Questions tagged [thyristor]

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Is this thyristor model or circuit wrong?

As far as I understand when the thyristor is triggered it should turn on and remain on unless negative voltage applied to its gate. I found the model from littelfuse website. But I tried the ...
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1answer
28 views

Correct Thyristor IV characteristics

I saw two different IV characteristics of thyristor on the net. First: Second: So far I know, that when the voltage reaches breakdown value, the avalanche breakdown happens in the thyristor ...
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2answers
41 views

What is the meaning of “Sine wave energy per pulse” when referring to thyristors?

I am looking at the datasheet of a Westcode thyristor (specifically, the R3968), and it has the following graph: I am wondering if someone can explain to me what the graph is showing me! I don't ...
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1answer
40 views

For a stack of thyristors, is the “critical rate of rise of off-state voltage” scalable with the number of thyristors?

For example, in a datasheet I am looking at, the critical rate of rise of off-state voltage is given as $$2000V/{\mu s}.$$ If I have, say, five of these thyristors in series, would the total critical ...
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2answers
59 views

What factors affect a thyristor's “circuit commutated turn-off time”?

In datasheets, they give this value at a certain operation point (voltage, current, and di/dt). My question is... What are the effects of changing these parameters. For example, if di/dt is ...
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2answers
64 views

Thyristor not pulling current away

I'm trying to use this thyristor to pull current away from another part of the circuit. I expected that triggering the thyristor would cause current to flow away from the base of transistor T1. ...
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0answers
31 views

Is zero loss turn-off possible for thyristors?

Consider this very basic circuit: simulate this circuit – Schematic created using CircuitLab Don't mind the values - they don't matter, as this question is conceptual. Imagine that Vcomm is ...
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2answers
49 views

Does a thyristor experience loss if it is switched at zero volts?

I have developed a circuit that uses a capacitor's voltage to reverse bias a thyristor. The voltage to reverse bias it is only about 10% of its off-state blocking voltage. I am confused how I ...
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23 views

Maximum current for a turn off thyristor

A gate turn off thyristor \$\beta_{off}=4.1\$ is shorted to a p- layer with doping \$N_A=6.5 \times 10^{13} cm^{-3}\$. If the hole mobility is \$450 cm^{2}/(V.s)\$, and the emitter fingers \$0.34 cm\$...
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0answers
45 views

Voltage and amperage requirements for resistance heating of glass

I am planning to introduce electric heating/boosting in my glass melting furnace. The present temperature of the glass is around 1200 deg C and I need to raise it up to 1300 deg C. I am trying to get ...
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0answers
81 views

Electric heating for glass melting furnace

Some furnaces use electricity for glass melting. Low voltage and high amperage power is passed through the molten glass through 2 molybednum electrodes dipped into the glass. The molten glass acts as ...
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0answers
55 views

Difference of single phase rectifiers

I am trying to understand the difference between the following rectifiers: What would be the difference between these two output voltages? I can see that there would be no negative output voltage in ...
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2answers
148 views

How to separate ground efficiently in a thyristor circuit controlled by sensitive microcontroller

I've been trying to design capacitive discharge ignition circuits using a microcontroller ARM (Texas and ST) without success. Each circuit using them presents intereference problems during spark ...
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1answer
48 views

Why on shutdown the SCR can be compared to a power diode?

I have this as a homework question and can't seem to find the answer in my notes, book or internet. I know they will behave similarly when there is a reverse polarity on both, but the way my professor ...
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3answers
191 views

Xenon Flash thyristor trigger

I'm building a xenon flash unit with a power of 50Ws (300V 1000uF capacitor). I need to trigger it from a microcontroller. For that I use a MOC3041 to opto isolate my µC from the HV circuit and ...
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3answers
133 views

Why are the diodes in this circuit forward biased in spite of no current flowing through them?

Considering the following circuit, Normally in the +ve half cycle SCR1 is triggered after it takes its triggering gate pulse and then D2 becomes intrinsically forward biased so it's on and conducting ...
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1answer
583 views

What distinguishes an ordinary thyristor from a GTO thyristor?

A thyristor, I know, is a four-layer PNPN structure, with an anode on the first P section, a gate on the second P section, and a cathode on the second N section. This simple structure suggests that ...
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3answers
252 views

Testing a thyristor

I have a very large high voltage device that a friend asked me to take a look at. It has a bunch of BIG thyristor packages (Semikron, SKKT 106/18 E, Dual Thyristor Module, 600A 1800V). I'm testing ...
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1answer
102 views

Why the voltage suddenly reduces when thyristors change from forward blocking to conduction mode

As per the diagram: v-I characteristics of SCR is a graph of anode current I A on y-axis & anode to cathode Voltage plotted on x-axis v-I characteristics can be split into two parts namely ...
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7answers
5k views

Relays vs. thyristors: What is best for swiching 230 V lights on and off rapidly (~ 5 Hz)?

I am building my own disco/party lights. 230 V/60 W bulbs, and ideally I would like to switch them on and off at 5 Hz. I was planning on a simple setup with an Arduino controlling the lights. My ...
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1answer
52 views

SCR (thyristor) - Practical Dimmer Circuit

Could someone please explain the main function of the capacitor C3 connected between the gate of the thyristor (through the diac) and the cathode of the thyristor, in this Dimmer circuit schematic
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2answers
137 views

Negative gate SCR

I've accidentally supplied the gate of an high power phase control thyristor (Vdrm=5200V and It(rms)=6500A) with a negative current (about two times the trigger current and four times the trigger ...
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1answer
157 views

Can somebody explain how this circuit works?

I have the following circuit implemented in the control of a thyristor. I know the basic functionality of the circuit, but i need a complete description of every component. Thank you!
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3answers
276 views

Does Thyristor (SCR ) works for Inrush current protection?

Does a SCR ie Thyristor work for Inrush current protection in a circuit ?
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1answer
216 views

Triggering the thyristor for the single phase AC voltage controller in MATLAB

I have been trying to study the output characteristics of a thyristor based single phase AC voltage controller through the model in the picture attached. Could anyone tell me what I could do to ...
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1answer
918 views

Three-phase thyristor rectifier - Minimum firing angle

Why is a minimum firing angle (>0, usually 5-15°) defined for three-phase thyristor rectifier? I would like a technical explanation. Thanks
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1answer
480 views

Parallel RC filter on SCR gate

I came across an old circuit from work that discharges a capacitor (C1) into a step-up transformer to a low-impedance load. This event is triggered by a pulse into an SCR, whom has a parallel RC ...
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2answers
172 views

Why should I specify a 'pulse width' when firing a thyristor rectifier/inverter?

If I'm correct, the controller will send a gate signal to this bridge (6-pulse or 12-pulse) and even if it sends them with 1 degree of width, the thyristors must close until the current through it ...
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1answer
406 views

Thyristor/SCR \$i^2t\$ and \$i^2\sqrt{t}\$ Rating

I have commonly seen the \$i^2t\$ rating for fusing in a SCR datasheet. This is a helpful rating for assessing if pulses which exceed the surge current rating (Itsm) of the SCR will damage it. ...
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2answers
435 views

Thyristor as a traic

I have a thyristor with the connection as in this thyristor (fig 1) and i am trying to use it as a traic. Edit: I am using 3020 optoisolator and resistor value as shown in fig.2 Supply is 220V. Can ...
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1answer
455 views

Capacitor commutation of thyristor and DC load

In my school notes I have been given a basic thyristor circuit. I would like to breadboard a similar circuit and have some questions about choosing a suitable capacitor type and value between points P ...
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1answer
173 views

GTO Driver circuit

i am new to power electronics.I am working in project where input is pulsating dc and i have to control it, i try with scr but we can control only on of scr not off so in some case the cycle cut ...
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2answers
222 views

Inrush current switch with thyristor?

Background: I've a problem where I need to measure the inrush current of some parallel DC/DC converters in a system where the input voltage may vary between 360-600Vdc on start up. The inrush current ...
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2answers
325 views

Replacement Triac

I have a simple dimmer module with a busted Triac MAC97A6. I want to replace that component so that the module will work again but stores near my area don't have that specific component. One store ...
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2answers
3k views

Can a thyristor be built from two transistors?

Supposedly, an SCR/thyristor is just a simple, four layer PNPN semiconductor. If that's the case.. When a circuit calls for a SCR/thyristor, and there isn't one available, can it be substituted by (...
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1answer
92 views

Do phototriac optoisolators (e.g. MOC3021) require pulse trains?

I have a project where I need to make a microcontroller trigger an old, non-controlled, camera flash (think of discharging a capacitor through a xenon lamp). First idea was use a transistor-based ...
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2answers
3k views

Line Commutated Inverter

This is the circuit diagram for a Line Commutated Inverter which I came across in my power electronics book. The input and output voltage waveforms are give below: My logic says that from π to 2π,...
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1answer
703 views

Firing Anti-parallel Thyristors with continuously firing pulse-trains

Can I use two pulse trains as describe below to fire a set of anti-parallel thyristors? Is there any potential danger in this firing scheme? PS: I must use pulse train firing in my application.
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1answer
157 views

Main switch circuit with thyristor and bridge problem

Following circuit is a 220V touch switch from this website: http://8085projects.info/m668-based-touch-sensitive-step-dimmer-circuit.html I'm wondering how it works because the IC take its working ...
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2answers
858 views

IGBT-based capacitor charge transfer and thyristor-based capacitor discharge

simulate this circuit – Schematic created using CircuitLab I am designing a circuit to provide a couple of strong and fast current pulses (~1000 A, more current is better, ~100 us, half-sine) ...
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1answer
198 views

Help with semi-controlled full wave monophasic rectifier using MOC3011 and SCR

I'm trying to build a full wave semi-controlled rectifier with this circuit: The zero's detection is working well and I am firing the TRIAC depending on the position of the potentiometer, the ...
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0answers
849 views

Average output voltage of single-phase thyristor-controlled bridge converter

This question is highly related to this one but I don't find the answers satisfying. I'm a bit confused about the equation for the DC output voltage of phase-controlled bridge rectifiers. \$V_{o_{...
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2answers
516 views

Inner Resistance of TRIAC

Due to some problems in my project, I am curious about the inner resistance of TRIAC when it turns on. I have run some tests. The setup is just like the schematic picture. Rs is the source ...
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1answer
138 views

How to design individual commutation for SCRs in H Bridge configuration?

I am designing a DC drive using SCRs in H bridge(with protection circuits). Triggering is done via an optocoupler. Motor specifics:24V DC , 10 Amps Supply specifics: 24 V DC, 15 Amps(with regulation, ...
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1answer
69 views

Rectifier and thyristor

I'm wondering as to how a system like this: acts, when their thyristors are controlled in various ways. The converters are simple enough, but I'm wondering how the graph made around the voltage ...
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1answer
6k views

Speed control of 3 phase induction motor using thyristor

I am working on project of controlling speed of 3 phase induction motor. To control the speed of motor I am using thyristor TYN16-600CT. As I am searching for ...
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1answer
197 views

Thyristor latching problem

I am attempting to make a circuit which triggers a 555 astable. The input is one of those IR beam break sensors with the output of the phototransistor going to a NOT gate and the output of that is ...
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1answer
2k views

How do I find the firing angle of SCR practically? [closed]

Our teacher told us to find out the time period and then multiply it by 18.Then 180-(∆t*18) gives firing angle.Why 18 as a multiplier?
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1answer
54 views

Thyristor in a choppercircuit

I've the following kown values: Switching on loss is \$\text{E}_\text{on}\space\text{J}\$ in \$t_\text{on}=\tau_\text{on}\space\text{s}\$ Switching off loss is \$\text{E}_\text{off}\space\text{J}\$ ...
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2answers
378 views

Triggering a Thyristor

I am trying to model a thyristor DC switch but I am having problems with properly turning "ON" the SCR that is used as the switch. I am using a 2N1595 SCR and I've looked at its datasheet and it seems ...