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.
Questions tagged [scr]
186 questions
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Why in the world would the tab on a TO-220 package have a connection to anything (but GND, if applicable)?
I know this is in some way a different version of the prior question In i.e. a TO-220 package, why is mounting the (pin connected) tab to case safe?
But I am not looking for ideas what to do to mount a TO-220 (in my case an SCR that has the anode…
Gunther Schadow
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SCR in this circuit exploded - why?
Some of our boards have a damaged SCR. I just witnessed one in person today.
The SCR actually exploded upon power-on. A part of its packaging material just flew off along with an exploding sound. The resulting dead body of the SCR is shown…
Brian Wang
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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 any thyristor ought to be possible to turn off, by…
Hearth
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Why are bulky SCR power controllers used when the same can be achieved with a relay?
This is kinda noob question. I recently got an SCR Power controller (WATLOW DIN-a-mite DB20-24CO-0000 Style B). This is the first time I actually got to test an SCR controller for myself. The input trigger is 4VDC to 32VDC, which I powered with a…
The_Vintage_Collector
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Insulated gate SCR, does it exist?
Is there such a thing as an insulated gate SCR or anything fitting that description?
Brian Kubera
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How can SCRs be effectively paralleled?
I'm designing a precharge circuit which will carry 200A when closed. I'd like to use MCO150 Silicon Controlled Rectifiers, but they won't handle the current. Two in parallel looks like the most cost-effective way to handle the current I need.…
Stephen Collings
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Why would a "power switch" be designed this way?
This unit is an ARINC 429 bus analyzer, manufacturer "AIT" (Aircraft Interface Technologies), model "429A". Yes, it's confusing. Rated 115VAC/3A/60-440Hz. It has a 250W SMPS inside with several 3A fuses integrated. The power switch is a C&K…
rdtsc
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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.
However, I have also come across the \$i^2\sqrt{t}\$…
Oneneo
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Ideal component to switch 84V DC?
I wanted to control a 84V LED strip using a ATtiny13a microcontroller with minimal power wasted. I just want to turn it on and off, don't need any PWM dimming. The strip uses 270mA current and is about 22W power. MCU will be getting around 5V and…
Kokachi
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Is there a good reason to use an SCR based speed controller instead of a TRIAC?
I tried to purchase a switch for a reciprocating saw with variable speed for my Dewalt DW304. I discovered the part is no longer available.
Instead, I bought a similar switch used on the later model DW304PK. Its electronic, however, baffles me. The…
user148298
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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 circumstances where that is not true? Are there…
Stephen Collings
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Why do we bother with SCRs?
As far as I know, SCRs are basically the DC-only cousin of a TRIAC. However, in my travels I have not encountered a TRIAC being much different in price than a similarly spec'd SCR, so I guess I don't really understand the point of SCRs from an…
Brendan Simpson
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what is a thyristor
As part of my 2330 lv3 am required to know about thyristors.
I just want to confirm my understanding is correct. A thyristor is basically similar to a transistor, only it stays switched on when it's trigged for as long as there isn't a break in the…
Ageis
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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 that long "trailing" (or back porch) current is…
jf_vt
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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) work, but I am not clear how the SCRs are being…
user8908459
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