×
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

Open-delta connection

Open-delta connection

Open-delta connection

(OP)
I have VTs of A, b, and C phases to be connected open-delta. The ratios are 115/3 for both A & B phases and 115 for C phase. What will be the effect and what can I do?

RE: Open-delta connection

When rated primary voltages are applied, you will have 115V - 3V = 112 Volts across the BROKEN delta. What do you want to do??

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

RE: Open-delta connection

(OP)
(1)If I want to connect a Resistor across the open-delta, what will be the safe value?
(2) It was to be used for 64N protection

RE: Open-delta connection

Again, open delta is two transformers, no resistor, while broken delta is three transformers of exactly the same ratio with a resistor across the broken corner.

RE: Open-delta connection

marchar: Where in the world are you located?
In North America an open delta is as davidbeach has described; two transformers used for delivery of three phase power for generally small loads.
In Europe an open delta is three transformers in delta with one corner of the delta open. This connection is called a broken delta in north America. For this connection you must start with three transformers with equal ratios. It is not a good idea to mix 115 Volt transformers with 3 Volt transformers.

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

RE: Open-delta connection

(OP)
Thanks very much. I am in Ghana which is in the Western part of Africa.
It is not a good idea, but if it happen, what will be the effect? 115/root3 for A & B phases and 115 for C phase

RE: Open-delta connection

It won't work, for balanced system voltages you'll have a large standing voltage across the resistor instead of zero. The "right" system problem could actually push the voltage to zero. The output would be entirely worthless for protection purposes.

RE: Open-delta connection

(OP)
Thanks very much David for your appreciative contribution. My sincere regards from Ghana

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