Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Transformer Marking
Name: John M.
Status: Other
Age: Old
Location: N/A
Country: N/A
Date: 2001

I have a transformer that does not tell what type it is all it has is a long line with three short dashes under it.Can you tell me if it is AC or DC by this symbol.Thank you.


I am not an engineer, but I have been around a lot of transformers. I am not aware of a DC transformer. The changing flux of AC in the primary is required to induce a current in the secondary.

The closest thing to a DC transformer is a saturated core reactor. It uses a DC current to increase the density of the magnetic flux in the core thereby decreasing the loses to the AC signal impressed over the DC signal. A rather unusual situation and likely not yours.

I do not know your symbol, but it might be the electrical symbol for a transformer with a portion missing.

Larry Krengel

Click here to return to the Engineering Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory