# Static Exciter Analysis

#### n1mr0d

Joined Apr 7, 2006
5
Hi,

At my work we got a generator whose field fed by a static exciter, which i was assigned to analyse. The exciter seems to be of the 'current boost' type, a special current transformer is included in the circuit to boost the field during faults or large inrush currents.

Three transformers are used in the circuit, a power potential transformer, a power current transformer and a phase shifting transformer. The PCT is unlike any other CT i have seen; for each phase it seems to consist of a thick primary winding sandwiched by 2 secondary windings. I don't know anything about the ratio's or anything. The phase shifting transformer is connected in series with a reactor, which i don't know the purpose of.

The six phases are connected to a 12-pulse rectifier bridge for a low ripple and is put in the field. Left of the rectifier bridge are two thyristors for regulation purposes. The lowest thyristor is commutated by the middle phase off U2.

Can someone give a analysis of the phase shift tranformer part in conjunction with the current transformer, and the thyristor part of the circuit?

Exciter schematic

This is the special current transformer.

#### kubeek

Joined Sep 20, 2005
5,757
Originally posted by n1mr0d@Apr 7 2006, 11:33 AM
Hi,

At my work we got a generator whose field fed by a static exciter, which i was assigned to analyse. The exciter seems to be of the 'current boost' type, a special current transformer is included in the circuit to boost the field during faults or large inrush currents.

Three transformers are used in the circuit, a power potential transformer, a power current transformer and a phase shifting transformer. The PCT is unlike any other CT i have seen; for each phase it seems to consist of a thick primary winding sandwiched by 2 secondary windings. I don't know anything about the ratio's or anything. The phase shifting transformer is connected in series with a reactor, which i don't know the purpose of.

The six phases are connected to a 12-pulse rectifier bridge for a low ripple and is put in the field. Left of the rectifier bridge are two thyristors for regulation purposes. The lowest thyristor is commutated by the middle phase off U2.

Can someone give a analysis of the phase shift tranformer part in conjunction with the current transformer, and the thyristor part of the circuit?
Exciter schematic

[post=15930]Quoted post[/post]​
Do you know something more about it? I stopped on the first sentence.
This whole thing is the static exciter? Than what is the generator? Do you know the purpose of the whole thing? where is some input and output?

Explain it more thorougly and maybe then someone will be able to answer your questions...

#### Erin G.

Joined Mar 3, 2005
167
The PCT, as you call it, apears (by the drawing) to be an isolation x-former. It separates the line side feeding the the PPT from the actual power source. This may sound like an oxy-moron because the "source" in question is actually part of the output of the generator. However, when load is placed on the generator, the line voltage to the input of the excitor become susceptable to surges and other noise tranisents induced on / by the loads. Note that the excitor itself beacome a load as well.

The line reactors are inductors that act as nothing more than noise reducers. They work in tandem with, and increase the noise reduction provided by, the isolation x-former. These reactors are very common in any static (AC to DC) conversion circuits with relatively high volatge / heavy load conditions.

#### kubeek

Joined Sep 20, 2005
5,757
Originally posted by Erin G.@Apr 12 2006, 02:21 AM
The PCT, as you call it, apears (by the drawing) to be an isolation x-former. It separates the line side feeding the the PPT from the actual power source. This may sound like an oxy-moron because the "source" in question is actually part of the output of the generator. However, when load is placed on the generator, the line voltage to the input of the excitor become susceptable to surges and other noise tranisents induced on / by the loads. Note that the excitor itself beacome a load as well.

The line reactors are inductors that act as nothing more than noise reducers. They work in tandem with, and increase the noise reduction provided by, the isolation x-former. These reactors are very common in any static (AC to DC) conversion circuits with relatively high volatge / heavy load conditions.
[post=16113]Quoted post[/post]​
Could you please explain it a bit more? I stil don´t understand anything about it. What is it good for?
I assume it is some kind of power source (?) but where does it take some energy?