×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

How many additional load available for existing transformer ?
2

How many additional load available for existing transformer ?

How many additional load available for existing transformer ?

(OP)
We have a unit new 75kVA dry transformer on site now. I would like to know how many of the existing transformers can handle more load in the future. After checking the existing demand load, around 50kVA was used up to date. The name plates say that low-temperature rise of 80 C and the insulation class was 220 C. Can we add a new load up to the 25kVA? Thanks for any input in advance !!

RE: How many additional load available for existing transformer ?

Mr. james64 (Electrical)(OP)10 Jul 23 00:42
"....We have a unit new 75kVA dry transformer on site now. I would like to know how many of the existing transformers can handle more load in the future. After checking the existing demand load, around 50kVA was used up to date....."
1. What is your existing transformer kVA rating? If it is say 50kVA, you are at full load. You can not add more load unless the existing pf is low. You can add some load by improving the pf.
2. If your existing transformer is say 75kVA, you can add an additional of 25kVA to you existing load of 50kVA.
3. Your new 75kVA transformer can take up another load up to 75kVA, irrespective of your existing loads.
Che Kuan Yau (Singapore)

RE: How many additional load available for existing transformer ?

Two ways to go:
1. Do the demand calculations according to code. You may not be able to add load based on these calculations.
2. If it can be shown that the existing load, etc.
There are two ways to show to the AHJ that the existing load is low enough that more load may be added.
a} Recording demand meters on the existing loads for a time acceptable to the AHJ.
This may be 6 to 12 months.
b) If this is a main service transformer, ask the accounts payable department for copies of the last two years of power bills.
Look at the maximum demand each month for the last two years. The AHJ may allow you to ignore the highest demand as an outlier, it depends.
Note: when adding KVAs, PF matters. If the added load is at a significantly different power factor than the average PF of the existing loads, the actual combined KVA may be less than the simple sum of the existing and added KVAs.
That said, simple addition is always safe.
Don't worry about the PFs.
But, If the measured KVA after the addition of new loads is slightly less than the calculated KVA, this is probably why.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

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

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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