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Registered Member #1339
Joined: Wed Feb 20 2008, 04:43PM
Location:
Posts: 9
I need to measure the long term drift of some Caddock precision resistors. I don't have a decent DC power supply to source the load but I do have an AC xfmr with enough current.
My ?, Do you think the RMS value across the resistors will give a good approximation of the performance. My test values are as follows
7.5M TG931, 3.75KVDC for 1000HRS (Yes I know this is out of the MFG rating)
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
I do not think that the results for ac and dc will be the same as any migration or growth effects would not be evident in the ac case. Just use rectifier(s) and capacitor(s) as required.
Don't forget that at kilovolts dust/soot and other contaminants will be attracted and will probably be the principal cause of failure, along with humidity and/or condensation effects.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068
You should be able to calculate all this.
Just get all the manufacturer's specs on the resistors - they should give you tolerances for practically everything you need. Then use all those tolerance values (humidity, temperature, soldering heat, etc...) and do an RSS analysis to get an appropriate tolerance value.
Registered Member #1339
Joined: Wed Feb 20 2008, 04:43PM
Location:
Posts: 9
Sulaiman wrote ...
I do not think that the results for ac and dc will be the same as any migration or growth effects would not be evident in the ac case. Just use rectifier(s) and capacitor(s) as required.
Don't forget that at kilovolts dust/soot and other contaminants will be attracted and will probably be the principal cause of failure, along with humidity and/or condensation effects.
I tend to agree with you about the behavior of DC vs. AC, if it were a heat only effect then it might be the same. These will be tested in an clean SF6 environment to contamination will not be a problem. Thanks for the comments, I'll post my results when I get them in case anyone is interested.
Registered Member #1339
Joined: Wed Feb 20 2008, 04:43PM
Location:
Posts: 9
Dr. Shock wrote ...
You should be able to calculate all this.
Just get all the manufacturer's specs on the resistors - they should give you tolerances for practically everything you need. Then use all those tolerance values (humidity, temperature, soldering heat, etc...) and do an RSS analysis to get an appropriate tolerance value.
Dr, I do have the specs, the issue is we are using these at about 1.8 X the mfg rating. Fortunatly Caddock is very conservative with thier ratings but I need to get a ball park prediction of the possible drift at these levels.
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Stability testing of HV resistors
