resistor power rating

M

MHsu

Guest
I am working on a small project, I have to choose SMT resistor, I
encountered some questions.

Can I add 500v through 47 ohm (11A) carbon composition resistor for 1ms?
that resistor is form ohmit SMT RC series, on the spec it says can go 6.2 x
Power rating for 5s.

How hard can I over drive Panasonic SMT anti-surge resistor or thick film
resistor? If I take 1W 1.2k sistor, can I over drive 5 times(5W) for .1s,
14 times (14W) for 1ms?

Any inputs are greatly appreciated

Best Regards

Mhsu
 
MHsu wrote:
I am working on a small project, I have to choose SMT resistor, I
encountered some questions.

Can I add 500v through 47 ohm (11A) carbon composition resistor for 1ms?
that resistor is form ohmit SMT RC series, on the spec it says can go 6.2 x
Power rating for 5s.

How hard can I over drive Panasonic SMT anti-surge resistor or thick film
resistor? If I take 1W 1.2k sistor, can I over drive 5 times(5W) for .1s,
14 times (14W) for 1ms?

Any inputs are greatly appreciated

Best Regards

Mhsu
Resistors have a power rating and a voltage rating.
The highest voltage rating for a "common" SMT resistor is 200V (1206
size Yaego)
The power rating of that size is 0.25W.
Zapping a resistor with excessive power and voltage would result in a
rather short useble lifetime, and the result might be a burned track on
the surface ("short").

The Panasonic 2512 SMT resitors have a power rating of 1W, but still a
200V rating (overload rating of 400V).
Their "Anti-Surge" resistors max out at 0.5W; again a 200V rating
(overload rating of 400V).

If you want any semblance of reliability, put them in series so that
the absolute maximum voltage that any given resistor "sees" is 200v, and
that the peak power applied to any one of them is 0.5W.

If you want a resistor to act like a fuse under fault conditions, use
a carbon composition resistor.
They give a visual indication (get brown or black or "pregnant" or
crack or combinations), and the nose can also detect the "burnt"
condition.
 
On Tue, 04 May 2004 05:06:54 GMT, "MHsu" <toronto888888@hotmail.com>
wrote:

I am working on a small project, I have to choose SMT resistor, I
encountered some questions.

Can I add 500v through 47 ohm (11A) carbon composition resistor for 1ms?
that resistor is form ohmit SMT RC series, on the spec it says can go 6.2 x
Power rating for 5s.

How hard can I over drive Panasonic SMT anti-surge resistor or thick film
resistor? If I take 1W 1.2k sistor, can I over drive 5 times(5W) for .1s,
14 times (14W) for 1ms?

Any inputs are greatly appreciated

Best Regards

Mhsu
I posted some resistor abuse notes here on Feb 27... google groups
should have it.

John
 
Hi Mhsu,

Before releasing any of this into a product I suggest to obtain info from the
manufacturer. With surges this high there can be some very unforeseeable
effects similar to electro migration and the manufacturers know best what their
particular chemistry will do.

I had to pulse resistors in the past as well and found that especially the
smaller manufacturers are pretty open to discussions.

Regards, Joerg
http://www.analogconsultants.com
 

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