weak link between gearbox and PM generator

[DHambley]

I'm curious. For wind generators is it typical to incorporate a weak link on the shaft between the gearbox and the generator. This would be for the possibility of a stator winding fault. The EMF of a PMG will create hundreds of amperes of current, only limited by the impedance of the stator winindgs, possibly causing a fire hazard. The torque created by this fault current would shear the weak link.

Or, on the other hand, are these generators so reliable that my concern is not an issue at all?

thanks

 

[Warpspeed]

Why not just fit a fuse or a circuit breaker to the winding ?

Any excessive fault current will then open the circuit and do electrically what you plan to do mechanically.

 

[DHambley]

My work has been with generators in aerospace. Internal winding-to-winding fault is a concern in these applications. An external fuse will not protect in this case. This is why field weakening is desinged into these systems but, with a PM machine this can't be done. Thus, my curiosity of how this is addressed for wind generators.

 

[OperaHouse]

I would be more concerned about a free wheeling blade than a generator in flames. I would almost assume these have an auto brake in case a load is lost.

 

[sms]

Here is what happens when it doesn't work....

http://www.liveleak.com/view?i=cdd_1203701257

"Why don't you knock it off with them negative waves? Why don't you dig how beautiful it is out here? Why don't you say something righteous and hopeful for a change?" Oddball, "Kelly's Heros" 1970

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[jmw]

Youtube has two views of this,

http://www.theregister.co.uk/2008/02/27/disintegrating_turbine/

but a version at

http://gizmodo.com/360117/exploding-wind-turbine-video-is-destruction-delicious

has slomo

JMW

http://www.ViscoAnalyser.com

 

[BrianOnkst]

The "weak link" is usually the flexible coupling that is installed between the gearbox and generator. Newer turbines may also incorporate a torque limiter that is built into the coupling, which allows a slight "slip" when very high loads are encountered (perhaps for 100ms). The torque limiter reacts instantly to the brief overload, protecting the entire drivetrain. When the event is over, the torque limiter resumes normal driving function.