×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Question about non-automatic transfer switch

Question about non-automatic transfer switch

Question about non-automatic transfer switch

(OP)
hi,
   i want to design non-automatic transfer switch by 2 contactors and push buttons.
my question is do i need mechanical between the 2 contactors? or it is enough to work with NO-NC for both contactors.
   please help me

RE: Question about non-automatic transfer switch

Go buy a commercially built transfer switch.

Big multipole switches rated up to at least a couple of hundred amps are available from the likes of Craig & Derricott, Kraus & Naimer, and a few others.

If you use contactors then you need a mechanical interlock. Personally I'd also use electrical interlock backed up by a mechanical interlock: a plain mechanical interlock usually results in a cooked contactor coil if the interlock comes into play.
  

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

RE: Question about non-automatic transfer switch

Not sure what your application is sayedahmed but I've done the auxiliary contact method many times with good success.  Often I've had applications needing three or four sources all hooked to the same load.  You may end up with a mind numbing interlock circuit but it can work.  In some situations just interlocking may not be adequate.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Question about non-automatic transfer switch

If the result of a mistaken closure of both contactors will have a risk of life and limb, use both mechanical and electrical interlocks. Contacts weld, interlocks jam. Having both decreases the odds of a mistake dramatically.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Question about non-automatic transfer switch

(OP)
thanks all for reply.
  I need this to work between generator and main , it is not manual with handle and also not ATS.
  can i count on wiring the NO for the first contactor with NC for the second contactor and vice versa
so when the first is on the second is off and when the second is on the first is off.
 i don't want the main power get into the generator

RE: Question about non-automatic transfer switch

Why not use a change over switch?

RE: Question about non-automatic transfer switch

I have seen the damage that results when just electrical interlocks "Should have been enough." but weren't. Use a mechanical interlock, use the N/C contacts on the contactors, cross wired, and consider using cross connected N/C contacts on the push buttons. Also consider an off button that must be pushed before a transfer may be made.  

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Question about non-automatic transfer switch

(OP)
Thanks all,
  I think change over switch is more a Appropriate
   also i will use mechanical interlock

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources