# EPO/Shunt trip; and trade books biblio



## HARRY304E (Sep 15, 2010)

Zaped said:


> Where online to find wire diagram for EPO/shunt trip circuit wires ? Also, does anybody anywhere, including online, provide any significant BIBLIOGRAHY OF BOOKS useful in the electrical trade ? Also of interest, bibliography including short reviews of evaluations of electrical trade books listed.


http://www.teal.com/newsletter/AppsNote16.pdf


http://www.nfpa.org/catalog/category.asp?category_name=NFPA 70E Resources | Texts/Handbooks


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## Zaped (Jul 6, 2008)

*multiple epo switches, etc...*

Thanks Harry304E for the pertinent information. Nice. Any such online diagram for the following variation would also be of interest: an EPO/shunt trip situation where there are multiple EPO switches, say three, and the shunt trip coil circuit is powered from two phases of the same 480v circuit as powers the power circuit, but is stepped down to 120v by transformer ahead of the epo switches and shunt trip coil.


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## MDShunk (Jan 7, 2007)

Zaped said:


> Thanks Harry304E for the pertinent information. Nice. Any such online diagram for the following variation would also be of interest: an EPO/shunt trip situation where there are multiple EPO switches, say three, and the shunt trip coil circuit is powered from two phases of the same 480v circuit as powers the power circuit, but is stepped down to 120v by transformer ahead of the epo switches and shunt trip coil.


One leg of the transformer secondary goes to the shunt trip coil. The three n/o EPO pushbuttons are placed in parallel, and their line side is connected to the other wire of the transformer secondary and their load side is connected to the other wire of the shunt trip coil.

Think of this as three doorbell buttons going to one chime unit.


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## leland (Dec 28, 2007)

MDShunk said:


> One leg of the transformer secondary goes to the shunt trip coil. The three n/o EPO pushbuttons are placed in parallel, and their line side is connected to the other wire of the transformer secondary and their load side is connected to the other wire of the shunt trip coil.
> 
> Think of this as three doorbell buttons going to one chime unit.



Now for some fun(after you get the basics) Check out some EMO-Emergency motor off-ckts for manufacturing/production.

Most basic ckts on these, are Norm/closed,when opened the production line stops.

I have run across some that use N/O and N/C, that can be a challenge to trouble shoot with out information/schematics.


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## MDShunk (Jan 7, 2007)

Yeah. Guard switches are n/c and n/o in one package, and go back to a specialized safety relay Drives normally are fitted with a "safe off relay" if turning them off is critical from a safety standpoint. 

When I hear EPO though, I generally think of IT rooms, machine shops, and gas pump islands. If you really want to do an EPO with n/c contacts, use an undervoltage release breaker with a momentary push button at the panel that gets held in while you reset the breaker. That's the easiest way I've found.


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