Has anyone heard of a 3-Phase 120VAC Delta system? I "believe" it is used on ships (Naval ships).

If so, where can I get info about it?

Don't know much about it, but if memory serves correct I have only seen it once in 400Hz on a non operational and aged generator.

Back in the 80's I quoted some military ships with 120 delta systems, I believe they were mine sweepers. I also remember a panel for a plastics company that had their process heaters in a 120V delta arrangement.

120VAC delta systems, both 60Hz and 400Hz, are indeed used on Navy ships, as is 450VAC. It's pretty much like 240V delta systems except the voltage is half. I don't recall any actual 3 phase loads running at 120V.

I spent some time in Uncle Sam's Canoe Club, so maybe I can be of some help. What kinda info you looking for?

Radar - EM2(SS)


[This message has been edited by Radar (edited 06-09-2006).]

In the Royal Dutch Airforce we used 115 V ac delta at 60 Hz and 400 Hz.
This was generated by diesel gensets or a 380/660 star delta rotary converter from the POCO mains.

The other Voltage was 416 Volts at 400 Hz for 3 Ø motors and hi power equipment.

So probably its the same as 120 / 450 Volts system discussed here for military applications.

Regards

Raymond

I was another member of the "canoe club"

The carrier I was on, used the 120 V ungrounded delta to power up 120 V convience outlets and lighting. The delta requirement meant we could lose a single phase and still be able to power up 56% of the load. The ungrounded requirement meant that we could have one phase to ground fault and the system would still function. Both of these requirements were used to make the system fault tolerant.

We were repeatedly warned that just because the system was not referenced to ground, that is was _NOT_ safe to touch the energized phases. There was more than enough leakage current between each phase and ground to kill a person.

LarryC

editted to add missing word

[This message has been edited by LarryC (edited 06-09-2006).]

Radar -

A friend of mine (electrician C-10) was asked to service a "target ship" that was had fried some sort of electronics circuit board. The Navy wanted Dan (my friend) to check the electrical system as they did no want to just fry another board (several thousand dollars for this board).

This is from "memory" so I may not have it all correct:

The boat had 480V 3-phase with each phase going to a separate transformer that put out
240/120V. Dan said that there was no “neutral”. He also said the voltages were really “strange” from phase to ground (I don’t recall the voltages) and were well under 120V.

I think he also said that phase to phase measurements were 120V.

I talk with him a second time and he said he had spoken to a “Square D” rep who when told of the particulars asked if it was a ship and especially if it was a navy ship.

LarryC –

What carrier were you on? I was on the USS Ranger (CV-61) with the Marine A6-E squadron for the 1987 and 1989 WestPacs.

All –

Thanks for the info. One doesn’t get to see (and I didn’t get to personally) these sorts of strange things everyday, but it’s great to be able to toss out a question here and be able to get good answers.

Steve

Not quite the same thing, but in the U.K. large building sites often employ a 3-ph transformer which has a Y secondary, 110V between phases, 63V each phase to ground. The neutral isn't used, with all the 110V power tools on site being connected across two of the three phases.

skingusmc -
USS Enterprise (CVN 65) 85 & 86 WestPacs

Ships power was 480V 3 phase Delta, with 3 single phase 480-120 transformers hook up as delta - delta to provide 120V lighting and outlet power.

Like I said before, no phase was bonded to the hull, and that was for battle damage reliability. Also the ship was designed and built back in the late 50's and early 60's.

US Naval ships use 110V 3-wire Delta power. I've heard variably that it's for safety (flooded compartments are safer with 64V than 120V live wires) and alternately for reliability in the marine environment (not sure why). Anything requiring wye or 220V, etc, is wired up with a dedicated transformer. The hull is always used as a safety ground; the only equipment that gets wired with an actual safety wire are plastic insulated cases that can't be directly bonded.

Distribution from the load centers is 440/255V delta for HVAC and distribution in general, with final step-down to 110V Delta. All 1-phase equipment onboard the ship (including convenience receptacles) is wired up 1-phase "delta" with two hot wires. This presents surprisingly few issues, despite being the white wire being live (not to mention 110V vice 120V); I can't recall a single issue with any commercial equipment and shipboard power from the neutral being hot.

And yes, it is 110V, not 120, and 440V vice 480. A lot of aircraft use 400Hz (220V wye IIRC, but don't quote me on that), so you see this a lot on ships as well, as it's often cheaper just to use aircraft equipment for a similar purpose onboard ship than to design something specifically for the ship. And no matter how many times I see it, the concept of an electric-powered generator always makes me chuckle

Also, NEC does not apply; the planning yard engineers have final say.

[This message has been edited by SteveFehr (edited 06-10-2006).]

"the concept of an electric-powered generator always makes me chuckle"

Don't laugh too hard, it may be the future of generation by manipulating efficienties. I had the idea in a science class when I was a kid (You know the free energy dream), and recently read a research artical on it being studied now. (Cant find the artical...) But the concept was operating generators as rotating transformers to stabalize load and PF when using wind, solar or wave energy generation instead of invertors.

On a submarine those generators are what save your life. You have two motor-generator sets. One running AC motor, Dc gen charging the battery, and the other DC motor, ac Gen supplying the bus, thus keeping a good float on the battery. If you lose the AC bus, the MG's default to DC motor, AC generator, because the battery now has a higher voltage, thus current leaves it, and saves our lives.

Back to Steve's question for a minute. As noted by Larry and others, the 120V system is pretty much for convenience outlets and lighting. It's a 120V (or maybe 110V) plain delta, meaning there is no neutral. And as mentioned above, there is no bonding of any point in the electrical system to ground (hull). So the electrical systems float. You will read 120V phase to phase, and unpredictable values phase to ground because the electrical system is floating. Same with the 450V system, you'd read 450V phase to phase but unpredictable voltages between any point in the system and ground (hull).

The floating electrical system is for tactical reliability, meaning you can inadvertently have a ground occur at any one point in the system with no effect on operation. There are permanent ground detection systems in place that are operated hourly so if a ground does develop, it can be cleared quickly. Obviously a second inadvertent ground would make for a really bad day.

So imagine this for a moment - you could, if you really wanted to, cut the ground bond on a 240V delta, and the delta would continue to work fine. You would loose basic important safety features, a most serious issue, but the system would work. Shipboard systems are just like that except they have 120V transformer secondaries rather than 240V secondaries.

Shipboard circuit breaker and/or fuse panels that are 120V all have 2 pole CB's or pairs of fuses for each circuit. As I said, it's just like a 240V delta except half the voltage. With no neutral, you need to break both sides of the line.

Don't everyone freak out here - but as best I remember I thing the 3 phase color cose was: Black / White / Red.

So with no system grounding and/or neutrals to worry about, checking the electrical system is somewhat simplified. Phase to phase voltages need to be stable, equal and clean. On my boat the turbine generators and the motor generators supplied 450VAC, the operator (me) had voltage regulator adjusting knobs so one could run the voltage up or down a bit (can't remember how far). The 120V systems were supplied by stepdown transformers from the 450V bus, so a voltage spike would seem unlikely. Plus, a 20V variance on the 450V side would amount to about 5V on the 120V side. So I don't know what else there would be to check so far as the electric system goes.

We did have a static inverter, I think 120V. It had lots of problems so we did not use it. But something like that might cause enough electrical system problems to affect other components. You might ask about that - if there is one in this case.

OK - long enough for now I reckon, someone else's turn. By the way Steve, I may know you. Do you happen to work for a large LA area contractor and assigned around the Union Station area downtown? Or used to be anyway?

Radar

Nope, sure don't, I've been around the country/world a lot for a few weeks at a pop, but I'm a GS civilian DoD engineer and have only ever worked in Norfolk/Portsmouth, VA. I used to work mostly shipboard electronics, but I'm working almost exclusively on shore-side power now. (Working 100% on US navy installations and being the senior responsible engineer means never having to worry about pesky codes or inspectors, heh)

Thanks for the explanation of the inadvertant grounding, that makes a lot of sense; I don't know why I didn't think of that myself And yes, Black, White and Red are Phase A, B and C! No such standards for connector pinouts, unfortunately. Has lead to some "issues" in the past, especially when the equipment manufacturer doesn't wire their UPS to the pins their drawings say they did, then switch halfway through the production run and begin to do it "right" but don't tell anyone about it...

[This message has been edited by SteveFehr (edited 06-11-2006).]

That is also a common color code in old industrial systems for 3 phase power.
Don

Wrong Steve, Steve. I wasn't seeing there were multiples here, I was refering to the Steve that started this string (skingusmc).

Sorry for the confusion, I'll try to pay more attention next time.

Sounds like an interesting job tho. I really kinda miss the shipboard stuff and the ocean and all. Oh well, I've drifted off topic far enough.

Radar

Some old Amtrak passenger cars use 120V 3PH corner grounded delta systems. I am not sure about the Horizon , Superliner or Amfleet cars but I know that a lot of the cars that were bought from other passenger RXR are of the corner grounded varaity.

I have a 35KW gasoline egine powered generator that came off of a Naval Ship. It was built by Hobart and I can only guess its age to be somewhere in the 1930's or 1940's because of the fact that engine is a 6 cyl flathead and it just looks like it came form that era. The funny thing is that the engine has no identifying marks on it anywhere as to who made it. Is anyone familiar with any of these gensets? The generator is a 120V Delta 3 Phase, but I am not sure of the frequency whether it is 60Hz or 400Hz. I am told that you can count the number poles (just the same as in any AC motor) in the generator to determine the frequency. The generator runs at 1200rpm. What am I physically looking for inisde the generator so that I can count the number of poles? Does anyone know where there is a picture that shows me what the poles look like?

If the generator is running, and you are getting 120 volts out, a quick and dirty test method is to plug in an electric motor clock. Time the clock for a few minutes and if it is close to keeping time, it is a 60 Hz output. 1200 rpm is correct for a 6 pole 60 Hz machine. If you have or can borrow a Fluke 80 series multimeter, there is a HZ function when measuring AC Voltage.

LarryC

Kinda drifting off topic a bit here, but what would happen to the 120V (60Hz) clock if it were connected to 120V 400Hz? Kinda like a time machine??

I was thinking, if the genset was runnable, start 'er up, borrow a scope and have a look at the wave shape. Should be simple enough to tell 60Hz from 400Hz.

NOT RECOMMENDED - but from my personal experience, inadvertant touching of the hot leg on a 400Hz source hurts a lot less than the same 120V 60Hz - more skin effect I think, less current penetration thru the skin.

Radar

Radar -

"Back to Steve's question for a minute. As noted by Larry and others, the 120V system is pretty much for convenience outlets and lighting. It's a 120V (or maybe 110V) plain delta, meaning there is no neutral. And as mentioned above, there is no bonding of any point in the electrical system to ground (hull). So the electrical systems float. You will read 120V phase to phase, and unpredictable values phase to ground because the electrical system is floating."

This is exactly what my friend Dan described. And that there was no neutral.


"Same with the 450V system, you'd read 450V phase to phase but unpredictable voltages between any point in the system and ground (hull)."

I don’t think he said anything about this, so am not sure if he measured it or not.

Thanks all for the info.

Steve

Radar, I suppose it is just a personal thing but when I got bit by 400hz on ships I thought it was worse than 60 hz. It sort of makes your ears ring instead of that old familiar hum.

It might possibly be that there was some degree of inebriation factor at work too. Back then anything was possible.