Maker Pro
Maker Pro

SCR question

Status
Not open for further replies.

hyudryu

Feb 24, 2010
64
Joined
Feb 24, 2010
Messages
64
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
 

Mitchekj

Jan 24, 2010
288
Joined
Jan 24, 2010
Messages
288
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.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Please refer to this thread for more information.

Answering the questions posted there will help you determine the max current.

Yes but i measured my coil and it is 1.3 ohms and i figured it would take up some current for the magnetic flux so it probably wont be 600A.

Use ohms law to calculate the maximum current. For 300V and 1.3 ohms what is that?

Have you measured the inductance of the coil? Will it saturate at a current less than the maximum allowed by the resistance of the coil? Given the charge stored in the capacitor, the resistance of the coil and its inductance, how fast will the current rise, and what will its peak value be?

You need to be able to answer most (if not all) of these questions.

But to be safe, i will solder 3 of them parallel so it won't burn out.

It doesn't work that way. You can almost guarantee that one device will hog all of the current. The other problem is triggering all of the devices at *exactly* the same time.

You're better off with a device that can handle the current. I'd be looking at something more like this http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=ST230C04C0-ND

For the 2N6504 when i googled it, the datasheet was 50V 300A surge... does the 2N6508 have a 300A surge also?For my capacitors, they drain pretty fast. when i connect wires, the wires melt onto each other and the power drains all in a few milliseconds

How did you measure the discharge time?

From that time, how did you calculate the current?

And should i use lead solder? I read today that lead solder creates lead oxide gas which can give you lead poisoning. I made a fume extractor but i still dont want to risk it. Is it safe? So first, i got a laptop fan, i put pet store bought active carbon rocks and i put them inside a sack and put it at the end of the fan so the air goes through the active carbon. I tried lighting a match and it filtered out about 70-83.5% of the smoke.

87.93% of statistics are made up.

Don't worry too much about lead poisoning from leaded solder. Most of the smoke is the flux and it's visible. Just work in a ventilated place.


1 more question, If i bought a sealed lead acid battery that is 5AH and is at 2V. How do i charge it? Do i just turn the voltage to 2V on my power supply and plug it on? + to + and - to -?

kinda... Look up the specs for the battery.

For a given temperature it will specify a charging voltage and current. Set your power supply to that voltage (it may be 2.35V) and set the current limit to a value no greater than the charge current. The battery will initially charge at the current you have set your PSU to and eventually this will reduce as the voltage on the battery rises.

Beware of any charging restrictions that may apply (see the data sheet)

If your power supply does not have a current limit (not a rating, a variable current limit) then you can manually adjust the voltage to achieve a suitable charge rate, but it's a tedious process, prone to error, and not recommended.
 

hyudryu

Feb 24, 2010
64
Joined
Feb 24, 2010
Messages
64
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.


I measured around 200A. Im scared
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
I measured around 200A. Im scared

Why?

Did you...

Use ohms law to calculate the maximum current. For 300V and 1.3 ohms what is that?

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:

hyudryu

Feb 24, 2010
64
Joined
Feb 24, 2010
Messages
64
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.

I knew all of that stuff already. I will go look for the thyristor you suggested that was 47$
Well, Thanks anyways
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
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.
 

hyudryu

Feb 24, 2010
64
Joined
Feb 24, 2010
Messages
64
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.

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
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
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

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.

1) Am I not clear?

2) Have you never heard of google?
 
Status
Not open for further replies.
Top