Lighting contactors that fail to closed position 1

[kzryder]

I am working on a project that requires all lighting to fail to the on position but since my contactors that are owner furnished are mechanical held contactors if I lose control it will remain in the last position held.
My question is is there a way to make a mechanicaly held contactor do this or will I have to change contactors to electronicaly held contactors.

 

[jraef]

If the requirement is to ALWAYS fail to an on state (sounds like a really bad idea to me, but whatever...), then the only way to ensure that is to use electrically held contactors with NC contacts.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[Skogsgurra]

There may be safety reasons. If a contactor coil burns or opens - or anything else fails - it is often good to still have light on. Not all sites have back up lighting with DC and then the second best way of doing it is to use the NC contacts that Jeff mentions.

Problem is that if you need high current, it is difficult to find NC contacts with same rating as NO contacts. Most contactors above 10 - 16 A still have NC contacts rated at 10 A.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ScottyUK]

There are contactors with large NC ratings, but they are almost always of the bar & shaft type rather than the more common block type. They are relatively expensive and quite large but are normally designed for severe duty so they are very suitable for AC-5 (lighting) and AC-6 (reactive) service. For example ABB's R-Line is good, Hubbell (used to?) have something similar, Telemecanique certainly do. NC ratings of at least 400A are available, which equates to a hell of a lot of lighting.


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If we learn from our mistakes I'm getting a great education!

 

[jraef]

Here in the US, specialized "Lighting Contactors" are available from several mfrs that have replaceable / convertible contacts, i.e. you can buy the contactor with NO or NC contacts and stack additional power poles onto them that are either NO or NC, usually up to 12 poles maximum, 20, 30 or 60A.

http://ecatalog.squared.com/pubs/Motor Control/Lighting Contactors/8903CT9701.pdf

http://cmsapps.sea.siemens.com/controls/icc2010/10IndControl_ pdfs/10IC_08/08_069-071.pdf

"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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