self excited induction motor

[nandarora]

can anyone give me a detailed description of working of isolated induction generator or self excited induction generator

it has been mentioned about it in the following link in the last paragraph but no details are given

http://electricalstudy.net/lesson/poly-phase-induction-generator-or-asynchronous-generator-2/

can anyone refer me a link or book from where i can study about it in detail.

 

[waross]

A motor has some residual magnetism. When the motor is rotated by an external force the residual magnetism will generate a small voltage. Capacitors may be used so that this small voltage will cause a current to circulate between the motor windings and the capacitors. This aids the buildup of the field strength and voltage until the core approaches saturation.
Some motors do not retain enough residual magnetism and will not "boot strap" themselves as an induction generator.
A purpose built induction generator will be designed for adequate residual magnetism.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Remember that in the first figure in the link that you posted, the part of the curve of interest is the small part between A,B and C.
Further, the safe operating range is from a to B and a similar distance below the line in the generating quadrant.
Another point: That figure is a little misleading. It shows the operating point or torque at about twice the starting torque.
According to the Cowern papers [

http://www.baldor.com/Shared/manuals/PR2525.pdf

page 7] the operating point or torque for a design "B" motor (one of the most common motor types in North America) is about 2/3 of the starting torque. The safe operating range of many motors is much less than is implied by your link.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[nandarora]

Thanks for your reply.

Can you give me a link from where I can study the operation of islanded generator in more detail.
I wish to understand how frequency is different for different speed in case of islanded generator unlike the case of the generator which is connected to the grid.
Is there any link or book available for more details?

 

[waross]

Search this site for generator posts. The characteristics of grid connected and islanded generators have been discussed several times.

Bill
--------------------
"Why not the best?"
Jimmy Carter