What type of railroad three phase delta with only two conductors did I observe?

[mdlueck]

Greetings,

This forum has been of significant benefit already sorting out one type of pole mounted transformer I observed. Here goes with another....

Railroad signaling and powered switch utility feed. The meter says per a utility label: "Three Phase Three Wire Delta". However, I only see two wires feeding the meter! (Single phase triplex.)

And one of the wires is bonded to ground.

The transformer mounted to the board has the following label. I figure that transformer is performing 240v / 120v/240v... basically adding the center tap ground that is missing with the Delta primary. Correct?

The utility pole transformer has insulated wires connected to both sides, nothing to the center tap.... and the bare ground is connected to the same bushing as one of the two insulated wires in the triplex! So that bushing gets pulled to ground, the other rises to 240v to 250v?

So the utility's "Delta Primary Service" is a single hot leg at around 240v to 250v? How exactly is "one hot leg" constitute a "Delta service"?

I know full delta, I know open delta, but this.... is a stretch to understand. Please again kindly do so.

I am thankful,
Michael Lueck

 

[LarryFine]

It looks like 240v 1ph to me.

 

[jim dungar]

You have a single phase service.
Could be an old meter.

 

[mdlueck]

Judging from the pole transformer connection, do you think I am concluding correctly that the one insulated conductor that also has the ground connected to the same bushing is truly ground, and thus the other insulated conductor has the full 240v?

I am thankful,
Michael Lueck

 

[LarryFine]

Yes, but definitely not sure enough to proceed without measuring it for yourself.

I'd want to see inside the disconnects anyway.

 

[mdlueck]

Yes, but definitely not sure enough to proceed without measuring it for yourself.

I'd want to see inside the disconnects anyway.

That, my friend, will never happen. That railroad crossing is right next to a county park....

"Historic Bridge Park of Calhoun County, Michigan - Visitor's Guide"

Historic Bridge Park of Calhoun County, Michigan - Visitor's Guide

A concrete bridge goes under the Michigan Central track between Chicago and Detroit, then I walk back the surface country road, pass the signal and powered switch at the East approach to the Battle Creek yard... which this configuration is powering that. Then pick up a park trail (not listed on the map) which leads to the #6 bridge.

Park suits me fine.... I am interested in both railroads and old bridges.

I did just get back from catching the last Amtrak for the day going through the Kalamazoo station. I checked a couple of the services powering railroad signal boxes here... yes, proper three phase delta powered by three tub transformers.... simple configuration.

Anyway, driving in the entrance of the bridge park, the drive pulls under this beauty bridge... the #6 bridge per the map with the bridges numbered.

I am thankful,
Michael Lueck

 

[CoolWill]

It certainly looks like straight 240 with one leg grounded, like a European system. For some reason they wanted a line to ground voltage of 240.

 

[mdlueck]

It certainly looks like straight 240 with one leg grounded, like a European system. For some reason they wanted a line to ground voltage of 240.

And the USA is purchasing crossing signaling equipment from Siemens! haha

I am thankful,
Michael Lueck

 

[tortuga]

Thats a neat photo thanks for sharing, its probably the only photo of a 'single phase' utility service on this forum. Its cool to see photos of all the unconventional systems still in use.
Not sure what is gained by single phase vs split phase, probably at one time it was a true 240 transformer or even a 240/480 split phase and the POCO replaced it with a standard inventory 25kVA.
My guess is that is not a rail signal service rather for a pump of some sort, perhaps park irrigation.

 

[Hv&Lv]

Single phase straight 240 transformer. No center tap, so no 120V available.

 

[Tulsa Electrician]

I think the sticker on the meter enclosure says 5 wire 2 phase. If so how cool

 

[Tulsa Electrician]

Could be why it's 240 volt single phase now.

 

[mdlueck]

I think the sticker on the meter enclosure says 5 wire 2 phase. If so how cool

Nay.... "3-Wire 3-Phase Delta Service and Metering"

You remind me of one of my usual counter representatives when I was a teenager.... I needed a 30 amp 2-pole circuit breaker. In haste I asked for a "30 2-pole" which he put on a show of trying to literally turn on a "32-pole" breaker. (Just think of trying to get correctly wired a 32-phase motor!)

My point was how does 2-Wire equate to a Delta Service of any type.

OK, "two insulated wires connected to the transformer..." never mind the fact that one of the two insulated wires is also connected to ground.

Possibly with the digital delta electric meter it has intelligence to not care that all three conductors are actually connected.

I am thankful,
Michael Lueck

 

[Hv&Lv]

Nay.... "3-Wire 3-Phase Delta Service and Metering"

You remind me of one of my usual counter representatives when I was a teenager.... I needed a 30 amp 2-pole circuit breaker. In haste I asked for a "30 2-pole" which he put on a show of trying to literally turn on a "32-pole" breaker. (Just think of trying to get correctly wired a 32-phase motor!)

My point was how does 2-Wire equate to a Delta Service of any type.

OK, "two insulated wires connected to the transformer..." never mind the fact that one of the two insulated wires is also connected to ground.

Possibly with the digital delta electric meter it has intelligence to not care that all three conductors are actually connected.

I am thankful,
Michael Lueck

Sticker is wrong

 

[tortuga]

Looking at it on google street view it sure does look like its for the rail line:

Street View · Google Maps

Explore a place in a more immersive way in Google Maps.

maps.app.goo.gl

Sticker is wrong

Perhaps there is a limitation with a 'standard' split phase meter like our slash rated breakers that they can only handle 120V to ground? So for a 240V service single phase a 240 'delta' meter is needed?

Whats odd is then they have a 5kVA 120V transformer, perhaps its a recent addition? But why not just connect the utility neutral? I guess the only reason would be 240V continues on down the rail line and it has one line grounded along the line or even uses a 'rail' as a the grounded conductor. Essentially what they are using is the equivalent of end grounded split phase service

 

[OldBroadcastTech]

it's probably an old sticker. RR's are notorious for never throwing anything away if it can someday be re-used.

 

[tortuga]

I think its something like this:

Which could be accomplished like this:

 

[zbang]

I'd call that uncommon (and unlikely); using a track return would potentially mess with older track circuits and there's a signal right there. @tortuga what's the source for those drawings? I'd like to take a closer look.

 

[tortuga]

I'd call that uncommon (and unlikely); using a track return would potentially mess with older track circuits and there's a signal right there. @tortuga what's the source for those drawings? I'd like to take a closer look.

Oh thats just me messing around with a old control drawing of mine that used a similar setup, a end grounded transformer, I was just speculating on what the advantage would be of 240V end grounded? Presumably it is the signal.

 

[jaggedben]

If the service is actually for the railroad my guess would be it has more to do with the nearby grade crossing arms and lights than for signals for trains. Agree with zbang that they would not put 60hz AC power directly on the track.