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


Power transformer with DC offset

Power transformer with DC offset

Power transformer with DC offset


First post here I'm new and after a quick brows through the content this seems like a good forum.

I need to test a circuits ability to withstand a ripple voltage (±7V from a 0.5R source, 50Hz - 200kHz, from MIL-STD-1275). From about 20kHz - 300kHz I want to use an amplifier (special purpose 200W 10Hz - 500kHz 2R) and couple the AC on to the DC feed via a ferrite transformer. The DC to the equipment under test (EUT) is 28V@8A. The transformer would also transform the 2R output impedance to 0.5R.

Is this achievable with a transformer? I've built a number of ferrite power inductors so have some knowledge of how they work, however, am not sure how to design for the DC offset that will be present in secondary. From what I can tell this will cause the core to saturate.. Any tips?


RE: Power transformer with DC offset

As you mention, DC saturation can become a problem.
Wouldn't it be possible to arrange a parallel path for the 20-300 kHz by using a DC block (film capacitor)?

Such a capacitor doesn't need to be huge. Not at those frequencies. A possible complication is the back-feed into the DC path.

Gunnar Englund
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Power transformer with DC offset

Thanks Skogsgurra,

I had thought of AC coupling with a cap, however the transformer was more to transform the impedance.. But that said.. a transformer to do the impedance transform then couple the AC with DC block cap. Can't believe I was complicating the issue so much! Seems this would be a suitable solution. I was planning on using a battery with a 0.5R source resistor.. So back feed shouldn't be problem.

Thanks for your input.

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!


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