×
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

UPS Power distribution - Selective coordination of protective devices

UPS Power distribution - Selective coordination of protective devices

UPS Power distribution - Selective coordination of protective devices

(OP)
Good day!

I would like to know anyone has some good write up or share some experience on the Selective coordination of protective devices for UPS Power distribution.

What are the aspects to be considered for selectivity study?

My UPS rating is 40kVA and the system voltage is 110V AC, 1-phase. I am not sure whether one of the conductor is earthed or the system is floating.

RE: UPS Power distribution - Selective coordination of protective devices

The most significant thing to determine is whether you want to be able to clear a fault while on inverter power, or whether you intend to rely upon the bypass supply for fault clearance. On a 40kVA unit I wouldn't expect to trip an MCB much larger than 40A Type B or 20A Type C off inverter power. The inverter typically can deliver 3x rated output current for one second and electronically limits the current to this value.

RE: UPS Power distribution - Selective coordination of protective devices

(OP)
Scotty

Thanks for your response. It really enlightened me that the short circuit level and its characteristics vary widely with inverter output or the bypass output feeding the load.

Yesterday only I came to know that the MCBs for the electronic loads have different characteristics than the MCBs used for conventional loads. Class B or Z which are suitable for Electronic /low current consuming devices. As there is no significant inrush current, the tripping time of 2 to 3 times the rated current is sufficient for such types of application.

The more I think on this, I am realizing that I know less than what I don't know!

I would appreciate if someone can share their views or way forward on the selectivity study of UPS supply distribution network. As I noticed above, the criteria for this study may to totally different. Now a days, I have noticed that the UPS sizes are getting larger and larger. The distribution networks even more complicated.

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! Already a Member? Login


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close