Naval AC power 1

[ScottI2R]

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.

 

[zeusfaber]

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.

 

[itsmoked]

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

85% less CAST IRON is a lot less weight!

 

[IRstuff]

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

 

[afterhrs]

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.

 

[itsmoked]

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.

 

[Skogsgurra]

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?

 

[BJC]

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.

 

[Skogsgurra]

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

 

[itsmoked]

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.

 

[ScottI2R]

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.

 

[afterhrs]

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

 

[IRstuff]

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

TTFN

 

[afterhrs]

IRstuff,
Explain, I am always willing to learn!

 

[IRstuff]

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

 

[itsmoked]

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.

 

[itsmoked]

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

 

[afterhrs]

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

 

[IRstuff]

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

 

[wrong100]

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.