to flow in the reverse direction.
With an AC supply, when triggered a thyristor will conduct when the supply is of correct polarity and will then automatically switch off when the AC supply polarity reverses.
For controlled operation in both directions, using the gate as a trigger on the both the forward and the reverse part of the AC Supply, a second thyristor connected with reverse polarity has to be used in parallel with the first one. This idea is basically what is used to make AC lamp dimmers nowadays.
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A thyristor is a transistor having a thyratron-like characteristic; as collector current is increased to a critical value, the alpha (amplification factor) of the unit rises above unity to give a high-speed triggering action.
That description just given (now shown in italics) is wrong! It is not for a thyristor but for a thermistor!
A thermistor is a device with 2 wires coming out of it which changes its resistance to electrical current flow as its temperature is changed. They are used in devices that have to perform some job based on the temperature of the medium they are in.
The thyristor is a solid-state semiconductor device with four layers of alternating N- and P-type material. They act as bi-stable switches, conducting when their gate receives a current pulse, and continue to conduct for as long as they are forward biased. (That is, for as long as the voltage across the device has not reversed).
Some sources define silicon controlled rectifiers and thyristors as synonymous. Other sources define thyristors as a larger set of devices with at least four layers of alternating N and P-type material.
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Re. the error shown in italics above... The first answer at the top of the page is correct: a thyristor (aka SCR or Silicon Controlled Rectifier) is a four layer solid-state switch, and a thermistor is a temperature-sensitive device consisting of a material with a high thermal coefficient of resistance, either positive or negative.
Thyristors are solid-state semiconductor devices with four layers of alternating N- and P-type material. They act as bi-stable switches, conducting when their gate receives a current pulse, and continue to conduct for as long as they are forward-biased (That is, as long as the voltage across the device has not reversed).
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∙ 10y ago
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∙ 13y agonothing
sorry dude how can this be the answer.But the ans is "When the semiconductor device have working similar to that of thyratron tube then it is said to be a thyristor.
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What is the thyristor firing circuit?
The thyristor is basically used a switch in an AC circuit to control the amount of power fed to the load. To turn on this switch an "electric" pulse should be applied to the Gate terminal of the Thyristor. A circuit which supplies the "electric" pulse is called the firing circuit.
What is a line commutation?
it is the natural commutation ...by making open circuit or short circuit on the thyristor to make it turn off.
Why would you color code a Thyristor?
The 3 wires on a Thyristor are colour coded in order not to connect the wrong wire to the incorrect part of the circuit. The three wires are called: anode (OV), cathode (output) and gate (input signal). Sorry I don't know the colours but I hope this helps.
How does a thyristor function?
A thyristor is a semiconductor device which acts as a switch.
Can we replace a thyristor by a mosfet?
No because a mosfet does not work the same as a thyristor. In a thyristor the current flows even when the gate pulse is removed, until the current stops. That is not the case for a FET.
What is the thyristor firing circuit?
The thyristor is basically used a switch in an AC circuit to control the amount of power fed to the load. To turn on this switch an "electric" pulse should be applied to the Gate terminal of the Thyristor. A circuit which supplies the "electric" pulse is called the firing circuit.
What does forced commutation mean?
The term "Forced commutation" is used when a thyristor is turned off using external components. If a thyristor is used in a DC circuit, when first turned on, it will stay on until the current goes to zero. To turn off the thyristor it is possible to use a Forced commutation circuit. The circuit creates a reverse voltage over the thyristor (and a small reverse current) for a short time, but long enough to turn off the thyristor. A simple circuit consist of a precharged capacitor and a switch (e.g. another thyristor) parallel to the thyristor. When the switch is closed, the current is supplied by the capacitor for a short while. This cause a reversed voltage over the thyristor, and the thyristor is turned off.
What is a line commutation?
it is the natural commutation ...by making open circuit or short circuit on the thyristor to make it turn off.
What is thyristors?
A thyristor is a part of a alarm circuit you use it so the alarm stays on
What circumstances led to the invention of the transistor in 1947?
before the invention of transistor,thyristor was used instead of transistor but thyristor produces more heat in the circuit and size is more when compared to transistor
Can a thyristor work as a circuit breaker?
A thyristor is primarily a very fast "switch-on" device and is not designed to be used as a "switch-off" device.A circuit breaker is primarily a "switch-off" device which is used to automatically break the flow of current from a source to a load whenever the amount of current exceeds the rated current value of the breaker.So, because a thyristor does not, all by itself, "open" a circuit, a thyristor cannot be used to work as a circuit breaker.NotesCurrent flow through a thyristor can only stop if - external to it - the current flowing through it gets reduced to below its minimum holding current or, of course, to zero, as would happen either:i) if the load was disconnected from it by a separate circuit breaker that is wired into the circuit between the thyristor and the load;orii) if the source was disconnected from it by a separate circuit breaker that is wired into the circuit between the supply and the thyristor.Further notesA thyristor is designed to close or "make" a circuit whenever:a) an appropriate value of trigger voltage is put onto its gateand then only if:b) the current from the source to the load can flow through it in its "forward" direction.One way of ensuring it automatically disconnects the load from the source is to use an alternating current supply and always "trigger" the thyristor so that it turns on during each positive-going part of each ac cycle.Then, whenever the ac supply voltage returns to zero at the end of each positive half-cycle (after which it goes into the negative half-cycle) the thyristor will automatically break any further flow of current.By using other electronic circuitry to determine exactly when the gate is triggered (earlier or later in each positive-going part of each cycle) the amount of power supplied to the load can be controlled very accurately.That is why the main application for thyristors is to provide a precisely controlled way too use alternating currents to allow varying amounts of power to be supplied to electrical loads.
How does the turn off circuit on a Class B type thyristor work?
The Class B type of commutation circuit uses an LC circuit in parallel with the thyristor. During initial power up, the capacitor C charges to the supply voltage (Edc) and the thyristor is OFF. The initial charging current of the LC branch flows thru the load. When the thyristor is fired, the supply DC voltage is applied across the load, and the voltage across the LC branch goes to almost zero (the forward drop of the thyristor). Then the LC circuit enters a resonant discharge with an angular frequency of the square root of the inverse of LC product. The LC resonant cycle supplies a peak forward current thru the thyristor of Edc times the square root of C/L. This peak current must exceed the load current in order to effect the turn-off of the thyristor during the second half of the discharge resonant cycle. This peak current is usually designed to be twice the load current. The thyristor is reversed biased (and turned OFF) during the first quarter cycle of this second half of the resonant cycle - thus allowing the supply to recharge the capacitor in the LC parallel branch. Then the cycle can repeat.
What does a thyristor works as a circuit breaker?
A thyristor is a type of semi-conductor and is used in a circuit to control the application of electrical power to a load. They are often found as the switching element in light dimmers and can be used as control elements in power supplies (variable or regulated). Types of thyristors are diacs, triacs, sidacs and SCRs (silicon controlled rectifier).
What are types of thyristor?
Types of thyristor firing art
How does the transistor circuit differ from the thyristor circuit?
A thyristor is a "triggered" device. It will remain off until its gate electrode is made to conduct. It will then stay on (showing a very low resistance) until the power is removed, or (in Gate Turn Off devices) until a turnoff voltage is applied. A transistor can be used as a variable-resitance element. While it can be made to switch (like a thyristor) it does not need any special turn-off: just remove the input signal and it will go open circuit. A transistor can be made to respond to a vaying input signal with a varying resistance, so it can be used as a linear (analogue) amplifier.
What does the term 'triac' means?
A "triac" is a type of thyristor designed for electronic control of the current supplied to a circuit, used especially in dimmers for lighting systems.
What is conduction angle in thyristor?
not a clue a A: It all depends on the thyristor. There are no calculation involved not until you look up the thyristor specifications and decide on the load of the thyristor then you may calculate or more likely choose.
