electricpete
Electrical
- May 4, 2001
- 16,774
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.
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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.