High pulse power resistors

[pjd3]

Hello all,

Are any of you aware of brand name power resistors (2-3 watt as we use for power node distribution) that are know for high pulse undurance ratings?

This isn't even for amps, its for my job and they stopped producing these types of resistors used in our life saving medical units. So far most have failed, as far as the various new ones we have tried.

Thanks!
Best,
Phil

[gktamps]

Would carbon comp resistors work for you? They are rated for high pulse, correct?

[pjd3]

Thank you for stopping by.

There was definitely conversation about those resistors handling pulse well but, not alot of confidence in them in terms of temp stability. I'm pretty sure that they are looking toward wire wound or ceramic.


Best
Phil D

[Reeltarded]

This is something Dave had a lot of recent experience with. I bet when he gets finished playing his fancy music he might chime in.

[pjd3]

thanks guys.

Just for more specifics, these are 10 ohm resistors (need to be +/- 10%).

The problems seem to be both associated with heat causing problems with the end caps, and voltage not distributing evenly from one end of the resistor to the other end. This is my first introduction to all the issues that a resistor can have from hard and fast edge pulses. the engineers tell (I'm a tech) that the heat build so quickly at a location that the resistor cannot diffuse that heat quickly enough to not have the kind of damage that occurs from that kind of incident. We've tried some Ohmite, TE Connectivity, First ohm, HVR Advanced but, they all exibited unacceptable results from blowing up to drifting in value too much after specified amount of applied pulses (355vdc/5000 pulses).
So yeah, it doesn't seem like there are many obvious candidates. They may have been going for some of the more affordable resistors but, if none of those fit the bill, then they/we may have to look at better and more expensive resistors for this aggressive application. These are those machines that get peoples hearts beating once again.

Thank you very much for your input.

Best,
Phil D

[didit]

Maybe https://www.prpinc.com/pr9481-series? Maybe insufficient voltage rating.

..

[sluckey]

Post a pic of one of these resistors laying next to a ruler so we can get a sense of physical size. Also post the original manufacturer and specs for the resistor.

[pjd3]

Thanks Sluckey, I'll see what I can do but can say that the resistors used in these devices seem to be very close the the size and types that we use for power nodes in our tube amps - 2-3 watt, ceramic or wirewound, axial.

I would need to dig a bit but, I don't expect anyone to do research on this for me, really just seeing if there are any manufacturers that may be known to have more stringent specifications on these type of power resistors, especially regarding pulse immunity.

Thanks,
Best,
Phil D,

[sluckey]

Tell your engineers to talk with some FAA radar engineers.

[Reeltarded]

Thanks Sluckey, I'll see what I can do but can say that the resistors used in these devices seem to be very close the the size and types that we use for power nodes in our tube amps - 2-3 watt, ceramic or wirewound, axial.

I would need to dig a bit but, I don't expect anyone to do research on this for me, really just seeing if there are any manufacturers that may be known to have more stringent specifications on these type of power resistors, especially regarding pulse immunity.

Thanks,
Best,
Phil D,

There is a Vishay line that I have recently purchased from CE. 2 and 3w versions and 5%. hold on.. PR03 is the number.

I read something about other specs but I can't find the page in my faves. These are supposed to be well underrated in many respects. They are small and tanky.

[pjd3]

Thank you everyone, I am passing this by the supporting engineer as these come in.

The Eng said he did look into the Vishay line for something very similar that Reeltard recommended but said there was a stock issue for the amount that would be needed. There are over 1000 of these units now sitting in the racks down in Manf. just waiting for something that will work (that wont kill a client!).

Thank you so much,

Phil D

[John_P_WI]

Hey Phil,

I came out of the same industry and used 10k 1 watt carbon comps which became unobtanium, and which the supplier admitted only 3 factories in China were making them - and they were shite.

The analog guys ended up using metal oxide in their place, specifically designed for the defib impulse. Sorry, don't remember the manufacturer, been retired from that industry for a number of years.

John

[pjd3]

Thank you John, and all.

Its become worrisome here. Unfortunately, the resistors that were working well stopped being manufactured, and, the ones we have tried don't even appear to live up to the manufacturers specs - even very much below the toted energy levels that they claim to handle. The engineers had me embed some of these in epoxy and sand them down to look at cross section at various depths. You can clearly see that end caps are not formed and attached well, that expected layers between sections are not fully there, causing arc inviting spaces. (and many of them did spark and blow, well below the energy joule spec). All sort of little issues that make them risky and inconsistent for these life saving devices. I thought I'd come here just to try to be a help if possible but, its looking like good resistors are getting hard to find, especially for application like this.

Thank you,
Phil D,