Questions tagged [thyristor]

A three-terminal semiconductor device consisting of four layers of alternating type (N or P). The main terminals are the anode and cathode, connected to opposite ends of the four layers. The third terminal is called the gate, and a current trigger at the gate causes the device to conduct if it is forward biased.

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How to make a MHz-fast, 5 volt thyristor with discrete components? [closed]

Off-the-shelf thyristors are optimized to switch at mains frequency, - 60 Hz in the U.S.A. In my application, I need MHz speeds, 10 to 20 watts, 5 to 10 volts. Is it possible to emulate thyristor ...
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How do I calculate the potentiometer value for the controlling of Alpha angle of a phase control IC? [closed]

The datasheet suggests to use a 10Kohm pot to control the Alpha angle, however no matter how much I try I can't control it. I used 1Mohm pot instead and now I can control it more, but still with very ...
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Is this output signal good to drive a thyristor gate?

I have the following signals: Blue is the input to the 10ohm resistor connected to the gate of the 2N7000 transistor Yellow is the output of the pulse transformer GG3 and K3 Is the output of the pulse ...
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simulation (in Falstad's app) of thyristor using transistors fails

I am trying to simulate thyristor behavior with transistors PNP and NPN but it fails (is it a bug of app?). When lower switch is open(and was never closed) and upper closed then current flows through &...
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SCR inverter (thyristor H-Bridge) schematics/working principle?

Several online articles mention the so-called "Single phase SCR Inverter". Sample schematic is attached below. In reality, this, of course, will not work, since SCR2 when activated after ...
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Thyristor Power Loss

i want to calculate the power loss of a thyristor with datasheet's parameters and i found this formula from here Application Note: Conduction loss: Total loss: How can i calculate the power loss if ...
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Thyristor controlled 3-phase heater control, spiky current

Lets say you have 10 thyristor controlled heaters in a 3-phase system. The control of these thyristors is sync'd, so the current draw is spiky (all of the heaters draw current from the same phase when ...
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Gate Drive Circuit of an AC Voltage Controller

The circuit shown is used to control the gate drive of an AC Voltage Controller. I am trying to understand the functions of each of the parts and cannot understand the need of the NPN transistors Q1 ...
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What is the role of D2 and D3 in this circuit?

Explanation of the circuit : This is a simple battery charger based on SCR is shown here. Here the SCR rectifies the AC mains voltage to charge the battery. When the battery connected to the charger ...
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Why does the output voltage of this single phase semi converter ignores the voltage provided by the second thyristor?

Here is the circuit: The first and second circuits are equivalent except that the first one has a capacitor in parallel with the load, i'm trying to smooth out the output voltage. The triggering ...
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Why does this circuit with thyristors change the period of its pulses provided when I have capacitors?

Here's the circuit and its output, everything good so far: When I add a capacitor this happens: For some reason the capacitor seems to be messing up the pulse generator used for the thyristor ...
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Why is there a minimum current in a class-a chopper?

$$i_o(t) = {{{V - E} \over {R}} \cdot (1-e^{-{R \over L}\cdot t}) + I_{min} \cdot {e^{-{R \over L}\cdot t}}}$$ Where is the minimum current from, and why are we dividing by R? This is the link https:/...
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Why does this circuit with thyristors ignore the pulse provided at the gate terminal

Here's the circuit: T1 and T2 are two thyristors where i provide pulse at their gates. Here's the output: For some reason Vout follow Vin before the pulse at T1 happens when Vout before the pulse ...
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1 answer
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Can I put high voltage thyristors in series & ZVS to handle MHz frequency resonance?

I'm trying to scale up a circuit that calls for a MOSFET and a ZVS to be capable of dealing with high frequencies (1-20 MHz.) I'm aiming to crank it up to 10 kV and would prefer the systems in series ...
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Use SCR and resistor as an inrush current limiter

I try to design an inrush current limiter using an SCR S2800F (https://datasheetspdf.com/pdf-file/1129612/Motorola/S2800F/1) and a resistor, as shown in the below diagram. A 600 VDC power supply ...
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2 answers
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Why do we use thyristors instead of regular diodes for high voltage direct current?

Usually, power lines over large distances use alternating current (AC). However, in some cases, direct current (DC) is also used, as high voltage direct current (HVDC), where the high voltage is used ...
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1 answer
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How to calculate current RMS value for full-wave controlled rectifier in degrees?

I'm trying to find the clear way to calculate the current RMS value for full-wave controlled rectifier. Should I include the pi value if the calculation is in degrees since the trigger angle is in ...
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Thyristor latching current and holding resistance

Is there a formula for calculating the latching current of a thyristor and the resistance of the thyristor after it forward conducts and I_gate becomes 0? I couldn't find anything online; the ...
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5 votes
1 answer
747 views

What is the reason of difference in distributed gate thyristor design

As in the pictures, they use different designs (current rate, voltage rate etc. are same.) What is difference between these two designs?
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Diagnosing dead soldering-iron

My soldering iron was working fine for a few years. One day, I used it and it worked fine again, then I unplugged it then tried to use it again a couple of hours later but it wouldn't heat up. I took ...
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How to set the appropriate values to my overvoltage detector using UJT in Multisim?

Overvoltage detector using UJT in Multisim: Online class isn't really helping. I've tried experimenting with values of the components to see if this device is working. I copied its circuit diagram ...
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1 answer
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Rectified signal from three phase rectifier circuit

I'm trying to simulate this circuit This is the implementation I'm getting this output signal, that is close to what you would expect from a rectifier. In this image α = 0, α1 = π/6, α2 = 5π/6 and ...
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Three phase rectifier with thyristors not working as expected

I'm trying to simulate the following circuit with a resistive load: The control circuit provides three signals, and are the turn on signals for the thyristors: the first one (yellow) α1 = α + π/6: ...
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Change DC motor direction with rectified voltage

I'm working with the following circuit: It has a DC motor. The VDC can be changed by controlling the thyristor turn on angle. I would like to add a switch to also change the DC motor direction, but I'...
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RL circuit with thyristor not working as expected

I'm trying to simulate the following circuit to test how it works: The control circuit uses a PIC 18F4550. The isolation circuit, and main circuit are these: Unfortunately when I try to simulate ...
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PSIM: thyristor acting as a diode in a full bridge rectifier with C filter

We were asked to simulate a controlled bridge rectifier with C filter for class. Whatever I change the firing angle into, the output stays the same (Same Vdc). I thought that a capacitor filter couldn'...
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1 answer
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Thyristor controlled regulator

Why when I apply a firing angle alfa with a thyristor controlled regulator the current is zero in the red line drawn in the figure? I think that the thyristor opens the circuit, but why it does so? ...
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2 answers
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What does 'not controllable' mean in power electronics?

A book says that the power diode is 'not controllable' whereas a 'Thyristor' is semi-controlled and a 'MOSFET' is fully controlled. What do these degrees of controllability mean? Is it somehow related ...
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-1 votes
1 answer
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Why do we need 2 different grounds for connecting 2 thyristors back to back?

As seen above, these thyristors are connected back to back to resemble a TRIAC, but for high power applications. People say because they get shorted, but how exactly? Thank you.
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If you have a MOSFET in series with a thyristor, can turning the MOSFET off cause the thyristor to turn off?

This is a purely theoretical question. The values in the circuit below do not matter, and I understand the circuit is completely useless. Consider if SCR1 and M1 are both turned on so that current is ...
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1 answer
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control ac motor with SCR

I want to repair the circuit of a Mixer that used the TS820 thyristor. The other components were healthy except the thyristor so I replaced the TS820 with the BT151 but the circuit did not work. Now I ...
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common circuit to turn on/off ac motor of 110V AC or 230V AC using MOC3041 and BTA16 Resistor calculation

I am building a common circuit to turn on/off ac motor of 110V AC or 230V AC using MOC3041 and BTA16. How do i calculate both resistor value R and Rg ( With Wattage ). For accurate control of TRIC. ...
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1 vote
1 answer
57 views

Common Ground across SCR and Diode Bridge

I am trying to use a common ground to enable a regulated output across the circuit, however as you can see the SCRs and Bridge use the common earth to relay the positive channel in the bus.. Is this ...
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4 answers
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How does a capacitor and resistor affect an SCR's firing angle?

Greetings! High schooler here studying SCRs. I've been looking at sites and books on the concept of increasing an SCR's firing angle, and what I've noticed with these references is that they show you ...
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1 vote
1 answer
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A question on thyristors and phase control

High schooler here reading on thyristors. Videos online and books say they can be used as light dimmers. I assume that's because we can control the amount of current that can enter a load. But what ...
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-1 votes
1 answer
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6 thyristor scr

I have three thyristor and three diodes scr working inside welding machine and drived by good pcb (working very good ). The problem is that I need to replace the three diode by thyristor to use all 6 ...
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Single-phase thyristor full bridge rectifier vs three-phase thyristor full bridge rectifier

For Single-phase thyristor full bridge rectifier compared to a three-phase thyristor full bridge rectifier, with regards the input current harmonics, does the three- phase rectifier have an advantage ...
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1 answer
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Thyristor turn off time in circuit with RL load?

For circuits like this where the src is turned on, and should turn off in beta as shown in the second image. What happens when the diode doesnt conduct after pi, when the voltage is negative, will the ...
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Transient voltage supression for high voltage Thyristor or Avalanche TVS

I am making a high voltage 240 VAC 60Hz voltage measurement front end and is in need of a transient suppression device. According the a table in wikipedia. Avalanche and Thyristors are the only ...
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1 vote
1 answer
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Controlling underdamped LC circuit with thyristor

I am trying to design a circuit that gives me an underdamped sine wave. I am controlling the SCR from an external transformer by microcontroller. When I simulate this circuit, V3 has no effect on the ...
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Thyristor leaking AC? Reading thyristor code?

I'm refurbishing an automotive battery charger. It uses a full-wave rectifier in combination with a thyristor (which I think is acting as output cutoff). The charger output has is the correct DC ...
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1 answer
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Switching from full to half wave rectification

The Context: Multiple manufacturers of electro-magnetic brakes offer rectifier modules to switch their DC brakes with an AC feed. This can often be tied to the same phases turning the motor, so that ...
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1 answer
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One button circuit with thyristor, controling power suply

Please forgive my lack of knowlige. I need to make circuit with one button(normaly OFF, ON while pressing) using thyristor. This circuit will be connecting and disconnecting raspberry pi and bunch of ...
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2 votes
0 answers
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Resonant frequency of a three phase thyristor rectifier

I am trying to inspect how my circuit behaves at operating points around resonant frequency. Is resonant frequency simple equal to 1/(2Pisqrt(LC)) = 1/(2pisqrt(590uH240uF)) = 423 Hz (see the circuit ...
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How to increase the peak current to 12 kA in my circuit?

I am simulating a circuit with a capacitor bank. I am getting maximum peak current to 8.8kA. I need to know how can I increase the peak current to 12-15 kA without increasing the input voltage. The ...
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2 votes
1 answer
72 views

Can a thyristor regain its forward/reverse blocking capability if the current through it is "instantly" brought to zero?

I am imagining a situation where we have several series-connected thyristors, say 10, each that can block a voltage of 100V. So, the ten series-connected thyristors together can block a total voltage ...
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2 votes
1 answer
110 views

What type of vintage semiconductor device is this? Is it an SCR?

I found this circuit board from an 1980s old humidity controlled chamber. This definitely looks like a temperature regulator of some sort. It has a M logo which means made by Motorola. It has the ...
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4 votes
2 answers
309 views

Thyristor SCR gate trigger

I'll work for the first time with a Hockey Puck type SCR with a high di/dt application. So far I've mounted it properly, with the proper clamp and heatsinks. Now I'm concerned with the gate drive, ...
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1 answer
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Why are thyristors used in xenon trigger coil circuits?

Looking at the datasheet for the ZS1031-11(H) trigger coil, the test setup activates the trigger coil with a thyristor: In the datasheets for other trigger coils, and in other circuit diagrams online,...
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3 votes
1 answer
278 views

Problem with SCR latching circuit

I put this circuit together to demonstrate latching properties of SCRs but I'm finding that the SCR doesn't behave as I expected it to from the datasheet values. Specifically, I found that in the ...
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