GE Gas turbine Frame 6 SFC

Sikandar7641,

There are GE-design Frame 6B heavy duty gas turbines, and GE-design Frame 6FA heavy duty gas turbines. So, a "Frame 6" is not like every other "Frame 6."

I have only ever seen LCIs (Load Commutated Inverters, or SFC (Static Frequency Converters)) used on Frame 6FA turbines.

The topic and operation of LCIs/SFCs has been covered previously on control.com. There is a Search field at the top of every control.com webpage (desktop version) at the far-right of the Menu bar. It can be used to find previous threads and other information.

In a nutshell, the LCI/SFC is used to convert the generator to a motor for starting the gas turbine (Frame 6FA). There are many switches and interlocks which must be properly sequenced to temporarily convert the generator to a motor, and then the LCI/SFC applies a variable frequency AC to the stator windings (while the exciter system applies DC to the generator rotor) to accelerate the turbine shaft for purging, firing, warm-up and acceleration to near rated speed--at which point the LCI/SFC is shut down/disconnected from the generator and the switches/interlocks are returned to the "generator" position and then the generator is synchronized to the grid with other generators and their prime movers.

LCIs/SFCs use semiconductors to chop incoming high-voltage AC into variable frequency AC to use to accelerate the turbine shaft. This prevents having to use another separate electric motor for starting the turbine (by temporarily converting the generator to a motor during starting).

If you need more information than this, and after reading previous threads, please be more specific about your want.
 
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Sikandar7641

Thanks for your reply...

as i m facing problem with my SFC....
Time out excitation alarm pops up. Can you please guide what could be the possible reasons?
 
Sorry; I'm not familiar with that alarm. It sounds, though, like something is preventing the exciter from starting. Are there exciter alarms present before trying to start the turbine? Do exciter alarms pop up after a turbine START is initiated? That's where it's suggested to start looking. These kinds of alarms don't usually happen by themselves without other related alarms either not being resolved before the START or occurring shortly after the START is initiated. This includes Diagnostic Alarms.

You haven't said who the manufacturer of the SFC /LCI is.
 
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Sikandar7641

> You haven't said who the manufacturer of the SFC /LCI is.

Converteam is the manufacturer.

during start up when SFC sends a request to excitation system for exciting, some time during excitation, this alarm pops up "time out excitation." it looks like either exciting system is not responding in specified time given in the logic.
 
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