60 Hz Generator at 50 Hz

[astroid]

A turbo generator rated for 60 hz is required to generate at 50 hz. Assuming all utility eqipment are changed to 50 hz, and monitoring, metering and protection settings are availible for 50 hz, will changing governer setting to slower rpm and adjusting excitation be able to deliver rated power at 50 hz.

 

[Skogsgurra]

You will need more excitation to get full voltage at 50 Hz. Thermally, the same current as before is available*. So, if you can increase excitation (may not be possible because you are may already be into the non-linear part of the excitation curve), you should be able to get same power at 50 Hz. But, as I said, it may also not be possible. The generator will not be able to deliver vars like before (because more excitation is needed to produce voltage).

*Not always true. Cooling is less effective at lower speed.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

For a diesel set, 20 KVA to about 2000 KVA it is usually possible. Many standard sets are configurable for either 50 Hz or 60 Hz.
Speed: The governor is adjusted to the new speed.
Voltage/excitation: The AVR is adjusted for the new voltage. 50 Hz voltages are typically less than the corresponding 60 Hz voltages. 400 V at 5 Hz and 480 V at 60 Hz comes to mind. The implication is that the V/Hz ratio doesn't change that much with the conversion and saturation is not an issue.
Under Frequency Roll Off. (UFRO) Change the jumper on the AVR from the 60 Hz position to the 50 Hz position.
The maximum current will be the same but the max KVA and max kW will drop at 50 Hz due to the lower voltages.
BUT, this is a diesel set.
I understand that torque drops off rapidly with an aero derivative turbo set. Stand by for the folks with turbo experience to weigh in on the efficiency of a turbo at reduced speed.

Bill
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"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Re-draw the capability chart for 50Hz operation. You might be able to wring the same power out of it, at the expense of having little or no reactive capability. Bear in mind that there are a lot of parameters which will change, e.g. the performance of the exciter, the capability of the shaft-mounted cooling fans to move air through the stator, and so on.

Overall I would say probably not, at least not without some re-engineering which will need support from the OEM.


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If we learn from our mistakes I'm getting a great education!

 

[Masbibe]

Just to mention that you will need 20% more torque than before on turbine, shafts and generator to achieve rated power. If this is OK then just concentrate on electrical problems that guys said above.

Milovan Milosevic

 

[edison123]

You'll need to derate the machine and the rated voltage to 5/6th. I doubt 3600 RPM steam turbine would work that well at 3000 RPM. There could also be critical speed issues.

Muthu

http://www.edison.co.in

 

[rmw]

Assuming that driver issues are not part of the OP's question, generator issues would include:

If it is an air cooled machine, it will not pass as much cooling air through the core so that will affect the ultimate performance rating capability. Same principal would apply with a TEWAC or H2 cooled machine. Less rotor speed produces less cooling medium flow in the generator internals. That is an integral part of the derate picture already presented.

If the machine was not designed day one to be convertable from one frequency to another, I would check with the OEM to see what the limitations would be. The comment about shaft criticals is important to check out.

If your turbine change to accomodate the frequency change involves a change in direction of rotation, then you will have to reverse your rotor fans and remember if it has a rotating exciter that there may be a fan there too. With some manufacturers, that fan cannot be reversed but has to be replaced.

Modern seroderivitave packages are designed for 50/60 hz with corresponding ratings. Some of the older packages, however were designed for a specific frequency. Much of what you can/can't do if that is what you have depends on whether or not it is a hot end drive or a cold end drive.

rmw

 

[burnt2x]

What edison123 said could be a big problem. My personal experience with a single-shaft GT operated at 60Hz exhibited a second-stage stage critical speed at around 3005 rpm. We have to program a quick ramp-up when nearing that speed to do away with high vibration amplitude. But not all machines are done the same though, mine could have been an exception.

 

[waross]

What are your voltages at 60 Hz and 50 Hz. What size machine do you have. For example, rotor cooling is not often an issue on a 250 kW set, but is an important consideration on a 20 MW set. The conversion of a 60 Hz set to 50 Hz often involves dropping the voltage from 480 V to 400 V. As a result, saturation and/or excitation is not an issue. However if you intend to generate the same voltage at 50 Hz as at 60 Hz you may have serious issues.

Bill
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"Why not the best?"
Jimmy Carter

 

[nawao]

You will have issues with water cooled engine (less water speed as well as air speed circulation). Possibly overheating will occur before reaching rated power.

 

[waross]

Not so for most sets manufactured by the largest liquid cooled diesel gen-set manufacturers.
Virtually all the major liquid cooled diesel set makers use the same sets for 50 Hz and 60 Hz. The engines produce virtually the same torque at 1500 RPM as at 1800 RPM with no cooling issues, with either the coolant loop or the air cooling systems.
But this is a turbo question.

Bill
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"Why not the best?"
Jimmy Carter

 

[burnt2x]

Quick thinking Bill. I almost forgot this one's a turbo question! The OP should be able to point out which scenario is his.

 

[nawao]

Cat sizes their generatrs differently between 60 and 50Hz.
There are arrangmets with different radiators, fans and driving pulleys. Agreed thas is also a turbo question.

 

[waross]

I apologize nawao. Time is creeping up on me. When I was spec'ing and installing a lot of Gen-Sets, 10-20 years ago, all of my suppliers used sets suitable for 50Hz or 60 Hz.
I just spent some time going over a selection of current specs and I find that more and more sets are frequency specific. There are still a lot of sets suitable for use at either 50 Hz or 60 Hz. More than half of the sets on the specs I just looked at are suitable for 50/60 Hz.
As the sets get larger there is a trend towards frequency specific sets. Some use a mechanical governor at 50 Hz and an electronic governor at 60 Hz. The mechanical governors won't go to 60 Hz, but the electronic governors are suitable for 50 Hz or 60 Hz.
Thanks for the heads up.

Bill
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"Why not the best?"
Jimmy Carter