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Naval AC power

Naval AC power

Naval AC power

(OP)
Hi again all,
After talking with a few co-workers that were in the US Navy, I have learned that on board ship, a whole lot of the equipment used was powered by 400Hz ac. I was wondering why. Can anybody help?

BTW, one guy was an EWO, man, I couldn't believe some of the unclassified "techspecs" and capabilities he told me about! ((Unfortunately, he STILL couldn't answer 75% of the questions I asked (Still Classified!)...Guess I'll try "Janes"..))

Thanks,
Scott

In a hundred years, it isn't going to matter anyway.

RE: Naval AC power

Power transfer through a magnetic circuit (like a transformer) goes with rate of change of flux.

The higher the frequency, the more flux change you can achieve for the same level of peak flux, or more usefully, the lower the peak flux for a given amount of power transfer.

Lower peak flux allows for a smaller core cross-section without saturating your core, and hence more compact, lighter-weight devices.

Aircraft (where weight matters even more) use 400 Hz for the same reason.

A.

RE: Naval AC power

Restated all the transformers and motors are 85% smaller then their 60Hz bretheren.

85% less CAST IRON is a lot less weight!

RE: Naval AC power

MIL-STD-1399-300A is the military standard that specifies the performance of naval shipboard power.  While 400 Hz is the primary power, there's so much stuff that runs off 60 Hz that a secondary supply of 60 Hz power is almost always available.

TTFN

RE: Naval AC power

ScottI2R
    It has been over 10 yrs since I was on a boat(submarine). I will say that we used 400 hz for cooling
fans and various other "items." In my world, I
understood the reasoning to be a size driven issue and the weight was just an added benefit.    
    
Regards,
Afterhrs

Ask me no secrets, and I will tell you no lies.      

 

RE: Naval AC power

I was looking at a military field hospital generator during an open house.  It was run with a gas turbine. The generator part was the size of your typical cheap-o house generator with a 5kW rating.   I asked the technician if that was a 5kW generator.  He laughed and said, "No! It's a 55kW generator." I was dumbstruck.  I said, "how could that possibly be 55kW?!?!?"   His reply; It's 400Hz.   

RE: Naval AC power

I remember that most position feed-back in air-planes was via synchros in the old days. And those synchros would have been very clumsy and heavy if built for 50 or 60 Hz. The gyros and the "horizons" were fed with 400 Hz for the same reason. Also, the generator needed to supply them would have been unnecessarily heavy if built for 50/60 Hz. Why exactly 400 Hz and not 1000 Hz or something more musical, like 440 Hz, I do not know. Probably just one of those things that happened to happen?

RE: Naval AC power

One  reason for 400 cycle is Elmer Sperry - inventor of the gyro compass and autopilot.  A 400 cycle 2 pole motor has a synchronis speed of 24,000 rpm.  
A 208/120 system would run a reguar 120 volt,60 cycle electric coffee maker. I had to change the plug to some expensive plug from GSA stock but it made  coffee  in a Huey.

RE: Naval AC power

Of course! Gyros need high speed. You cannot get that with 50 or 60 Hz. Star for BJC.

RE: Naval AC power

Hey you can stick 60Hz to a 50Hz motor.  Has anyone stuck 400Hz to a 60Hz motor?  What happened?  I presume a 1725 might try to run  11,500Rpm... hmmmm not to happy I would guess.

RE: Naval AC power

(OP)
Thanks everybody,

Oh heck. I should have KNOWN that! Especially the aircraft implications. I guess I just need to THINK a little before I ask questions!

What boat Afterhrs? One of the guys I talk with a lot was on 614 as an ET. (Cannot recall the name of his sub.) At least THIS question to you is one that I absolutely would not know! :)

Scott

In a hundred years, it isn't going to matter anyway.

RE: Naval AC power

SSN-702 U.S.S Phoenix

It was an invaluable experience, I was taught this phrase that I still use to this day.

You get what you INSPECT, not what you EXPECT.

Regards,
afterhrs   

RE: Naval AC power

hmm...  the problem with that saying is that you'll also never get anything more than that, e.g., only low-side compliant.

TTFN

RE: Naval AC power

IRstuff,
    Explain, I am always willing to learn!

RE: Naval AC power

It's a well-known observation that given a tolerance band that's "tested," most operations wind up using the entire tolerance band and are generally at the edges.

The issues are many-fold:
>  It's expensive to catch problems and fix them after the fact.  Each step in a process accumulates value-added, which is potentially wasted as scrap or rework.

>  It's expensive, period, to inspect or test.

>  Lack of process control is often what forces the testing and inspection.

One of the major achievements of Japanese manufacturing in the 80's was the ability to control processing to the point where in-process testing and inspection were often unnecessary AND the tight process control actually had better performance than the traditional build/test/inspect processing used by US manufacturers.

TTFN

RE: Naval AC power

And still does!  That process was is called ZERO DEFECT manufacturing.  It comes down to involving the worker with the quality.. Get the workers to just flat NOT build in defects.  In Japan they are able to use the societal worker bee mentality. Works well there!   Here you often need to tie the workers pay to it.  Less defects? Company makes more, you make more.  That's the hope anyway. :)

RE: Naval AC power

Naval Power, is this like Prymid Power or the power of crystals?  :)

RE: Naval AC power

IRstuff,
    For the high volume manufacturing sector, you are absolutely correct. When it comes to many other arenas,
incuding the machines that are used for manufacturing,
I will continue to employ this philosophpy.



Very best regards,
Afterhrs     

RE: Naval AC power

Bottomline, most inspections and tests are a concession to the failure of process control.

When I worked at a semiconductor company, we routinely had 5 chip sites dedicated to test patterns for "process control."  Given that there were only about 80 die/wafer, these test patterns were an automatic 10% yield loss, since they were located in the prime area of the wafer.  We thought we had the process under control, but we were quite sadly mistaken.

Hitachi allowed us to second source one of their chips.  We asked them what the design rules, process parameters, etc. were.  They laughed and said it didn't matter.  Their design was so robust that they had no test patterns and were supremely confident that their design would work on any comparable process.  Sure enough, the 1st lot yielded the expected number of die, BUT, the second lot yielded substantially higher than any part we designed and built for our own fab.

TTFN

RE: Naval AC power

WHY NOT START FROM START.
EDISON HAD A PROBLEM WITH HIS DC SYSTEM.
SOMEONE (GUESS WHO, "T") DECITED 60 HZ
WAS BEST, AND COULD BE USED, AND TRANSMITTED
(IN WIRE) HUNDREDS OF MILES, (WITH TRANSFORMERS),
INSTEAD OF TENS OF MILES. EDISON WOULD NOT
ACCEPT THIS.
OUR MYSTERY MAN THEN ENDED UP AT A STARTUP
WHICH IS KNOWN NOW AS "G E". WHICH IN TURN
CHEATED HIM OF HIS MONEY AND INVENTIONS.

BACK TO THE QUESTION.

POWER IS USED ON SHIPS AND AIRCRAFT IN A
GENERAL FORM OF 400HZ, (DC 28V 270V 60HZ)
THE DC VOLTAGES ARE ALL RECTIFED AC 400HZ.

BENIFITS OF 400HZ.

1) IT IS EASY TO GENERATE AND DISTRUBITE.
(FIFTEEN % OF WEIGHT AND SIZE OF 60HZ)
2) ACCURACY OF SERVOS ETC. ARE 1/.16 = 6.66
TIMES BETTER. IF YOU ARE TRYING TO
CONTROL SERVOS,(TARGERT ON OBJECT WITH SERVOS).
3) WIRING LOSSES ARE LESS (PEAK CURRENTS
ARE 16%OF 60 HZ), AND FROM THIS IT TAKES
LESS POWER (LESS LOSSES).
4) IN GENERAL FILTERS TO KEEP UNWANTED NOISE
OUT OF THE POWER SYSTEM ARE SMALLER.
5) BOTTOM LINE. FUNCTION AND MONEY IS BETTER.

AD NOTE 400HZ IS NOT GOOD FOR GENERAL HOME,
TOO MUCH LOSS FOR MORE THAN SAY
(10,000FT) 2 MILES.

MYSTERY MAN GOT IT RIGHT.

RE: Naval AC power

On all the ships I served on the primary power was 60 Hz.  All the motors in the engineering plant, ventilation systems, etc. and all the lighting etc. were 60 Hz.  There was a small 400 Hz capability, either motor-generator sets or static converters for electronic and aircraft systems.

RE: Naval AC power

Will 400Hz actually waste more power in transmission or just make the system even more "distributed" (shorter wavelength)?

RE: Naval AC power

Blacksmith has it right.  I've been on or around Naval ships for around 32 years now and ship's service power is 60 Hz.  400 Hz is used for some electronics systems but everyday, run-of-the-mill stuff runs off 60 Hz.  

For Itsmoked: Naw, "Naval Power" is that force that grabs me when the wife wears one of those little crop tops and low rise jeans.  Still Crazy After All These Years.

DB

RE: Naval AC power

LOL,
Methinks that power emanates a little lower than the naval!

For Itsmoked re: applying 400Hz to a 50/60Hz motor.
Technically it would try to run that fast, although the shrapnel would likely kill you before you got a chance to measure it. Even if the bearings held up, the motor would have almost zero torque left.

"Venditori de oleum-vipera non vigere excordis populi"


RE: Naval AC power

Wrong100:

Can you run benefit No. 3 - "WIRING LOSSES ARE LESS (PEAK CURRENTS ARE 16%OF 60 HZ), AND FROM THIS IT TAKES
LESS POWER (LESS LOSSES)." past us again?

To my way of thinking, this would need six or seven times the working voltage, rather than six or seven times the frequency.

A.

RE: Naval AC power

blackwed, Thank you for that clear explanation of naval power. :)

jraef: All I can say is I wish I had a stiff source of 400Hz to jam into a 60Hz motor.  :(  

Especially since my experiments with running induction motors underwater are complete.

RE: Naval AC power

Once upon a time there were flourscent lighting system sold that ran on 400 cycles ( maby a little more).  The ideal was that 420 cycles operating a flourscent lamp gave you the most light for the energy input.
I don't know how they generated the 400 cycles, this was around the 1950s so I guess it was a generator.
Supposedly if your were lighting a large enough area it was economical.
IF I remember one of the aircraft companies in SOCAL had 400 cycle lighting.  It was one of those places with hundreds of engineers and draughtsmen in a room that went on and on and on.
Todays Electronic ballast excite lamps at 400 or more Hz.

RE: Naval AC power

Yeah, I think about 10kHz..

RE: Naval AC power

WELL THE TIME HAS COME , I MUST HAVE JUMPED
INTO SOMETHING THAT I KNOW NOTHING ABOUT.

ASIDE, FROM DOING THIS FOR 20 YRS,
GO BACK TO ORIGINAL QUESTION AND ANSWERS
1 THROUGH 6. THEY CONFIRM, WHAT I HAVE
SAID. (TWO FROM ITSMOKED)

I CAN SEE MIL SPECS ARE NOT REVELANT
TO A CONVERSATION ABOUT MIL SPECTS.

TRY 1399/? ,HAS ANY ONE DONE REAL EQUIPTMENT
DESIGN TO THIS STD. I HAVE (20YRS).
GOT A FEW THUMBS UP (CITATIONS) FROM THE NAVY.

LOOKS LIKE ITSMOKED SMOKED.

MY OBJECTIVE IS TO SHARE KNOWLEDGE,
IF THIS HAS TO BECOME A CONTEST, THAN 1000S
OF HRS CAN BE SPENT WITH NO BENIFIT.

FOR ZEUSFAFER POWER IS POWER 100 WATTS
IS 100 WATTS.
THE PEAK CURRENT OF A GIVEN CAP RECTIFIER
CIRCUIT IS DEPENDENT UPON THE CAP AND
THE ESR OF THE TRANSFORMER AND CAP CIRCUIT.
FOR A GIVEN VOLTAGE AND LOAD  IF I CHARGE A CAP 6
TIMES AS MANY TIMES THAN I WILL (AT 60HZ) I ONLY NEED 1/6 OF
THE CURRENT. FOR THE SAME VOLUME AND CAP AND ESR'S
400 HZ HAS 1/6 THE PEAK CURRENT IN THE TRANSFORMER
AND CAP.
MY CALCULATOR'S MUMBERS ARE 60/400 =.15.
O WELL 1/6 SOUNDS GOOD.
AT ANY RATE YOU CAN HAVE 6.6 (1/60/400) MORE WIRE,
IN THE TRANSFORMER (.15 ESR, (RESISTANCE))
WITH THE SAME PEAK CURRENTS IN THE CAP WHICH EQUALS TO
1/6.6 LOSSES IN THE TRANSFORMER.

DID I PASS YOUR TESTS, IF YOU MUST TEST ME
THAN DO IT. DO NOT GIVE ME A BUNCH OF GARBAGE.

WITH MIN 50 PS BASED ON THIS,
TIMES ABOUT 500 UNITS, TIMES AVG 1O YRS,
MY RAILURE RATE IS 50*500*(10*1 HR PER DAY =
91 MILLION HOURS. IF YOU EXTEND IT
TO 24 HRS PER DAY IT GETS BAD ONLY ABOUT
2 BILION.

NOT BAD. EVERY ONE
ELSE IS 10 TO 1,000,000 TIMES BELOW THIS
IN REAL NUMBERS.
HAVING PUT STUFF UNDER WATER, ON THE WATER,
IN THE AIR, IN SPACE, AND 5 MILE UNDER GROUMD.

ITSMOKED
 
DID I PASS.
OUT OF 400 + DESIGNS IN THE LAST 20 YRS
I HAVE HAD FINAL SAY ON ALL BUT ABOUT 50.
AMD I WILL CONSIDER THE FIRST 20YRS.

CAN YOU PASS.

I THOUGHT THIS WAS ABOUT INF.
NOT JUMP ON THE NEWBI.

hope NO ONE meets one of my designs.
there was a few of them on tv in the gulf war.
WH0 ARE YOU, WELL IT IS LATE AND I MUST
INTERVIEV A NEW ENG TOMORROW (TODAY).

"every time i go into a design i ask
if it failes, how many will die, will i be dead,
will it make us slaves,
how can i make it serve
what was intended"

A SORD IS A TOOL, GUTTING PEOPLE, CUTTING
GRAIN, IT IS STILL A TOOL

"LIVING IS EASY" FROM "PORGY AND BESS"
YES I READ IT AND SAW THE MOVIE.

BY THE WAY 100 IN MY HANDLE STANDS FOR 100%
WRONG THE FIRST TIME 100% RIGHT IN THE END.
WRONG ONLY MEANS THE CONCEPT WAS WRONG AS I SAW IT,
RIGHT ONLY MEANS THE CONCEPT WAS CORRECT AS I SAW IT.
PEOPLE DO NOT KNOW HOW TO THINK ANYMORE,
THEY TAKE WHAT IS FEED AND DO NOT UNDERSTAND
THAT EVERY ACCEPTED CONCEPT EFFECTS ALL OTHERS,
AND MODIFIES THE OVERALL PERCEPTION OF THE WORLD
THAT THEY LIVE IN.
PUT AN INCORRECT LINE INTO A PROGRAM
AND IT MAY GIVE YOU THE CORRECT ANSWERS UNDER GIVEN CONDITIONS, BUT WHEN IT IS USED WITHOUT LIMITS  
THE FLAW WILL SHOW UP.

RE: Naval AC power

Yeah, I think you passed all right.
I think your caps lock is pressed too.

RE: Naval AC power

WRONG100
It's a "sword" not sord.  Are we down to 99.44 % ?

RE: Naval AC power

SORRY I DID NOT REALIZE HOW TIRED I WAS.
AND WHAT I WAS WRITING, I HAD STOPPED WORKING (GETTING TOO TIRED).
AND THEN TRIED ANSWERING THE GUESTIONS.
NOT MY NORMAL SELF, (OUT OF IT).

A FEW FACTS, RUNNING 400HZ MOTORS ON 60HZ THEY BURN,
(TOO MUCH CURRENT). RUNNING 60HZ MOTORS ON 400HZ THEY SIT, (NOT ENOUGHT CURRENT).

BACK TO THE TRANSFORMER, ROUND NUMBERS FROM MY COMPUTER,
(BOTH USING M6 MATERIAL),
FOR 60HZ 100WATTS 1:1 (11.2WATTS AT 3.2LB).
FOR 400HZ (12.2WATTS AT .97LB), WITH THE SAME
VOLTAGE LEVEL.

MIL SPEC 1399 CALLS THREE TYPES OF PRIMARY POWER.
ONE FOR GENERAL USE, ONE FOR HEAVY STUFF, AND ONE FOR
SPECIAL AND AIRCRAFT. THE AIRCRAFT IS 400 HZ.

AGAIN, VERY SORRY FOR BEING SUCH AN ASS.
AFTER READING WHAT I DID, I CANNOT SAY HOW SORRY,
AND HUMBLE I AM. PLEASE ACCEPT MY APOLOGY TO ALL.
I HAVE A HARD TIME RELATING TO THE JUNK THAT I DID
BEFORE, BUT I DID IT.

WRONG100

RE: Naval AC power

Hahaha, Not a problem.  Thanks for the comeback.

RE: Naval AC power

Tired. OK. But release that caps lock. Please.

RE: Naval AC power

I still miss the ability to delete some of the things I've written here without tearing down the whole thread at the same time.

Going back to the "peak current" bit (don't like to let a learning opportunity pass by) - is this the surge of current that goes to top up a smoothing capacitor once every half (sixth of a, for 3 Ph) cycle if you're pulling dc off your system?

That would explain the difference of opinion - I had been thinking in terms of an ac load.

A.

RE: Naval AC power

I think you will understand the problem better,
if I generate a small table.

60hz        400hz        values
1.125       .75          core size needed in inches
441         150          turns needed for gauss
4.6         .91          avg resistance of wire
98          96           precent of use of bobbin area
3.245       .973         total weight (includes wire)
9.250       1.9          wire loss watts
2.016       10.3         watts loss in the mag. material
14.1k       13.9k        gauss

The only items I spec were fc (60/400),
voltage (115), current (1A), and after the computer
pick was made, I had to change the number of turns to get
the flux denisity about the same.
This material should be run at about 12k gauss at
this woltage level. Mil spec ,I would try to do
10k or 11k to be able to go 30% higher in voltage.
This is for EI cores with a sguare stack,
 (center leg .75 wide times .75 high).

Geting back to real designs, I would not
use either of these basic designes. too much
loss (temp rise, and too near the Bsat limit).

To answer the statement I made about
peak current losses, from the table you can
see that there is about a 4 to 1 ratio
in resistance (for the winding (copper loss))
which means a 4 to 1 ratio in
watts loss for the winding. This applies to rms as well
as pk currents.

I need to inject this, it may not flow
but it is revelant nowdays ( always with mil spec).
In a ps that converts ac to dc, there is a
concept called "power factor".
the best expresion is "real power/ apparent power".
For simple terms, a current conduction of 60% is
"NOT" a power factor of .6 (60%) in
a single phase system.

Some other losses get into the mix
as the currents and or HZ get larger.
If you are doing, a power loss (efficency), or
a temp related design, the "normal" design,
is to make wire losses equal mag losses.
The only way I can address this is to say
that it is in general correct for low fc designs.
As you can start to see, even a "simple"
60Hz or 400Hz transformer starts to get complex.

Once upon a time there were courses
you could take to understand "analog"
design. I have had sr. (20 yrs) design
know how, not understand the basic problems,
in a transformer, and power supply design.
As far as I know, less than ten schools teach ps,
and say only 4, have a complete spectrum.
Example (newbi from school) no concept of
how to cal a caps energy in a given system.
No general concept of temp rise in a component.
I used him to do "mean time between failure"
reports which forced him to learn the above
concepts and much more. That assignment
coupled with my guidence and other eng help
enabled hin to understand the real math side.
When he was ready we next started him doing
pc card layouts and making it work.
(You canot do 20amps with a 6 inch loop at 10ns.)
The only real problem he has remaining is magnetics.
I have been trying to teach him, it will happen soon.
He understands the magnetics it just will not fall
into place (click).  Once this happens he needs
to unify all of this into a overall understanding.
Once he gets there he will be able to do any design.
Note: he should surpass me and all the designers
that I know,  some are considered the best
in the U. S. Than he needs to update his technology.
We are about ten yrs behine.
When he gets there I hope he stays with us.
This has been a 4 yr teaching.
As eng mag I can only do job assignments and
show how they should be done.
As a person I try to connect with him and understand his problems, and also show him all of the aspects of
coping with companies such as BO and RA.
At this stage of my life "62" sharing knowledge
(while it has always been a large part of it)
has taken on a different aspect, (this is my third
teaching, and must be my last).

I debated to myself about putting this last
segment in, but after readin the context
I decited that I should. It is a flow that just
came out, and I think gives the reason we are
all here. We all want to share "know how".

Personal note, I do thank you for your
understanding, and again sorry for the
stupid reaction.

RE: Naval AC power

I, for one, feel as though I recieved a valuable lesson in 400Hz theory and application today. I'll probably never use it, but the next time someone asks me why, I'll have better answers. Thanks to all.

And thanks for releasing your Caps-Lock key Wrong100. If you're like me, I struggle with my "advanced hunt-and-peck" typing skills, so I tend to use either all caps or no caps in emails rather that have to keep going back to fix things. But posting in this forum has forced me to develop better skills because I too found that people don't like it and tend to marginalize those that do it.

"Venditori de oleum-vipera non vigere excordis populi"

RE: Naval AC power

No problem, although, you don't need to manually insert carriage returns, either.  The HTML display handles that pretty well.  In fact, your postings have almost all wound up looking like they were formatted for a newspaper display, whereas, on most people's browsers, the display window is actually double or triple what you formatted.

PS.  thanks for the info..

TTFN

RE: Naval AC power

(OP)
WOW!
What did I start here everyone? I cannot believe the overwhelming response (in quantity and especially QUALITY) to the question I posted. I cannot thank you all enough. I HAVE been "learned" you might say. This is without a doubt, the most valubke forum I have ever joined. I hope that in the future I will be able to contribute something worthy to someone else just as everybody here has to me.
Thanks again all,
Scott

In a hundred years, it isn't going to matter anyway.

RE: Naval AC power

Good to see some old-timers participating in the forum, bad that a lot of their information/knowledge is going out of the trade after their retirement.

Thx for the info wrong100

RE: Naval AC power

If I may put in my two cents worth here.

I am not a military man, but it seems to me that most military power has to be self contained, mobile, light weight and compact. Airborne, marine, or vehicle mounted, the one aspect is that it must all operate well away from the national power grid.

400 Hz has a lot of advantages mostly for wound components, alternators, transformers and motors. All will be much smaller,lighter and more compact.

A very good example of this is the ordinary humble automotive 12v car alternator. They are very compact for something that may be rated at 14v and maybe 60 amps. Not a lot of copper and iron in there either. They do it by running at a much higher than "normal" operating frequency.
 
But 400Hz has one big disadvantage over 50/60Hz when it comes to very long range power distribution. Problems of surge impedance and resonance, standing waves and other nasty effects can become problematic when you start trying to send 400Hz power over tens or hundreds of miles.

For aerospace 400Hz is definitely the best way. Aboard ship weight is not going to be such a big factor, and I would expect normal commercial 50/60Hz standard voltage machinery would be more economic to buy and install.

RE: Naval AC power

Aboard ship weight is not going to be such a big factor, and I would expect normal commercial 50/60Hz standard voltage machinery would be more economic to buy and install.

Warpspeed - that's it, in a nutshell.

Blacksmith

RE: Naval AC power

Blacksmith,

Aboard ship, weight may not be a huge factor, however space certainly is.  Every cc of space taken by a transformer is one less cc of fuel, cargo, ammunition, food, living space...ad nauseum.

Back in the good (bad) old days, the same radio which sat in a PBY was probably in the radio shack on a Cruiser as well.  Either a DC to DC motor-generator (Dynamotor) was used for the mobile plate supply (we’re talking about hollow-state technology here) or the radio was designed to operate off 400 Hz aircraft power.  Often the equipment was designed to have external supplies (the old TCS transmitter comes to mind) for each application.

When it comes to tubes, some like the 4CX250 came in a couple of flavors.  One had a 24V heater for aircraft use and the other with the 7 V heater.  Again, the 24V tube would draw less current than the 7 V unit.


Wrong100, thanks for the wonderful explanation.  I reminded me of myh father's explanation nearly a half century ago when I asked why the surplus selsyns ran on 400 Hz.  Dad taught Electronics for the  Navy.

I remain,
The Old Soldering Gunslinger

RE: Naval AC power

Thanks Wrong100.

Having been the first one to mention that higher frequency meant less peak flux, it was a bit dim of me not to recognise that that meant fewer turns.  Guess I've forgotten more than I'd realised in the 20 years since I last worked on power systems.

A.

RE: Naval AC power

I have just thought of something else, skin effect.

With dc current the current flows through a conductor evenly through the whole cross sectional area. With ac current the continuously changing magnetic field causes the current to crowd towards the outer "skin" of the conductor. This effect is highly dependant on frequency, and it becomes a limiting factor with high currents at high frequencies.

That is another good reason why it is not practical to transmit thousands of amps of 400 Hz power over very long distances and why 50/60hz is better for that.

RE: Naval AC power

Thank you for your "yea".
glad it served. makes me happy to see that you understand.

I just spent 2 hrs writing a thing on pk current,
than I got shut down.
tried to recover, "No".

Is this normal? Not trying to be flip,
but some of the concepts need time to explore
and I am a very slow hin pecker (typer).

Nutshell ;
C=i*t/v  been told no, (but math is yes) it works and is valid.
Use the falling voltage of the rectified  form

I hate to do this but (short answer) results for
pk current are 60/400 = .15% for a given
ripple voltage with the same cap value and esr.
So acording to the above math, for a given C
if you increase the fc at the same load, ripple
decreases. If you do it the other way, for a given
ripple voltage and current the amount of cap decreases.  

Understanding is a time and absorbing thing (remember all things in elec are related to all other things).

If you do not understand I will try to make
it clear.
Now almost 4 hrs on line  (typing and
clearing thoughts so people can understand, I do need to
make my thinking into a more specific order)
 "go to bed".

I do enjoy this, but I am "upset" about being cut off.
The only way I know, is to explane in a logical manner.
This takes time, (if you cannot relate to your subject,
and person "people" every thing else is for not),
now you can see why and how I call myself a teacher
and why I was so upset
(about what I had written before).
All I do is give them the links to knowladge they already have (how to put it together).
Good will to all.

RE: Naval AC power

wrong100,

If you are having problems maintaining a connection with the site long enough to form your message, perhaps you could type it in Word/Word Pad/Notepad, some other text program, and then do a copy and paste into the forum message box.  By the way, you can skip using the 'Enter' key except at the end of your paragraphs.  The software will take care of wrapping the words onto the next line.

RE: Naval AC power

wrong100, davidbeach is correct!! If you are going to embark on a relatively long post by all means write it in WordPAD or Notepad or any other word processor.  Then you can spell check it or abandon it for the night so you don't muddle it up. You can come back to it the next day. Re-read it, touch it up.  Then SAVE IT.  Then just copy and past it into here.

ALL of us have had our posts evaporate.

It is very annoying, almost shocking.

Remember that as you are typing your post in the window you are really just typing it into your WEB browser.  When you submit it or preview it then it goes to the web... Well the site can go down for maintence or because its buggered or whatever over that long period you are typing and then your work is piffed.

Thanks BTW for your efforts.

RE: Naval AC power

Hi people
I am trying the suggestion of wordpad. Thanks.

I will do the last item on the list , plus two others.
If you start with a wire in free space it will generate
a magnetic field around it.  As you get futher away
from the center of the wire the mag field is less,
(the same rules of radio transmittation)
To make a very very long story short, the very
center of the wire (due to the induced mag field)
opposes the flow of current. This makes the center
of the wire not as conductive as the outer edges.
The result of this is most of the current flows on
the outside of the wire (on the "skin"). Sence the
conductivy (call it effective area of wire at the fc) of a given wire,
is dependent on the "active (cross section)" wire. The higher
the frequency, the more loss in the wire, compaired
to its dc conductivity component.

At one time I used a "MS BASIC" program that I
had written to calc skin effect, yes that important.

Form my previous comparesion  of 60hz to 400hz transformers
the numbers are for 60hz  = .358 inches, and for 400hz
= .1377 inches (this is the number which states the   "ratio of loss")
(this is about the 50%  loss nunber ? level if I remember).
While  this is not much for home use
(most home wire is less than .133in in dia) too small
at 100 amp in out, think of power companies).
Lets see .358/.1377 = (1.599-) call it 1.6 times. This loss ratio is
per inch, or foot, or mile or 1000 miles. If I could reduce my losses
to 1/1.6 = 1/.625 = .375%. I know I would do it without thinking.

Put it another way, if you were designing a power system, ( for a power co.)
and had to put 10K or 100M amps (in a wire) this would be very important in
your transformer design and wiring. That is why power conpanies
try to do the best answer (for them the answer is 60hz).
For them 60hz  is the best answer, of the tradeoff of total energy
transfered verses size, fc. etc.

Skin effect is related to fc numbers but it is also by nature
related to current, for losses  (I^R) it is a resistance rato at best.
1 amp (losses) are  dfferent than 100 amp losses, (the square factor of current).
What is not said, is if you are designing a 60hz or 400hz
transforner, unless you get to the .1inch wire dia do not worry (min  effect)
unless you are pushing it to the limit, where 10% is a make or break thing.

How about a new concept (problem) with wires.
 
If you extend  the concept  of (skin effect) to related wires in a coil,
you end up with a concept of wires carrying currents next to each other.
Start over except that all of the concepts about skin effect apply.
Proof is, what is the difference in mag flux and its control of resistance
based on the center of a wire (take a  number .1(skin )),  
verses a wire placement .02inches,  removed from the center of the wire.
 This is called the proximinity effect. The result is it still pushes the wire
current into a smaller portion of the wire, only now to one side.

The third major effect is due to ac currents generating voltage (and therefore)
current loops within the magnetic material as well as in the wiring.
This is eddie current effects, and can be very lossy.

The result is,  if a wire has current  
in it, it is subject to many various effects, (these effects can be  most dominant).

Just to make sure that you understand the results of the concepts.

A design for a 1000 watt transformer "can have (10watts 100watts 1000watts loss)."
It all depends on the base magnetic losses as well as the, fc, wire size,
nunber of strands, size of strands, and on and on, than you get into the mag material,
where it starts all over again.

Yes I understand ,  the original question was answered.

Question is did you learn anything, or was it too much and became
just words.
 
Have expanded it with your approval ?

My concept is to let you be exposed to the problems involved  
in a 60hz verses 400 hz transformer, and the base concepts that
drive these designs (which are not throught without an unstandering
of  the higher fc components, as well as the low fc components).
Like most things, there is no set answer .
I have had eng tell me that they have had two inch dia
bolts melt due to eddie current losses in large 60 hz units.

I am just trying to expose you to something more than  the
"yes, no" answer
 Did any of this make sense?.

I think my head  hurts, not a normal ake, it just hurts thinking
about all of the concepts explained, and not explained.

One thing to the general public (and you mil people in specific)"I design to the mil specs, but am not in the mil".

"LOOSE LIPS SINK SHIPS".
I have been waiting 50 yrs to be able to put this in contex.

I think this runs over 3 or 4 days, hope it is not too much,
I still do not know how much you want, please let me know.

Oh I almost forgot, more detailes can be found if you do a
specific search for "UNITRODE" added words "SEM",
go directly to the "TI\FOCUSE" website, (HANG ON TO
YOUR MIND), it gets very complex very fast, but many good
things can be understood (pick and chose).


Next or not, what to go to now.

RE: Naval AC power

Thanks yet again wrong100.  Seems the wordpad method worked! :)

This stuff came up in college.  It's great to get a reminder and the applied angle as apposed to the theoretical angle prevalent in school.  Skin effect is generally taught about a wire running through free space NOT in the context of a coil as you have done.

Now you're making me think..  If you have a multilayer coil of wire (like 30 layers) and you are operating at a frequency where skin effect is significant are you saying the skin effect normally present on a single wire is now different on the wires in the middle of this coil verse the outer wraps and the same with the inner most layer?

RE: Naval AC power

Skin effect exists in all conductors carrying ac current the wire does not have to be formed into a coil. The mechanism is the building up and collapsing magnetic field around a conductor with each half cycle. This drives the bulk of the current to the outside edge.

Skin depth is generally measured as the depth above which 95 % of the current will flow. Skin depth in mm is roughly 66/Hz^0.5  This effect may be completely ignored if the cable diameter is less than twice the skin depth.

Skin depth at 60Hz = 8.5mm
Skin depth at 400Hz = 3.3mm
Skin depth at 20Khz = 0.46mm

If you wanted to send vast amounts of electrical power over a long distance you would try to use as high system voltage as feasible, but also the conductor diameter should not be appreciably more than twice the skin depth. That limits you to the size and current carrying capacity per conductor.

In practice the ac resistance of a thicker conductor is higher than the dc resistance because the whole cross sectional area may not be efficiently used to carry the current. For very high frequency conductors, flat strips and foils are often used, or sometimes even hollow tube, or bundles of thin wires insulated from each other (Litz wire). All these have a large surface area. For high powered radio transmitters silver plated parts are often used. The silver plating carries most of the current.


 

RE: Naval AC power

Yes
squared I think, also prox is squared per layer if I
remember (it is squared for the second layer). I just kind of push buttons now.
The first hf trans took about 2wks (1 pass needed 20).
I got smarter, rearanged some gen math,
got it down to only two days (1 pass).
Did that for a couple of years, than bought a
program.

"confirmed" the program and all following updates.

You must know how the program is doing math.
Kind of like using a slide rule, if you do not
know where your answer should be, how do you know
if it is correct.
If it seams too good it probably is. Aside from
program updates I have only had to do about 1 a yr
for the last seven or eight years (most not critical).
That being said I have about 3 or 4 that need to be done
in the next week,"checks"(do not like the computer answers).
I just noticed it is about 4am must go.

I did manage a couple of other posts,but cannot do long
answers for a week or two.
later

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