25 HZ frequency

Much less efficient way to transfer energy for household goods that use a step up or down transformer. You need bigger transformers to do the same things as you would with 60Hz. That is why switching power supplies are so efficient. They generate frequencies well into the kilohertz and have very tiny transformers. Open up your PC power supply sometime.

The efficiency of switchers lies in their pulsed operation, not their magnetics. But yes, a lower frequency signal needs a larger transformer. Switchers these days operate in the 100's of KHz to a few MHz.

you don't know what you're talking about. Hz is about the timing of the wave, and current is about the the amount needed withing that time, so that 25 hz has an output of half 50 Hz.

You don't know jack about Transforming either. you guys seem to be long on tails, and short on actual facts... the both of you are just jacks

re 25 Hz frequency by guest is is part right, the max speed of 2 pole ac motor would be 1500 rpm vs 3000 rpm for 50 Hz. the amount of power would be the same, why would an arc furnace notice any difference between D.C. to 60 Hz? answers 1 & 2 are right in a sense that you need less iron in 60 Hz motor or transformer then 25 Hz

perry

the max limit for 2 pole @ 50 hz is 3000 rpm.

"...to 60 Hz?" what? are you trying to say that you have answers when you can't even provide simple power output calculations? there's a 10% power difference assuming that volage and current size remain even.

"...you need less iron in 60 Hz motor or transformer then 25 Hz" OH!?, how many transformers have you built? how does you calculate the amount of turns needed to balance current output with the voltage size?

And Damn you Jason, should have said nothing to you!!!!!!

that should read 20% power difference

They probably just replaced the transformers for the furnaces. Most likely they were ancient, so replacing them with 60Hz transformers which would be a lot more efficient, would be paid for by the reduction of their energy bill over time. On something like an arc furnace, the payback could be very short.

Some of the big pumps that were in use in New Orleans before Katrina hit were still 25Hz. Most of those were the oldest ones and were flooded, so now the replacements will be 60Hz. Technically I suppose, all of us here in the US are paying for that!

Re: New Orleans Pumps, 25 Hz. The Corps told me 25 Hz was more efficient for large motor loads, so that is why Mr. Woods utilised 25 Hz a hundred years ago, and they built a 25 Hz power plant just to feed those pumps, still in existence I think. I'm no EE so I just swallowed the story and went on designing diesel powered vertical mixed flow pumps (about 18 feet diameter [5.5 m]) for a Value Engineering presentation to the Corps each with a capacity of 15,000 US gallons per second (or 53 m³/s or 31 million bbls/d or 2400 cfs) each pump driven by a 250 ton 14,500 Hp (10.8 MW) automatic start and self contained, no outside power needed at all, not even control power. About 15 units are required to pump out the various collection points. This overall concept has been adopted and should be part of the super stations on the drawing board now, with smaller engines and multiple pumps; maybe 30-50 units. And no . . . I didn't have anything to do with the existing temporary pumps that are reported as having tons of problems. I did offer to fix them, however. I heard they might retain some of the 25 Hz pumps.

Please re-check Post 27 in:

http://cr4.globalspec.com/thread/10129/50-Hz-and-60-Hz-Pros-Cons-and-National-Standards
appended below

1. There are some more Frequencies used certain Countries eg 45Hz2. 400Hz used by Aviation internationally.The reason is the weight of Power-Units of avianoic-equipment.
Note: This alone reason saves a lot of Copper & Core-material of Wound Components like transformers, motors etc. But it is impossible for a community or country to go to the other sysem. It involves un-immaginanable financial involvement & years of ..
I remember when due to Hydro-electric developements in my country a few towns using DC supply were converted to AC in almost 5/6 years only due to ceiling-fans & a few Saw-Machines in Wood cutting small setups. It was 1950s.
3. At higher frequency the lighting-flicker effect is lower than the lower freqs.4. Decision to adopt 50, 60 or else & voltage for Electrical-Power was decided by each county's Technocrats at that time and what-ever was decided cannot be reverted to the other just by discussions but a lot of financial effect is involved which over-do any advantage [if any].All the systems adopted have pros & cons.
5. Frequency also have major impact on Video [Films etc etc] as the number of frames/sec are different and for the same reason TV's standards.

1.
<<< bhankiii #2
The efficiency of switchers lies in their pulsed operation, not their magnetics. >>>

It is actually due to better Magnetic materials' efficiency which plays the part, due to their low loss & retntivity which allows operation @ Hi Freqs.

Post #1 & its reply #4,

From #5

<<< The Corps told me 25 Hz was more efficient for large motor loads, so that is why Mr. Woods utilised 25 Hz a hundred years ago, .. >>>

One thing which we forget is the Time-gap and developement of technology & materials, Manufacturing processes & more .. which should be considered seriously during discussions in commenting.

100 years before:
=================
a. can you imagine the quality of CORE Materials in properties, cutting & Finish; thickness and ....
We can not compare just raw iron sheets, their finish & magnetic properties with
todays materials' used at Power-Frequencies; say 50 Hz to 400 Hz [Leave Soft materials
aside].
Of cource with those poor resources wound-coponents [Transformers, motors, generators etc etc ] were more efficient at 25 Hz than at 50/60 Hz.

This was the reason with Mr. Woods to say:

" 25 Hz was more efficient for large motor loads".

Regards for all.

If we had a 400 Hz power plant connected to those AB Woods 25 Hz pumps maybe we could pump out New Orleans in 12 seconds next time.

I have an idea and please advice me if it is wrong: for the purpose of dimensioning the secondary maximum short circuit strenght it is better having a higher frequency as in this case, the impedance will be higher and will limit to a lesser value the short circuit current.

Am I right?

what ever the power is operating, it's designated to a power rating. an example being 415 V at a massive 25 A at 60 Hz. when you use a lower frequency say 50 Hz, your machine will not be able to achieve its highest operation speed.

if you reverse the combination, you run the risk of blowing something.

Will a motor designed to run @ say, 400hz draw, more,less or the same amount of power. Does the design frequency, have an effect on the size of the wire used for motor or trans former winding?

For information:

Among others, the Swiss railway network uses 16²/₃Hz.