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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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Pulse DC reading

I'm trying to read current with INA186 on low-side. The shunt resistor calculations are ok, but the current sensed, comes from a pulse DC signal of a SCR. This SCR is rectifying the output of a power ...
samuel mattio's user avatar
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What is the purpose of the Capacitor in this SCR trigger circuit?

I've seen this schematic for triggering an SCR. What is the purpose of the R2 and C1 in parallel with the primary winding? Is it just for back-emf? Why not use a diode? How do you calculate proper ...
Thomas C.'s user avatar
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Is it possible to shutdown SCR when high current is passing through it?

I have a project in which I need a controllable high voltage (400+ V) high current (10+ kA) pulse (from μs to ms.) Obviously FETs won't cut it because the high voltage will destroy the channel of any ...
7E10FC9A's user avatar
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1 answer
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Can I use an AC SCR to control a 180 V DC motor?

I want to control the speed of a 180 V treadmill DC motor the cheapest and easiest way. The motor will only run in one direction. It wil be powered by 220 V AC. Can I use an AC SCR speed controller ...
Islam Mouhsen's user avatar
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46 views

Structure of a thyristor

In the test of the thyristor (BT151S-500L) that I removed from the contactor driver (in the multimeter diode test phase), I saw that the gate-cathode voltage drop was 236mV, but the cathode-gate ...
Jundullah's user avatar
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0 answers
17 views

Quantifying the reduction in a thyristor's turn-off time in response to increasing reverse voltage: Seeking data or graphs

From a previous question of mine (here: What factors affect a thyristor's "circuit commutated turn-off time"?), which was asked about 5 years ago, a user presented this very helpful ...
CaptainFantastic's user avatar
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Testing a hockey puck SCR

I have a hockey puck SCR in my circuit which I suspect might be faulty. The reason I suspect the SCR is that while my system is charging up it discharges prematurely and arcs. I tested it with an ...
Shakiba HS's user avatar
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1 answer
149 views

Latching relay latches when button pressed, unlatches when power is restored

I am building a battery backup for my dashcam, I need to turn off battery when the car is parked for a long period. Instead of having a manual on/off switch I want to control the battery using a ...
Alex Robbin's user avatar
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1 answer
130 views

SCR phase control

I'm making a battery charger with phase control. While making the circuit I had some doubts. The transformer has a center tap, in this way I can make a full wave rectifier without diodes. Then ...
samuel mattio's user avatar
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2 answers
87 views

Turn on control of antiparallel SCRs to pass AC

If you are trying to pass an AC signal through antiparallel SCRs (there to isolate the signal when required) where the AC frequency is low enough to satisfy the turn-off time requirements during the ...
Paul's user avatar
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Is it possible to design an over/under AC voltage protection circuit using only diodes and SCRs?

Is it possible to design a circuit using only SCRs and diodes (Zener or otherwise) as a main regulating device to protect a load (220 V, 80 W) from over- and undervoltage? Other passive components (...
Yeal Takian's user avatar
5 votes
2 answers
402 views

Mounting an 11W SCR with a Flat Profile

I have two SCRs in my design that will be switching up to 15A at 120-240VAC. The two devices will split the power, with each one conducting a half cycle. I'm considering using the S6025 by Littelfuse. ...
user120632's user avatar
0 votes
1 answer
73 views

Two SCR thyristor modules using gates tied together to trigger

When I tie the gates of a MCC 95-16 together, it conducts AC at decreasing gate milliamps as I raise input voltage. Is this acceptable to power a microwave transformer? My zero crossing opto driver at ...
callmemac's user avatar
1 vote
1 answer
291 views

Is this circuit sufficient?

Firstly I am sorry for this bad drawing but I just got it from the internet. Secondly I'll give a brief idea about the project it is a static switch would be used to drive general loads (inductive and ...
Hazardous Voltage's user avatar
1 vote
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117 views

Circuit Design For HDMI Shut Off

I am building a device that will turn on/off the HDMI to a monitor. This will allow a microcontroller to flip the monitor on and off. I tried a basic design that switches the 5V, DDC/CECGround, and ...
Joel Danowitz's user avatar
2 votes
1 answer
155 views

Switching only one AC side live/netural using Triac/SCR

I was wondering if Triacs/SCRs can be used for switching only one side of AC (neutral or live), or whether there are other component that I can use for this. The load is an AC motor, and the current ...
Mohamed El-Sayed's user avatar
2 votes
5 answers
4k views

DC motor speed control using SCR

I'm trying to design a DC motor speed control circuit using an SCR, where I want to control the speed of a DC motor like the way electric fans work by changing the fan speed. In this project we are ...
JOVIN SAN ANDRES's user avatar
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159 views

Is it possible to make a halfbridge coilgun with high side IGBT and low side SCRs?

In a rather simple coilgun, the problem of freewheeling current from the coil is solved with a diode in parallel with the coil. The energy of the reverse current is wasted this way and even slows the ...
kall gakr's user avatar
1 vote
1 answer
133 views

How to turn off charging while SCR is latching?

So I'm trying to make a CDI for my old motorcycle that can be controlled using Arduino, after a bit of research (mainly Googling) and prototyping I come up with this design, this design has been ...
collin power's user avatar
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2 answers
234 views

How does this half bridge inverter charger charge the battery?

I just can't understand how this inverter charger actually charges the battery. The charging circuit uses two SCRs on the mains side of the transformer. The same transformer is also used to step up ...
Abhishek's user avatar
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2 answers
67 views

Will Any SCR Trigger Optically If It Is Exposed To Light?

I read somewhere that all SCR's are photosensitive, in the same way that all diodes emit light, but some are optimized to take advantage of this property while others are not. There is an SCR I want ...
James Strieter's user avatar
2 votes
1 answer
138 views

Why is the SCR in this circuit switching off even though current is still above th holding current?

I am designing a circuit that controls DC power to a load through the use of SCR thyristors. I have been testing things out using the CLA20EF1200PZ part from Littelfuse. It has a 25 mA holding current ...
Ismail Assaidi's user avatar
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124 views

Budget friendly battery charger controlled by phase angle ( SCR )

My circuit circuit is below so you can understand what I'm saying. I want to make a lead battery charger that can control the charging voltage and current (no discharge.) I have a circuit that ...
samuel mattio's user avatar
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1 answer
61 views

Is It Possible To Choose a Higher Holding Current When Designing SCR?

I'm looking at this data sheet: SCR data sheet on Digikey This device seems perfect for what I want to do, with 1 exception: The holding current is way too low. Various forums have suggested that (on ...
James Strieter's user avatar
2 votes
1 answer
62 views

For sufficiently low duty cycle, can you get away with driving SCR above rated current as long as A^2 * s are maintained?

I'm wondering if the A^2-s rating of an SCR is what ultimately decides whether a given current for a given time is okay, even if the data sheet does not list such a number. For instance, right now I ...
James Strieter's user avatar
2 votes
0 answers
40 views

Can I use a voltage divider instead of an external battery with an SCR?

I have this circuit 12VDC battery boost converter up to 390V DC-DC capacitor 1000 uf 450V diode 10A10 thyristor BTW69-1200 (I gt 8-80 mA / V gt 1.5v max) I managed to make this circuit work with an ...
Tito's user avatar
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1 answer
2k views

SCR based rectifier vs IGBT based rectifier

I am wondering what is the difference in performance of rectifiers when used with SCR and IGBT. I searched on internet but all i can find is that IGBT is voltage triggered and SCR is current pulse ...
Pankit Shah's user avatar
1 vote
2 answers
440 views

Thyristor gate triggering issue

We are using an MOC3041 to trigger the gate of a thyristor (BT155Z-1200TQ). We use the circuit design from the datasheet of the MOC3041 (Figure 12: Inverse−Parallel SCR Driver Circuit). We detect zero ...
Nihan's user avatar
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2 votes
1 answer
770 views

How to make a driver circuit / trigger circuit /gate circuit for SCR?

Ii would like to ask you for help to understand the SCR, thanks in advance! I also hope this question helps another to understand this device too I have read about SCR in Boylestad book but it's ...
Cblue X's user avatar
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3 votes
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Can I make active devices share voltage equally using ad hoc shunt resistors?

I have 3 active devices in series, SCRs in this case but I'm guessing that's not important. Each is rated for 2.4 kV. The total voltage I will actually apply is 6.6 kV. Leakage current is guaranteed ...
James Strieter's user avatar
1 vote
2 answers
145 views

In practice, is the ganging of a large number of SCRs in parallel often more expensive than an equivalent hockey puck?

In a separate but related question, I asked how EEs normally wire a large number of SCRs in parallel for high current applications. For this 1 example (sample size = 1), I found a single hockey puck ...
James Strieter's user avatar
1 vote
2 answers
134 views

Can an SCR conduct backwards in large amounts while the gate is asserted?

I am driving an inductive load and have a situation where an SCR will be forward biased but conduct in reverse. Can it do that if I strobe the gate the entire time I want it to conduct in reverse? ...
James Strieter's user avatar
0 votes
1 answer
141 views

Requesting clarity on the di/dt rating of thyristors

simulate this circuit – Schematic created using CircuitLab I have a general question about thyristors. I know that the di/dt limitation of thyristors is due to high currents flowing through ...
CaptainFantastic's user avatar
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0 answers
50 views

Do commercial products exist for lab-scale thyristor triggering?

Hello fellow stack exchange members! We're excited about our novel high-voltage voltage-source-converter design that utilizes SCRs/thyristors and commutation circuits. We're now looking to build a ...
CaptainFantastic's user avatar
0 votes
1 answer
43 views

Different firing angles of SCR

Considering this circuit, what would happen if T1 and T2 had different firing angles, let's say 45° for T1 and 60° for T2? Is it the same thing as both of them having 60°? (I think that the circuit is ...
Nicolae Racheriu's user avatar
1 vote
2 answers
218 views

What is the purpose of the unijunction transistor in this circuit?

Trying to figure out the purpose and functionality of this circuit. Apparently, this is some sort of temperature controller. There is no information on parts values or the load type (heater, probably?)...
Jimmy Falcon's user avatar
1 vote
0 answers
54 views

Trying to get a 10uS pulse width to fire an SCR using a PIC16F884

I have the circuit built and running but I need to shorten the pulse width of the SCR. I am using a PIC16F884 running at 16MHz. I am using a half wave to control a device. When I use a for next loop, ...
Dorato's user avatar
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0 votes
0 answers
71 views

What is the most efficient circuit to control a 3-phase controlled rectifier circuit with the ability to control the firing angle?

I am trying to design a board to control a 3-phase full wave rectifier with the ability to control the firing angle (alpha) through a potentiometer or a selector, and I was wondering what are the most ...
Shamooooot's user avatar
0 votes
1 answer
132 views

Will swapping a SCR with an SSR increase max current?

We have a system at my work that controls a furnace via a NI cRIO. This circuit currently uses a SCR (model listed below) with the cRIO to switch power out to the furnace. I don't want to get into the ...
user3430541's user avatar
0 votes
3 answers
325 views

Calculating reactors for parallel connection of thyristors (SCRs)

I have been looking for more information on how to connect two thyristors in parallel in order to balance the load. From what I have found there are two options: either using balancing resistors, ...
Sumutiu Marius's user avatar
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0 answers
154 views

Difference between thyristor I(tsm) and I T(AV)

For example I have a capacitor send intermittent pulses to a coil send about 85A for few msec then off for 3-4 seconds (for 5mins) I was looking for a scr to switch it i found 40tps12 thyristor https:...
Tito's user avatar
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0 votes
2 answers
313 views

Connect two thyristor in parallel

I have 2 BTW69-1200 thyristor Vrrm = 1200 V Irms = 50 A I tsm (Non repetitive surge peak on-state current) = 610 (8.3 ms) - 580 (10 ms) Here is the datasheet https://pdf1.alldatasheet.com/datasheet-...
Tito's user avatar
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2 votes
2 answers
269 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 ...
phonetagger's user avatar
1 vote
1 answer
284 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 ...
PStechPaul's user avatar
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5 votes
2 answers
317 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 ...
jf_vt's user avatar
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0 answers
38 views

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 ...
OhtohV2's user avatar
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1 answer
177 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 ...
PabloL's user avatar
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0 votes
1 answer
297 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 ...
Shamooooot's user avatar
2 votes
1 answer
334 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.
Shamooooot's user avatar
1 vote
0 answers
190 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 ...
KHAN's user avatar
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