Questions tagged [scr]

A Silicon Controlled Rectifier - A PNPN or NPNP semiconductor device that once triggered stays in permanently conductive state until the current is removed. USed in protective circuits and chopper style light dimmer switches. Also know as a thyristor.

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Formula of snubber capacitor capacitance for SCR dV/dt protection

I have a formula here for finding the suitable value of shunt capacitance to be put on an SCR snubber: $$ C=\frac{1}{2L}\left(\frac{0.546 V}{\frac{dV}{dt}} \right)^2 $$ L is the snubber inductor, V is ...
2 votes
2 answers
232 views

Cheapest solid-state way to turn a 240 VAC, 15 W resistive load on/off

I need to be able to pulse a 240 VAC, 15 W resistive load on and back off. I need it to turn on only for a single line cycle, then it will remain off for at least 60 seconds, so perhaps the components ...
2 votes
2 answers
621 views

How do DIACs work?

I edited my whole post for more refreshed information I learned about DIACs. Let's consider the following circuit and how it works: First of all the Vs must be higher than break voltage of DIAC so ...
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1 answer
77 views

How to determine saturation in DC smoothing choke with capacitor, and how to simulate in LTspice?

This question addresses some of the issues with a choke made from a microwave oven transformer for producing smooth DC from a phase-fired SCR controller, as discussed in this question. The choke ...
5 votes
2 answers
217 views

What is the reason for the "back porch" current requirement on an SCR gate driver?

I am studying SCR gate drivers at the moment and I would like to understand their fundamentals. Looking at a SCR datasheet (for example, this one section 7 or this application note fig 6 p4,) one see ...
6 votes
4 answers
2k views

Should I gate SCRs on when reverse-biased?

I've been told that it's a bad idea to gate SCRs on when reverse-biased. Is that accurate? I'm reasonably confident that the SCRs won't actually conduct reverse-biased whether gated or not; are there ...
0 votes
1 answer
86 views

Is it possible to use an MOV instead of a flyback diode in a pulse circuit?

I am working on a small high-voltage pulse circuit to protect my animals. I have a question about the flyback diode D2 to protect the SCR. The flyback diode seems to waste a lot of energy between ...
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1 answer
2k views

Is it possible to replace a DIAC circuit with an SCR circuit to drive a TRIAC

I have a triac DIAC cirtcuit. I don't have any DIACs on hand, but I do have plenty of TN1215s. Is it possible to generate the required pulses using an SCR to drive the TRIAC's gate?
1 vote
1 answer
1k views

Confused with turn on time definition of an SCR

The following question I encountered is asking about the minimum time for applied voltage to the gate of an SCR to turn it ON: And below is the solution: I can understand the solution looking for ...
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0 answers
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What is minimum holding current in CT based SCR switch?

I am looking to use a CT based SCR switch to switch an AC contactor. The switch specs list the following: Off state voltage: 240 VAC RMS max. Minimum holding current: 10 mA. On state current: 1.0 AAC ...
0 votes
1 answer
92 views

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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1 answer
82 views

Kiln SSR zero-cross frequency

I am planning on using a WATLOW DC2T-24C0-0000 power controller for a three phase electric kiln. It is a zero-cross 3 phase, 2 leg controlled contactor capable of driving 46 amps with its huge heat ...
2 votes
1 answer
203 views

Why aren't smoothing capacitors used in smoothing the output of fully controlled bridge rectifiers?

I was wondering why smoothing capacitors are not used in smoothing the output of fully controlled bridge rectifiers, like it is used in the uncontrolled bridge rectifiers.
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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 ...
1 vote
0 answers
58 views

Recommendation for optocoupler for SCR and TRIAC Gate driver

I want to use an SCR having gate current "Igt" = 50mA and a TRIAC with Igt = 50mA to 100mA. I am looking for an optocoupler IC to drive the SCR and TRIAC. I saw MOC3021 but it's "LED ...
3 votes
1 answer
160 views

Semi-controlled full wave rectifier

First, a little background. I picked up a Canadian-made 1971 Lincoln Idealarc 250 on the cheap with the intention of turning it into a constant voltage capable machine for wire processes. The fan ran ...
-1 votes
1 answer
209 views

How I can calculate the switching frequency of an SCR and replacing diode with SCR in boost converter? [closed]

I want to find the switching frequency of SCR. I want to use an SCR or a GTO thyristor so I can use a switching frequency up to 20 kHz, but as I am new so I am unable to find the SCR frequency from ...
2 votes
1 answer
573 views

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 ...
2 votes
0 answers
66 views

Need help building simple burglar alarm circuit

I'm trying to build a simple burglar alarm circuit and I've found one online that uses a knife switch, 9 V power source and an SCR. I'm trying to change it over to a PIR motion sensor but am unsure ...
0 votes
1 answer
107 views

How to control voltage using PID when driving SCR?

I am designing a scr based digital battery charger for the first time and have successfully driven scr to provide 110V-DC from a 140V singe-phase transformer. 2 SCR-diode combination forms full bridge ...
0 votes
1 answer
118 views

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 ...
2 votes
1 answer
272 views

Turning on SCR without latching it

The picture shows a typical SCR circuit. I have already simulated this circuit in multisim. Since multisim assumes this to be an ideal SCR (zero voltage drop for example,) the characteristics may not ...
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1 answer
333 views

SCR latching current and holding current equivalent definition

understanding the definitions of Latching and holding current. suppose a particular value of the gate current I_g is given. Now that we increase the voltage across the SCR from 0V and onwards. Forward ...
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1 answer
128 views

What circuit is used in industry for SCR firing?

I am a hardware developer. I have a requirement for designing a firing card for SCR. I am not very used to using thyristors and it has been a long time since I used one. I see on the internet there ...
0 votes
1 answer
121 views

SCR bridge control circuit

I want to design a single phase 400V 1A power supply using mains (230VAC,50Hz). For which I plan to use a step up transformer which will step up to 400V and then an SCR Bridge rectifier to convert it ...
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1 answer
219 views

Industrial SCR rectifier/battery charger circuit: best place for blocking diode, reverse diode, and dropper diodes?

I am working on a three phase 110 VDC & 100 A SCR rectifier/battery charger. I'm not sure which one of the circuits in the image is better for filter and diodes. Please help me with these ...
0 votes
2 answers
145 views

SCR crowbar circuit gate voltage?

I'm designing a simple overvoltage / reverse voltage protection circuit for a 24 V battery system, with plans to upgrade to a 48 V lithium setup in the future. I selected the parts to trigger on a ...
0 votes
2 answers
158 views

How to build a DC motor speed controller with DC source and SCR?

So after asking a question from the book "Practical electronics for inventors" and getting recommendations to burn the book, I'm going to start this thread with the premise that I'm not ...
0 votes
2 answers
268 views

Replacing Darlington with MOSFET for capacitive discharge circuit into a solenoid?

I have the following circuit and criteria and am wondering if it makes sense to replace the Darlington transistor with a MOSFET, and if so how would that change the circuit? This circuit turns on T1 ...
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1 answer
124 views

How does this Snap Circuits SCR circuit work?

I came across some custom Snap Circuits projects. One of them was a homemade SCR out of non polarized capacitors, two bipolar (NPN) and (PNP) transistors, some resistors, and an L.E.D. I am very ...
0 votes
1 answer
296 views

What can I use to turn on a circuit at 5V?

I'd like to power an Arduino using a supercapacitor. I already have that part of the circuit figured out. But I want to charge the supercapacitor using an external power source, without the ...
1 vote
0 answers
82 views

3 phase controlled soft starter and motor vibration

I want to make a soft starter for 3 phase induction motors. TRs are SCR pairs and ZCs are the zero-cross timing respect to line voltages (400V), not phase voltages (230V). I control the firing angle ...
7 votes
2 answers
1k 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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1 answer
212 views

Can a Triac be driven using only positive voltage due to the laws of Q1 and Q4 quadrants?

I have a BTA12-600B Triac and an Arduino. Is it possible I can trigger both positive and negative amplitudes of an AC cycle by suppling only a positive voltage from the Arduino digital pin to the ...
0 votes
1 answer
2k views

How to install a scr model in ltspice

I have downloaded an scr model file from this website and pasted it in the same folder as that of my .asc file. But ltspice still shows unknown subcircuit called for the scr present. What am I doing ...
5 votes
1 answer
500 views

How does this regulator/rectifier circuit work?

I am working with the following circuit from a motorcycle. It provides 13.8V DC out from a 15V-100V AC generator input. I understand how the bridge rectifier (BR1) and smoothing capacitors (C1, C2) ...
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1 answer
71 views

SCR vs diode VI characteristics

We know in an SCR when in conduction mode, triggered by some gate voltage, the lower three junctions will essentially turn into a single N junction and so the SCR essentially becomes a PN junction ...
1 vote
1 answer
183 views

Confusion in minimum gate triggering current of SCR

I was reading an article about working and properties of SCR from eleccircuit.com and in a section How to pick a SCR -it is written that we should check its rating and one of the mentioned rating in ...
3 votes
2 answers
507 views

Is this component in falstad a tl431

I'm self studying electronics, I am now familiarizing myself with the tl431, which is pretty much a "variable zener" aparently. I was shown the following symbol. I would like to simulate ...
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1 answer
179 views

Scr threshold voltage

recently I was going through a thyristor's data sheet, I saw one unfamiliar parameter called "threshold voltage " , can somebody explain what it is?
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1 answer
63 views

reversed-functioned scr

Like in a scr say in thyristors or triacs we know we can turn the scr "on" after a certain anode-cathode break-over voltage depending on the current present at the gate.But I want to know ...
0 votes
0 answers
39 views

How can I calculate the RMS and Medium Voltage in a Controlled Three-phase Full-Wave Rectifier?

I want to calculate Vrms and Vmedium for the angles of 30º, 90º and 150º on the circuit above with and current source and a resistor load. I found a variety of formulas on the internet, but them all ...
0 votes
3 answers
3k views

Wiring for 10000W 220V SCR Voltage Regulator Speed Controller

I live in the US and have the Twist Lock Electrical Plug 4 Wire, 30 Amps, 125/250V, NEMA L14-30P. It has 2 hots, 1 ground, and 1 neutral wire. I saw the following scr controller on ebay and am ...
0 votes
2 answers
461 views

Debugging a battery charger circuit

I have built a circuit of a battery charger here. Here is the circuit in the original project: However, it doesn't seem to work. The output I measure at the battery charging clips is only 1.2 V or so ...
-1 votes
1 answer
290 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 ...
0 votes
1 answer
268 views

Triac phase control

It's a triac phase control circuit, my book says. I know the conduction angle or the firing angle can be adjusted by adjusting the gate current in both cycles. but the question is what is the purpose ...
2 votes
1 answer
152 views

Scr gate resistor

as we know in transistors, current controls current, in JFET voltage controls current, but how about SCR? I have learnt that the gate can be triggered using both voltage and current (called gate ...
4 votes
2 answers
800 views

Why does diode keep conducting even after voltage across it is negative

consider single phase two pulse semiconverter asymmetric configuration. simulate this circuit – Schematic created using CircuitLab Note the high value of inductance L1. Let ...
0 votes
1 answer
245 views

Holding Current and Latching Current dilemma

I have gone through lots of resources looking up for holding current and latching current. All I can get is: Latching current is the minimum current that is required to maintain the "on" ...
0 votes
1 answer
94 views

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 ...