we have manufactured a small 75 kw steam turbine and was commissioned in a site. we used an induction generator for power generation. we used to keep the turbine speed at about 1500 rpm at 50hz and then closed the breaker and synchronized with grid, but later on twice the nuts got cut in the low speed coupling connected between gear box and generator. and later we changed the nuts and then then the coupling got damaged. this time we changed the coupling again and the same happened. then we reduced the diameter of the coupling according to one consultant and again the same happened. then again we reduced the distance and the same happened.

then after the analysis turbine experts concluded that the problem is with electrical part. what can be the reason, and what is the solution. we have the reverse power relay as well as over voltage and under voltage relay in the control system. whether it is because of our wrong method of synchronization? or any other problems with slip?
somebody please help me in this.

my email is : shaibykoshy [at] gmail.com
my phone no:+919880467640

 

Koshy... Apparently during run-up of the STG driver, there is sufficient residual magnetic flux in the motor to produce a terminal voltage.

Thus, if you close the breaker out-of-sync, the resultant torque produced will cause the coupling failure (not an unusual happenstance.)

This then leads to the question, "How are you syncronizing the IndGen to the source of supply?" Using speed (or Hz) alone as the synchronizing criterion you are asking for disaster!

Regards, Phil Corso (cepsicon [at] aol.com

 

Dear sir,

if sync is to be done not only with speed (Hz) what all things need to be taken care kindly give me a detailed explanation and a solution which can be implemented

regards
Shaiby Koshy

 

Koshy,

I have additional questions. Contact me off-list.

Regards,
Phil Corso (cepsicon [at]aol.com