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

Sizing Step Down Transformers

Sizing Step Down Transformers

Sizing Step Down Transformers

I am planning to replace a 5KV step down transformer to accommodate an additional load of approximately 800Amps @ 208V. I am confused by the term Volt Amperes and also input and output specifications. I have IEEE but it assumes an understanding of the terms. I would appreciate any information or direction.  

RE: Sizing Step Down Transformers

From the basic three phase power calculation, KVA = VOLTS X AMPERES X SQRT(3)/2.  Your 800 ampere, 208 volt additional load is 288 KVA.  The input and output voltages are to be found on the nameplate of the existing transformer.  I suggest that you engage a profewssional engineer to assist you in determining the available parameters of your electrical distribution system to determine if you can add the load to the existing distribution system.

RE: Sizing Step Down Transformers

I apologize for the incorrect formula.  The correct formula is VA = VOLTS X AMPERES X SQRT(3)/1000.

RE: Sizing Step Down Transformers

The easy non-technical answer is to think of kVA as essentially the same as kilowatts (kW), and roughly the same as horsepower.

JohnHamburger is right, hire yourself a PE, this is not rocket science but it's not a Home Depot project either.

RE: Sizing Step Down Transformers

Slight mistake in the formula:

actually, it is:




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


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