# Special Power Current Transformer

Discussion in 'General Electronics Chat' started by n1mr0d, Apr 19, 2006.

1. ### n1mr0d Thread Starter New Member

Apr 7, 2006
5
0
Hi, i am currently analyzing a compound-type static exciter, which utilizes a potential transformerand a power current transformer (pictured below) . This current transformer is connected to the neutral side of the generator, and kicks in when large currents are flowing. Not much is known about this thing.

It has the following nameplate (located on the back!):

H 16-1-1
16-1-1
Z 2-1
2-1 Y3
(Y=pri/Z,H=sec)

Which actually makes some sense, because it is a multi-tapped transformer, specially tuned to the generator.

From how wires are connected we can derive the following winding configuration (viewed from the side of the transformer):

H  Z Y Z  H
18 3 3 3 18

The Z and H windings are put is series in a special way, which seems to derive the max amplitude.

I would like to derive the pri/sec phase and amplitude characteristics of the voltage and current (cos phi=0.8).

2. ### kubeek AAC Fanatic!

Sep 20, 2005
4,691
806
Will you please tell me generally what is this whole device (static exciter) for?

3. ### n1mr0d Thread Starter New Member

Apr 7, 2006
5
0
This transformer is only a part of the static exciter. An exciter is used for providing field current, so a voltage is induced in the stator windings of a generator.

4. ### kubeek AAC Fanatic!

Sep 20, 2005
4,691
806
I don´t understand the 18 3 3 3 18 part. What do the numbers mean?
I thought Z part is a three-phase transformer with 16 to 1 to 16 ratios for sec-prim-sec on one phase. The same way is the H part connected 2 to 1 to 2.
Are the windings on one magnetic core or they are separated? I don´t see it from the picture.
What does the "neutral side of the generator" mean? Is it the part where L1 L2 and L3 are connected together?

5. ### n1mr0d Thread Starter New Member

Apr 7, 2006
5
0
If you have a tapped transformer/coil each tap is assigned a number of coils which you can add together. The H-side has 3 taps, so if you use the last tap you get 16+1+1= 18 windings. Same with Z-side: 2+1-3. So 18-3-3-3-18.

Also i assume it is has laminated iron core, otherwise you get very bad flux linkage.

PS: The neutral side is indeed where the star-point is located

6. ### kubeek AAC Fanatic!

Sep 20, 2005
4,691
806
I still don´t get why you add 16+1+1 when 16 is primary and 1+1 are paralleled secondaries, but that´s not the main point.

Can you take the device temporarily apart to measure inductances in the transformer? This would be much more useful for some simulation.

How big are the SCRs in the control part of the circuit? What is SCR3 connected to?
Is it some curcuit which prevents from overvoltage on the stator field?

Personally I think that when the generator gets more load, the current throug the transformer raises and adds to the voltage from the main line on the stator field.

7. ### n1mr0d Thread Starter New Member

Apr 7, 2006
5
0
Y is the primary side of the tranformer, connected to the terminals of the generator. Z & H are the secondaries. The both H windings on both sides of the are put in parallel; same for the Z windings.

SCR3 is located inside the Automatic Voltage Regulator and phase-fires SCR2, so every half-cycle some power is shunted off.

8. ### kubeek AAC Fanatic!

Sep 20, 2005
4,691
806
So can you take the transformer apart and measure the inductnaces?
Then if you had some theoretical model of such genereator, you would be able to simulate it.

And by the way, what is the main problem that makes you analyze this whole device?