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agrima.joshua
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Join Date: Oct 2012
Posts: 8

Convection Inside Electrical Enclosure

10/31/2012 5:22 AM

Problem : An electrical panel(figure of real product on left hand side) Dimensions - 400X450 mm, depth - 100 mm encloses the following components - busbars (3mm thick), modular devices etc. In temperature rise test (IEC:2009 61439), the enclosure exhibits ambient of upto 104 C (initial ambient is 50 C).

1.) What are the various sources of heat (as of now, we know I^2*R for copper busbars)?

2.)How is the enclosure ambient absorbing heat (through convection or radiation)?

3.) How does one analyse accurately, the heat transfer mechanism?
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Pathfinder Tags: Convcetion coefficient of electrical panel temperature rise test
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PWSlack
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#1

Re: Convection inside electrical enclosure

10/31/2012 5:42 AM

A1) Check all connections inside the enclosure are "clean, tight and bright". Otherwise insulation materials are going to degenerate.

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lyn
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#2

Re: Convection inside electrical enclosure

10/31/2012 8:10 AM

1) Anything hotter than the surrounding environment.

2) Yes, and conduction.

3) Measure it accurately.
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Yahlasit
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Location: Cd. Juarez, Chihuahua, Mexico.
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#3

Re: Convection inside electrical enclosure

10/31/2012 8:47 AM

I have seen heat build-up, false contacts, charred insulations, breakers tripping and loss of one phase, all due to poor tightening; this causes carbon deposits and makes copper less conductive, requiring a good scrap and clean or even cut off and strip to remake the conection.

Take out the back plane, start checking joint screws' torque, right from the incomming busbars, all the way to the last circuit breaker in your box.

Use a clamp-on Amp. meter to make sure you're not exceding the rated current for each wire gauge in your panel.

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Ried
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Join Date: Dec 2005
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#4

Re: Convection Inside Electrical Enclosure

10/31/2012 11:22 PM

Besides the numerous CBs, what other devices in this panel have of cause a voltage drop? Any voltage drops (undersize conductors, loose terminals, resistors, etc.) will generate heat.

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brettj1au
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#5

Re: Convection Inside Electrical Enclosure

11/01/2012 2:04 AM

First thing I'd be doing is going to my box of meters & getting my non contact IR thermometer & finding out where the hot spot is to establish where the heat is being created. Once this has been identified take the appropriate action as the other posters have said.
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