IN MY POWER PLANT OPERATE 2 GE MARK V FRAME 9 DLN2. IN ONE OF THEM DURING NORMAL OPERATION CRANK MOTOR ROTATE. IT SHOULD BE STOP IN THIS CASE. I AM NOT IN MY COMPANY NOW. THANK YOU IN ADVANCE

 

If the post is understood correctly, the unit is a GE-design heavy duty Frame 9 gas turbine, with DLN-2 combustors, with a continuously running cranking motor while the unit is running. (But the post isn't really clear.)

There are Frame 9<b>Es</b> and Frame 9<b>Fs</b> (and FAs and FBs). Most Frame 9Es have cranking (starting) motors that are used to start the unit by transmitting torque through a variable output torque converter. However, most of these machines, when equipped with DLN combustors, have DLN-I and not DLN-2. But, hey, things change!

If you're saying the cranking motor (88CR) is running when the turbine is running at rated speed, then there's either a problem with the output from the Speedtronic that's driving the cranking motor starter, or there's a problem with the cranking motor starter's control power circuit that is not opening the contactor for the cranking motor to stop it.

If you're saying the cranking motor is running the turbine is not running then the same is true--either the Speedtronic has not told the motor to stop for some reason (not likely), or the Speedtronic relay output contacts have welded themselves shut, or the motor's contactor has not been opened by the motor starter's control circuit.

Most of these cranking motors are high-voltage (4160 VAC or thereabouts) induction motors and have across-the-line (full voltage) starters. They usually have some kind of manual "stop" push-button on the outside of the starter's compartment/cubicle which can be used as an emergency stop push-button to open the contactor and stop the motor.

If not, there is usually a manual device for isolating the motor starter/contactor from the mains supply. <b>I would NOT recommend opening this while there is current flowing through the starter contactor!!!</b> But, somehow the motor should be stopped.

But something is definitely amiss if the post is understood correctly.

If you're referring to a "cooldown" or "turning gear" motor for a Frame 9F (or FA or FB) running when the turbine is running, it would be the same thing--either the Speedtronic hasn't told the motor to stop for some reason (not likely, but the relay output contacts may have welded themselves shut) or the motor starter contactor or control power circuit is failed in some way.

Most F-class units use the generator as a starting motor (and for "cranking" such as during testing or off-line water washing) and they wouldn't be "running" when the unit was producing power (at least they wouldn't be running as motors!!!).

 

if i remember correctly, long time ago we have a problem in our site where the 88CR keep on spinning during normal loading. no power is supplied to the cranking motor. the problem was with the clutch/torque converter because it was not fully disengaged. the prime mover is turning the cranking motor. hope this helps.

 

Well, I hadn't considered this possibility. One would hope the originator would be able to tell if the cranking motor was being powered by its AC supply or not....

Most of these Frame 9E electric starting motors are directly coupled to the input shaft of the torque converter; that is, no jaw clutch or clutch of any kind between the cranking motor and the torque converter. If the torque converter input shaft was being driven by the output shaft of the torque converter via the load coupling from the turbine shaft, then one would think something was amiss with the torque converter, or the solenoid(s) used to pressurize the torque converter.

Under normal staring conditions, the torque converter is depressurized when the turbine shaft speed reaches 60% speed, and the cranking motor continues to run for a couple of minutes or so just to cool the cranking motor windings and rotor using the air circulated by the rotor fans. Remember, under normal starting conditions the cranking motor is running at 150-160% of rated current/torque and so it's run unloaded for a few minutes after the torque converter is "unloaded" by depressurizing it to help with the cooldown of the motor. Once the cranking motor cooldown timer expires, the cranking motor starter is opened and the cranking motor decelerates to zero speed.

It's conceivable that if 20TU-1 did not "release" or was not de-energized while the turbine was at rated speed (or above 60% of rated speed) to de-pressurize the torque converter that somehow the output shaft of the torque converter could cause the input shaft to rotate and spin the cranking motor rotor.

Some torque converters have a second solenoid, 20TU-2, that is used during cooldown operation. It's also possible that it might (unlikely) cause a similar "reversal" if it didn't release or wasn't de-energized while the turbine was running.

So, 20TU-1 is the normal way the torque converter is used as a "clutch", by pressurizing the torque converter when energized and de-pressurizing the torque converter when de-energized. It's conceivable if the torque converter wasn't being de-pressurized (either because the solenoid wasn't de-energize) or wasn't mechanically operating to de-pressurize the torque converter that it might cause the torque converter to spin the input shaft and make it appear as though the cranking motor was running.