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Chilla
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Join Date: May 2009
Posts: 2

Switchboard Design - Form Categories

05/18/2009 2:10 AM

Australia uses IEC 600430-1:1999 as the basis for its low voltage switchboard standard and has sub-categories Forms 2a, 2b, 3a, 3b, 4a and 4b.

I would like to know typical examples of where each of these sub-categories would be specified. For example, I do not see Form 1 and Form 2a having a place in a heavy industrial installation, and Form 2b may be used for non-essential light and power distribution boards and similar.

I am used to seeing Form 3b for high reliability MCCs such as water treatment facilities. I have no personal experience of seeing Form 4 specified.

If anyone has actual experience in specifying forms 3a, 3b, 4a and 4b I would like to hear from you on typical applications for each.
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david.b.ie4u
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Join Date: May 2009
Posts: 5
#1

Re: Switchboard Design - Form Categories

05/19/2009 7:03 AM

The main difference between form 3a/b and form 4a/b is that in the form 4 option, the terminals for external / field cables of a functional unit are segregated from those of other functional units.

In form 4a the terminals are located in the relevant compartment of the functional unit, which requires the field cables to enter the compartment. In form 4b the terminals are located in their own, separate compartment, usually adjacent the relevant functional unit, in the cable way.

Form 4 gives improved protection against contact with live parts. This would allow safer maintenance access to a unit while other parts of the switchboard are still live.
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Anonymous Poster
#2
In reply to #1

Re: Switchboard Design - Form Categories

05/19/2009 8:32 AM

Thanks - that is useful
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