Brushless excitation system.

[Mlmlzx]

Dear sirs,

I have studied in some manual that brushless excitation system is only for small generators that is unit lesser than 15 MW. But on this forums also many other hydrogenerators are discussed which are of higher values.

Brushless excitation are normally to be used on unit generators if the plant capacity as a whole is lesser than the whole system of the nation ie if it plays an important role in oonsideration to stability of the power grid. For major plants which play an important role, as per my knowledge, we shuud use static excitation system that too with double inverter system.

Please help me in clearing my doubts.

Please help.

 

[RRaghunath]

Brushless excitation eliminates brushgear for supplying DC current to the generator field. Thus, brushless excitation improves availability of the machine and reduces maintenance.
For the above reason, brushless excitation is popular with large machines as well.
I am aware of 500MW machines with brushless excitation.
It is true, brushless excitation adds delay to the excitation response for changes in the grid as well as during fault. But, the demerits outweigh the merits and that is the reason for its huge popularity.

 

[Gr8blu]

Mlmlzx - there are practical limits on how much energy (volts and/or amperes) a brushless excitation system can provide. Some of that is purely physics and some is related to speed. If you understand how a brushless excitation system works, you know what I mean. It is (usually) easier to provide high-volt / low-current excitation compared to the other way around. This generally means excitation for high-pole-count units are easier to supply than low-pole-count units. That being said - there is more than one means of providing brushless excitation: it could be a straight permanent magnet approach, or it could be an exciter and control wheel assembly. The control wheel version is typically able to support higher excitation requirements, at the cost of some response time as RRaghunath mentioned.

Converting energy to motion for more than half a century

 

[Mlmlzx]

i am talking about 750 rpm sets of underground powerhouse.

 

[Mlmlzx]

like for this, there will be 8 poles.