10 MW Steam Turbine Generator - Conversion from 60 to 50 Hz

Have you consulted the turbine & generator set manufacturer?

Yes, it can be done. The most economical solution is to convert the generator to 50 Hz. The turbine will not require modification.

If speed of turbine is changed its output too will change,there was a thread on this.

Some electrical equipment has a little switch on the side that changes it from 50Hz to 60Hz. Very handy, but you won't have that on this electrical equipment.

Have you gone back to the manufacturer and discussed this with them (not the switch the 60Hz operation)? They built it after all they should be able to offer some advice?

Look up the following site and commission as per option 1:

http://www.dieselserviceandsupply.com/Generator_Frequency_Conversion.aspx

This will entail changing:

1) RPM feedback control parameters of the turbine

2) Field control of the alternator

That's it nothing more.

I am assuming that this is a steam turbine driven Generator. Please DO NOT ATTEMPT. This is not a job to be attempted by traders. The generator is 30% electrical and 70% mechanical. Lot of electrical and mechanical engineering goes into the design of cylindrical generator. The critical speed of the generator, turbine as well as combined critical speed are kept away from running speed. By changing the speed for changing 60Hz to 50Hz may bring the running speed and critical speed very near and may cause heavy vibrations. Similarly the last stage of LP turbine blades are also tuned to keep their natural frequency away from running frequency. Change of running speed may also cause those blades to vibrate excessively and may result in catastrophic failure. These are few of numerous considerations, I have tried to explain. So let the job be done by regular manufacturer.

Hi

I think you definitely need some technical assistance. I dont believe critical speeds on the generator will be your problem, at 10MW its likely to be a salient pole machine and will run ok at 1500rpm. There are other considerations, voltage for instance. What is it nw and what do you want? The reduction in speed also means a reduction in output, so you will only achieve 8MW from the generator. If its high voltage, there are CT's and VTs to consider as well, plus excitation etc. Its certainly not plug and play, and there is unfortunately no switch on the side.

It can be done and has been done, but just needs some engineering.

I think it is doable.

1) Turbine control system and generator AVR need reconfiguration. The new speed will be 3000 rpm (if it is 2-pole generator and 1500rpm if it is 4-pole generator) instead of 3600rpm. Correspondingly, the generator rated voltage will be less at 50Hz by about 20%.

2) The output of the turbine-generator also will be lower and hence will have to be re-rated.

Many of the T-G manufacturers make the equipment suitable for both 50Hz and 60Hz systems and I think there will not be much of design issues.

If a turbine & alternator designed for 3600rpm runs at 3000rpm,the mechanical forces created won't match the original designed values & also cooling air of alternator will be less.

I agree with you, if you ever operate turbine, each speed has different machine characteristic. This also related with process. Slower turbine rotation is also has greater vibration

Dear friend,

Change the Gear Box with suitable Ratio, to reduce the speed of Alternator. Provide external air cooling arrangement to take care of Alternator Winding Cooling.

DHAYANANDHAN.S