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Joined: Nov 2005
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shiju Offline OP
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Respected all,
THanks for helping me out. You had helped me find out the out the source for the capacitor and also the way out in case of unavailability of this capacitor. Hope to repair those incubators soon.

Thanks again

shiju

Joined: Mar 2005
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Dear Shiju,
did you get the capacitor and fix the problem?
Regards
Sajeev

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shiju Offline OP
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hello sir ,
we could arrange for the capacitor , we have already received the quotation for that from a company to which i gave the address i got from the seniors in this site, as we cant import dirctly from anyother country. Its rate is coming something around 2000 indian rupees. But still its not a high price when compared to the board which costs 46000 indian rupees.

and currently the machine is working (in the biomedical, and not with the patient )with the substitute as suggested by some members here in this forum.

bye sir,
shiju

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Dear Shiju,
Nice Work and saving. Hope the Arabians recognize your talents and hard work.We are proud of all you keralites who show the values to the world.
Best of luck.
Regards
Sajeev

Joined: Feb 2005
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I know what your all thinking but don't think this one is going to go away!

Has anyone out there managed to find a supplier for these Roe 68uF bipolar capacitors.

I have a incubator down at the moment and due to the age of these incubators I think it may be the first of many!

The incubator is still supported by Draeger, but as we know only to board level in most cases.

Anybody out there made and further progress on this and would like to share amongst friends?

All the best for the new year!

Stuart

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Super Hero
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There has to be a better way! Didn't anyone try Grahame Driver's approach (which sounded OK to me)? Any fires yet, Grahame? smile


If you don't inspect ... don't expect.
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Hi folks,
I substituted a series / parallel combination (2 in series with 1 in parallel) of 100v 47uF bi-polar capacitors from CPC, part number CA01894.
The combination capacitance was ~70uF near enough for our purpose.
It worked fine for about 5 months on a 16 year old incubator. During a routine service of the incubator, the capacitor combination was checked, revealing a slight swelling to the single capacitor.
Investigation and more research indicated that the capacitors could not cope with the ripple current (capacitor maximum rated as 250mA) the motor current through the capacitor combination was measured at 480mA.
The brain, using the capacitive reactance formulae, summised that twice as much current (320mA) was passing through the single capacitor than the series combination (160mA) and stressing the case, hence the swelling.

The jury is still out on whether the capacitor would have eventually burst.

I hope this helps any budding designers.
Pete

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That’s more like it, Pete. But brave of you to post that on this forum, though, Mate! smile


If you don't inspect ... don't expect.
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Huw Offline
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Sorry, don't follow you there Geoff.
...or am I being thicker than usual?

Unless it's the reference to near enough for our purpose - which is the sort of thing I will admit to having done myself.

A
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Hi Pete,

Quote:
The jury is still out on whether the capacitor would have eventually burst.
I think it's fair to say that electrical/electronic components operated beyond their specified operating conditions are more likely to fail within the MTTF that's been established by the component manufacturer. The problem we face when replacing any component, that's not a like-for-like substitution, is whether the component we fit actually meets or exceeds the specification of the original one.

Assuming the designer has selected a component to give an acceptable overall MTBF for the system then if we select a component that's not up to the job then at best we reduce the reliability of the system and at worst it may fail in a way that's unexpected, e.g. pop, bang, burn, etc.
Reliabilty testing in service is not a particularly good way of checking if the choice of a component is Ok in my opinion (particularly not higher power components) - you didn't say whether the incubator had been put back into service or not - capacitiors can give off some nasty fumes and smells when they vent off that're likely to be toxic if they start to burn.

At least the designer has the luxury of testing during R&D to make sure their choices do not adversely affect reliability or cause harm and it's their job, I suppose, when all's said and done. Personally I'd use the justification for a lack of a replacement component to force a purchase since, invariably, I've found that when push comes to shove the NHS can always find the money to replace equipment if it's really needed.

Just giving my views and opinions, that's all.

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