# SCR question

Discussion in 'General Electronics Discussion' started by hyudryu, Mar 13, 2010.

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1. ### hyudryu

64
0
Feb 24, 2010
I found a MCR265 10 and it says 55A. It also sais it can withstand a 550A surge. Why doesn't it just say 800V 550A instead of 55A? Also, how does it withstand 550A? that can melt copper

2. ### Mitchekj

288
0
Jan 24, 2010
You'll find a time limitation on it's surge rating. 55A continuous, 550A when subjected to the following precise conditions:

Peak Non-repetitive Surge Current — 8.3 ms
(1/2 Cycle, Sine Wave)

Even then, I'd not run even near that current through it.

25,500
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Jan 21, 2010

4. ### hyudryu

64
0
Feb 24, 2010

I measured around 200A. Im scared

5. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Why?

Did you...

Really, if you're working on something that has the potential to kill yourself, I would expect that you at least calculate a single value. Is that too much to ask?

Let me calculate one for you -- the peak power coming from that capacitor. 300V at 200A is 60,000 watts. Yep, 60kW. This presumes that you were able to accurately measure the current, which I think is unlikely. I would not be surprised if the values were even higher.

I just measured the ESR of a typical capacitor used in a camera flash unit. It is 0.13 ohms. That means, if short circuited, at 300V it could potentially deliver over 2000 amps. (that's Ohms law, you should look it up -- There's a calculator on this site). Whilst there are other factors which mean it would never actually reach that level, it's an indication of the amount of current these can deliver for a short period of time.

Here and here are some things you should read.

Last edited: Mar 15, 2010
6. ### hyudryu

64
0
Feb 24, 2010
I knew all of that stuff already. I will go look for the thyristor you suggested that was 47\$
Well, Thanks anyways

7. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,500
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Jan 21, 2010
3 points

1) I said "something like" that. You may be able to find a cheaper part (it was simply the first in the list)

2) You may have calculated those figures, but from your responses (certainly by the apparent surprise at 200A) I'm not sure that you did. I'm extremely certain that you have not either understood, nor taken steps to mitigate for, the energy stored in your coil after the capacitor is discharged.

3) You unwillingness to answer questions about how you achieved certain things means that I really can't help you any more. The risk of the gap between your reality and what I perceive you're saying may be wide enough that my well intentioned advice may be completely wrong.

8. ### hyudryu

64
0
Feb 24, 2010
I bought a NTE54004 SCR it is 1000V 55A 550A surge. I can't seem to find a datasheet that has the info on the pin assignment Please help

9. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,500
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Jan 21, 2010
1) Am I not clear?

2) Have you never heard of google?