×
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

mystery voltage regulator circuit

mystery voltage regulator circuit

mystery voltage regulator circuit

(OP)
I am trying to figure out the details of a circuit that I did a thermography survey on.  I have a few partial details of a circuit and I'm trying to fill in the blanks to figure out what the circuit really would look like (*)

This is a voltage regulator circuit for a diesel generator.  It has three phase power coming in.  (possibly some other inputs), and the output is the dc current/voltage to the field circuit of the diesel genrator.

There were 6 power diodes arranged in a 3-phase full bridge rectifier arrangement.  Three diodes were associated with the negative dc output and three diodes were associated with the positive dc output.   

Here's what puzzles me.  We measured the dc current on positive and negative ouptut leads and they are the same (as expected by KCL).  We measured the dc current on the 6 diodes and found that the three diodes associated with the negative output bus were carrying approx twice the current of the three diodes associated with the positive output bus.

Obviously that wouldn't be expected for a simple full bridge rectifier.  I was told this is a little more complicated:.  In addition to the diodes, there are some SCR's in the circuit for regulation purposes, but I'm not sure exactly where.  I was told perhaps they shunt a portion of the current to regulate the output.  And this feature explains why the negative diodes were carrying higher currents.

I flipped through my textbooks and couldn't find any voltage regulating circuit (or current regulating circuit) that includes a full bridge rectifier (diodes) with additional regulation provided by SCR's.  Is anyone familiar with that type of circuit ?

*  PS - If I had a readily-available circuit diagram or a precise desription of the circuit, I wouldn't be asking this question.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: mystery voltage regulator circuit

Are you gonna fess up the brand/model at least?  I mean someone may have the exact schematic laying around.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: mystery voltage regulator circuit

Check those six diodes in the bridge.  Three of them might be your missing SCR's.  Sometimes the gate terminals aren't really obvious.

old field guy

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