Frequency and the world

[steelersman]

"Sacked 47 times last season, Roethlisberger is on pace for almost 58 this season, which would set a Steelers record."

As long as they keep increasing the number in the win column by 1 every week or so then I don't care how many sacks he takes.

 

[JJWalecka]

Our hopes were crushed in the first quater of the first game of the season........ LOL

I laugh cause I don't want to cry anymore.

JJ

 

[broadgage]

In the distant past, a number of frequencies were used in the UK, and a commitee was commisioned to report on the matter and produce a report, known as the WEIR REPORT after the chairman Mr. (later, Lord) Weir.

Frequencies of 15, 16.6, 25, 40, 50 and 60 cycles were in use.
The lower frequencies were favoured for electric railways and heavy industry, since at the time large motors were not satisfactory on higher frequencies.
In Belgium the railway still uses a frequency of 16 and two/thirds cycles.

Low frequencies were not very suitable for lighting since the flicker was obtrusive especialy on low power lamps.
This was not that important since a DC supply was often used for lighting. (if a light had to be worked from a low frequency AC supply, sometimes a transformer was used to light a 6 volt vehicle headlight bulb which had such a thick filament that it would not flicker)

The Weir report recomended that all new schemes should be at 50 cycles, 3 phase, 4 wire, 240/415 volts.

Higher frequencies allow for cheaper, smaller motors, generators and transformers, but increase capacitive and inductive losses.
If generating at 50 cycles then the maximum speed the alternator can turn at is 3,000 RPM . At 60 cycles it is 3,600 RPM, which is slightly more efficient in the case of gas turbine or steam drive.

 

[Besoeker]

In the distant past, a number of frequencies were used in the UK, and a commitee was commisioned to report on the matter and produce a report, known as the WEIR REPORT after the chairman Mr. (later, Lord) Weir.

Frequencies of 15, 16.6, 25, 40, 50 and 60 cycles were in use.
The lower frequencies were favoured for electric railways and heavy industry, since at the time large motors were not satisfactory on higher frequencies.
In Belgium the railway still uses a frequency of 16 and two/thirds cycles.

Low frequencies were not very suitable for lighting since the flicker was obtrusive especialy on low power lamps.
This was not that important since a DC supply was often used for lighting. (if a light had to be worked from a low frequency AC supply, sometimes a transformer was used to light a 6 volt vehicle headlight bulb which had such a thick filament that it would not flicker)

The Weir report recomended that all new schemes should be at 50 cycles, 3 phase, 4 wire, 240/415 volts.

Higher frequencies allow for cheaper, smaller motors, generators and transformers, but increase capacitive and inductive losses.
If generating at 50 cycles then the maximum speed the alternator can turn at is 3,000 RPM . At 60 cycles it is 3,600 RPM, which is slightly more efficient in the case of gas turbine or steam drive.

Informative as always, Broadgage (railways?).
Do you have a link to that Weir report?

 

[JJWalecka]

I appreciate all the info. It?s a different perspective on the standards of electricity.

How is the economy out in the Isles?


JJ

 

[Besoeker]

I appreciate all the info. It?s a different perspective on the standards of electricity.
How is the economy out in the Isles?
JJ

A bit like most places, I suppose.
For Hokaido and Honshu:
Uncertainty has now hit Japan. In the past seven days the Origami bank has folded. Sumo bank has gone belly up and the Bonsai Bank has announced plans to cut some of its branches. Yesterday it was also announced that the Karaoke Bank is up for sale and going for a song while shares in Kamikaze Bank have nose-dived. The Samurai bank is soldiering on after sharp cutbacks. Five hundred staff at the Karate bank have got the chop and analysts report that there is something fishy going on the the Sushi Bank where it is feared staff will get a raw deal.

 

[dbuckley]

Coincidentally, I'm currently reading the British book "Electrical Timekeeping" published in 1940, author is F. Hope-Jones, MIEE, FRAS, mate of Einstein. There is a chapter in this book entitled "The national time service provided by the grid, and the regulation of its frequency to average Grenwich Mean Time"

F. Hope-Jones stated in 1895 that if clocks used synconous motors their timekeeping would be syncronised to the frequency of the electrical supply. In 1927 the Central Electrical Board was set up for whom the Weir report was produced. After the UK settled on 50Hz as noted above, the requirement for frequency stability was set at 2.5% allowing syncronous clocks to be up to half an hour a day out. By 1937 the requirement was 30 seconds per day.

It is noted that the Yanks got there first(!) in around 1918, Mr H.E. Warren of Ashland Mass. designing the mechanisms necessary to keep the alternators running "on time".

 

[iwire]

Higher frequencies allow for cheaper, smaller motors, generators and transformers, but increase capacitive and inductive losses

Which I believe is one of the primary reasons many aircraft use 400 hz.

 

[dbuckley]

For aircraft the prime driver is weight - a 400Hz tranny is much lighter than a 60Hz or 50Hz unit and I assume the same is true of alternators.

Years ago before gas prices got all silly I read somewhere that for an aircraft that flies international routes the cost to carry a sachet of sugar is $5 per year, and thus airlines are very careful about what they carry...

 

[Besoeker]

For aircraft the prime driver is weight - a 400Hz tranny is much lighter than a 60Hz or 50Hz unit and I assume the same is true of alternators.

True for alternators and rotating machines generally.
We make high speed motors and the VFDs for them. These are typically 20,000 rpm and used mainly on machine tools. The prime driver in this case is to reduce size and, more critically, rotor inertia to give the high dynamic performance required.

 

[LarryFine]

The prime driver in this case is to reduce size and, more critically, rotor inertia to give the high dynamic performance required.

Wouldn't the higher speed counter-act the reduced rotating mass?

 

[iwire]

For aircraft the prime driver is weight - a 400Hz tranny is much lighter than a 60Hz or 50Hz unit and I assume the same is true of alternators.

Exactly what I was pointing out.

The fact the the higher frequencies increase capacitive and inductive losses is not an issue when none of the circuits are very long at all.

 

[Besoeker]

Wouldn't the higher speed counter-act the reduced rotating mass?

Not as a rule.
Very roughly, if you half the radius and double the speed you'd get the same power but 1/16 the inertia.

 

[LarryFine]

Very roughly, if you half the radius and double the speed you'd get the same power but 1/16 the inertia.

 

[Besoeker]

Not really unless you're into that kinda thing.

 

[JJWalecka]

Interesting ?yes?.I guess I'm guilty too.

JJ