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vimalkumar
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Join Date: Jan 2010
Location: mumbai
Posts: 13

Turbine Speeds

01/13/2010 9:01 AM

why turbine speed is maintained at3000 rpm in india ?
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535143
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United Kingdom - Member - New Member

Join Date: Jan 2010
Posts: 11
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#1

Re: Turpine speed issue

01/13/2010 12:05 PM

YOUR ANSWER LIES IN THE FORMULA N=120F/P WHERE N(SPEED), F(FREQUENCY), AND P(# OF POLES) IN INDIA 50c/s frequency is required thats why 3000rpm speed is maintained. F=NP/120 IF P=2, N=3000 THEN F=50Htz
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Anonymous Poster
#2

Re: Turbine Speeds

01/14/2010 12:46 AM

Just a little bit of correction in the question.

It is the alternator whose sped is maintained at 3000RPM (in India and other 50Hz countries) and 3600RPM (for 60Hz countriies)

As mentioned above 3000RPM corresponds to 2 pole 50Hz machine.

You try to increase the RPM to maximum to get maximum power for same volume (and hence the materials of construction) and land up in minimum number of pole pairs (1 pole pair or 2 pole machine)

You may like to have a look in any HP 3000 RPM motor and the same HP say 1000RPM or 750RPM motor and the thing will be clear.

There are several turbines with much higher speed (especially the Gas turbines) - however the speed at the alternator is again reduced to 3000 RPM through gear boxes. The GT is a bit complex and are optimised for the highest speed, and trying to maintain the 3000RPM its efiiciency will drastically drop.

The ST (steam turbines), or even Diesel Engines are designed for the 3000 RPM without having to compromise on this aspect.
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drhead
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Join Date: Jan 2010
Location: Austin Texas
Posts: 1
#3
In reply to #2

Re: Turbine Speeds

01/16/2010 12:46 PM

Just a quick question from someone who is new here, if you were spinning a generator instead of an alternator, would you have the same speed restrictions. I understand that you would have to convert from DC to AC, but once again, would you have the same speed restrictions? Also, is there that big of a loss or cost concern to generate DC and convert it to AC at the site of generation?
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Jerry New Hampshire
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Join Date: Mar 2009
Location: Northeast corner of the sphere
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#4
In reply to #3

Re: Turbine Speeds

01/17/2010 7:49 PM

From a guy who has owned cars that ran 6 volt generators, the faster you spin a generator, the more voltage you produce, as measured with my trusty multi-meter. There may have been factors not readily apparent like volt/amp/watt relationships, but I would get more volts as the speed came up.

In the Edison / Westinghouse battle for supremacy, George Westinghouse won out with his AC alternators because it could be easily transformed and broadcast with minimal losses. The only places I have seen AC/DC dynamos are old machine shops where the machines run with DC motors for simpler speed controls.

To the topic at hand, I have seen 1,800 and 1,200 RPM steam turbine generating set-ups for 60 cycle power.

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