60Hz designed generator used at 50Hz

[waterbucket]

Hi all,

If i use a 60Hz designed generator at 50Hz, will that be a problem? How about keeping the same voltage/hertz ratio?

Thanks! -Frank

 

[ScottyUK]

Cooling fan efficiency will drop pretty quickly with speed, so the derating may not be linear with speed. You need to consider the alternator fan and the engine fan.

The PMG for the exciter will produce a lower output at the lower speed. This may or may not affect the operation of the AVR.

Engines for genset use are usually optimised for a specific speed, since this is well known at the time of manufacture. Things like turbochargers may not be work as well as they should. Pumps for oil and water will move less fluid at the lower speed, further compromising your cooling system. The fuel injection system may require re-mapping to suit the lower speed.

It is a question best referred to the manufacturer - many sets are capable of dual frequency operation with minor tweaks to optimise the performance. If you aren't chasing maximum available output and peak efficiency then you may well find that the set performs well enough at the lower frequency.

How big is the set, BTW?

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I don't suffer from insanity. I enjoy it...

 

[waterbucket]

thanks for the information! the rated output at 50Hz is about 60MVA and the power factor is 0.8

 

[waterbucket]

BTW, the terminal voltage at 50 Hz is about 10 kV

 

[edison123]

At 50 Hz, your generator voltage will be 5/6th of original. As Scotty said, cooling will be a problem.

At this size, talk to the manufacturer about the conversion implications.


* Basically, I would like a full-time job on part-time basis *

 

[waterbucket]

what is PMG? thanks!

how about the influence on the turbine? Is there any industrial standards/documents pertaining to this under-frequency (60Hz to 50Hz) application?

 

[waterbucket]

is PMG the permanent magnet generator?

 

[edison123]

Yes.

Is yours a hydro machine ? (going by your handle).




* Basically, I would like a full-time job on part-time basis *

 

[waterbucket]

No, it is a gas turbine having 3000rpm at 50Hz.

 

[itsmoked]

80,000 HP?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

I just wrote a detailed post regarding the conversion of diesel powered sets in the 25 KVA to 2000 KVA range.
I'm glad I checked for other posts before I posted it. It is totally irrelevant to your application.
With this size of machine and the amount of money involved, check with the manufacturer.
You are right about the Permanent Magnet Generator.
They are a nice option on smaller machines. I often specify them to mitigate voltage dips when a set is going to be starting large residential air conditioners. I service a 1.6 Mw set with a PMG.
At 3000 RPM cooling isn't nearly the problem that it may be with a 1000 RPM machine. Most of the anticipated problems can probably be resolved by de-rating a few percent, BUT check with the manufacturer.

 

[ScottyUK]

60MVA!!

Your turbine is the big problem. It is designed for 60Hz / 3600rpm. At 50Hz / 3000rpm it will behave more like a fan than a turbine. It *may* be able to sustain its own compressor load without the cranking motor assisting it, but it certainly won't deliver much meaningful output.

On an 60MVA set contact the manufacturer. My comments were based on converting a relatively small diesel set. On a large machine, my gut feeling is to buy a 50/60 rpm gearbox and interpose it between the engine and generator. This is not a simple job by any standards - seek the assistance of the manufacturer.

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I don't suffer from insanity. I enjoy it...