Can someone please explain the difference between Single Phase 230v and 2 Phase 230v

I am looking at a machine that is at a plant here that says 230v 2-phase.

Don't know if that will run on single phase 230v and if not what I would need to run 2-phase 230v.

I'm no electrician but I think standard residential 230 volt is 2 phase at a 90 degree phase angle
230 volt single phase or 230 volts on a single hotline would be difficult to get in a residential situation without a Transformer

I am not a US rare electrical grid expert by any means, but..

I think I have read somewhere that 2-phase power in the US was used, very rare, in some places.

In most of the rest-of-world,...
power that is single phase is == 220V (== 240V, +/-).
No hot/neutral etc. The lines are equal.
A safety ground, not in use normally, and a brown/blue color for the power lines, most commonly, both carrying the 220V single phase.
Connectors not keyed- since you can invert the plug or swap the lines and everything works just the same.

Then, most 3-phase is 220-240V (less common/rare) or 380V (400V, same thing).
3 equal lines, plus safety ground, total 4.
Safety gnd is green/yellow, mostly, today(s).

2-phase power ? Whats that ?
Moral of story, I think.
Are you really in an area that has ever had 2-phase power ?

I would suspect its either single phase 220V or 3-phase 220, and thus...
the 3-phase would have 4 wires, and the single phase, US, might have 3 ?

I think the US 220 would then be line-hot-neutral in us terminology ?? or not ??
My first thought would be poor markings.

Since You say plant, I hear "big power" ie 25-40 kW and up, and thus I would never ever do a "smoke test".

Otoh, depending on motor, a lot of 3-phase motors can run on tiny current no-load.
Like 0.1 kW, or 100W, or 50 watts.

If you have a fast gfi, and a spare line, it might be possible to test it, cheaply.
Please dont do this from the main panel of a big industrial plant ..
you probably don´t want to trip the whole plant supply by surprise, when running industrial processes.
Likely (depending) to cost more than a new 40kW motor...

Grin

Interesting Question, for sure.

You did not mention power levels or data, or data from plant, but castings or transporters or process-lines generally don´t like the power shutting off unexpectedly.

Whats your goal and budget ?
If you just wanna get it running, a cheap rented 1-day genset, and try it, might be best or good enough, depending on power levels.
Ie if its a 1MW thingy, that might change things.

If it´s not-usable as-is, often it´s more trouble than it´s worth to fix it, unless someone already knows how and has done so umpteen times.

In my old biz, the top techs were very good, and would connect a 50 kW line, hot, into machines.
Note hot.
Line by line, all 4, while energised.
I would never, ever, do that, myself.
Just not brave enough.

2 phase is still being supplied to customers in parts of Phila, Pa. If you buy that machine your either going to use transformers or replace the motor. I seen a clean Bridgeport a dozen years ago at a auction go cheap because it was wired for 2 phase.

2 phase does exist- its still in use in Philly, some of Hartford CT, and a few spots in upstate NY.
And so there are machines that use 2 phase motors.
The motors wont switch to single or 3 phase- if its really is a 2 phase machine, and you dont have 2 phase, you would probably need a new motor.
I think you can stepdown, with a transformer, from 3 phase. I dont think there is a way to step up from single phase, but I could be wrong.

but sometimes people who are not real conversant in electricity call something "2 phase" that isnt.

Two-phase electric power - Wikipedia

Single phase is what is used in residential power. That means just two wires. The three wires that are brought in are still single phase, two hot lead and a ground. The two hot leads are really the same, The difference is that, at the transformer feeding the house, the high voltage winding has been center tapped so as to provide 115/230 service. One hot lead to ground (or common) is 115, while one hot lead to the other is 230. The common is not needed in the second case. A fourth wire is the safety ground and is independent of the other wires.

Two phase power was developed in the late 1890's for self starting electric motors. Single phase cannot start a motor without start winding's. Two phase (and 3 phase) are generated with two (three) completely separate winding's in the generator. These are separated by 90 (120) degrees. It should be noted that once a single phase motor is started, it works quite well on single phase. The same is true with a poly phase motor.

The polyphase motor is just like the generator, it has multiple sets of winding, either two or three. When the motor is energized, the current in one winding will be rising to a maximum and then will decline. During the declining in the first winding, the current the second winding will be rising. If you were sitting on the rotor while this happening and had compass, it would appear the the magnetic flux is moving from the first winding to the second winding, and in fact that is exactly what is happening. This moving magnetic flux also happens between the second the third winding and then between the third and the first winding. The result that for a complete electrical cycle the magnetic flux vector in the rotor has now moved a full 360*. The rotor will move to follow this cycle.

Why did two phase for all purposes disappear? It takes four wires for two phase but only three wires for 3 phase. Its economics. Some areas of the country still have two phase power, mainly in Philadelphia.

Tom

paracongo308 said:

2 phase is still being supplied to customers in parts of Phila, Pa. If you buy that machine your either going to use transformers or replace the motor. I seen a clean Bridgeport a dozen years ago at a auction go cheap because it was wired for 2 phase.

Click to expand...

You can produce two phase power from three phase using a Scott connection transformer. Otherwise connect a single phase motor to a two phase generator if you can find one.

Tom

while one hot lead to the other is 230.
Tom[/QUOTE]
Isn't this the result is a phase difference

Spud said:

I am looking at a machine that is at a plant here that says 230v 2-phase.

Don't know if that will run on single phase 230v and if not what I would need to run 2-phase 230v.

Click to expand...

Recall what I said about running a polyphase motor on single phase? Connect the 230 volt line to one of the phases. Connect a starting capacitor through a relay, timer or switch to one of the other motor leads. Connect the remaining wire to one of the first leads. Now you have a self starting motor. You can even go further and make the second winding both a start and run winding by a combination of a starting circuit using a timer and capacitor in parallel with a run capacitor.

Tom

Hbjj said:

while one hot lead to the other is 230.
Tom

Click to expand...

Isn't this the result is a phase difference[/QUOTE]

Nope, comes from one winding of a transformer. Think of a Variac variable voltage transformer. connect a volt meter or scope to one end of the variac and the second to the wiper. When the wiper is a zero volts, everybody is in phase, right? Now slowly turn to variac to maximum. The voltage is 230 or 120 or whatever, but the phase is still single. There was not a magic spot where there phase changed.

Tom

We want to see a pic of the motor nameplate. Or the machine plate if motor is not accessible, preferably both.

Not that we do not believe you, but many details may be cleared up by seeing it.

Oh, yeah, if the machine and/or motor are not pretty old, the odds of it really being 2 phase go down considerably. I doubt any but specialty motors (if any) have been made in 2 phase for decades.

TDegenhart said:

Recall what I said about running a polyphase motor on single phase? Connect the 230 volt line to one of the phases. Connect a starting capacitor through a relay, timer or switch to one of the other motor leads. Connect the remaining wire to one of the first leads. Now you have a self starting motor. You can even go further and make the second winding both a start and run winding by a combination of a starting circuit using a timer and capacitor in parallel with a run capacitor.

Tom

Click to expand...

Yes, lots of folks make 2 phase and don;t know it.... They have 2-capacitor motors..... one start , one run. Or PSC motors, where one cap does both.

Spud said:

I am looking at a machine that is at a plant here that says 230v 2-phase.

Click to expand...

Instead of speculating, is it possible to provide photos of the machine tags. It's possible that the person that labeled it could of been mistaken. Seems highly unlikely in your location, your local grid would actually be 2Φ supply. Was it connected in a plant? What does the service equipment in the building say? Is the other equipment 2Φ ?

Motor nameplates would be ideal. How many line wires supply the disconnect on the machine? 2,3,4W ? Did it have a Scott T transformer to convert from 3W 3Φ to 4W 2Φ?

Many people think of a 2 wire 230V supply as 2 Phase 230V. When in reality it is actually 2W 1Φ 230V.

More information would be helpful.

SAF Ω

TDegenhart said:

Isn't this the result is a phase difference

Click to expand...

Nope, comes from one winding of a transformer. Think of a Variac variable voltage transformer. connect a volt meter or scope to one end of the variac and the second to the wiper. When the wiper is a zero volts, everybody is in phase, right? Now slowly turn to variac to maximum. The voltage is 230 or 120 or whatever, but the phase is still single. There was not a magic spot where there phase changed.

Tom[/QUOTE]

so you're saying there's no phase difference in residential 230 volt power if that's so then why are there two bus bars in my panel instead of one and how can I run a 3-phase motor happily albeit at 2/3 power on single phase residential power

Hbjj said:

why are there two bus bars in my panel instead of one

Click to expand...

The 2 bus bars are a connections(lines) to the end connections of a single transformer winding. The winding IS the "phase", the wires or bus bars are the "line"

how can I run a 3-phase motor happily albeit at 2/3 power on single phase residential power

Click to expand...

When you run 3Φ motors on 1Φ. You supply 1 phase through 2 wires, and energize one phase winding of 3 windings inside the motor. Effectively internally generating the other TWO phase (winding) voltages. However externally your only measuring one LINE voltage generated.

There is a distinction between LINE and PHASE. Line is the external connection. Phase is the voltage developed across the winding. They are different.

SAF Ω

SAF said:

The 2 bus bars are a connections(lines) to the end connections of a single transformer winding. The winding IS the "phase", the wires or bus bars are the "line"



When you run 3Φ motors on 1Φ. You supply 1 phase through 2 wires, and energize one phase winding of 3 windings inside the motor. Effectively internally generating the other TWO phase (winding) voltages. However externally your only measuring one LINE voltage generated.

There is a distinction between LINE and PHASE. Line is the external connection. Phase is the voltage developed across the winding. They are different.

SAF Ω

Click to expand...

That's true if the motor is delta wired. For wye, which are most of the motors I have seen, two phase windings are energized.

Residential power is actually split single phase. One line from a high voltage 3 phase grid goes to one end of a fine coil of wire around an iron core, the other end of the coil goes to ground. A heavy coil of wire is the low voltage side of the transformer. One end of the coil is one of your "hot" legs and the other end is your other "hot" lead. In the center of the low voltage coil of wire another wire is attached, effectually making two coils, that wire is your "neutral", which also goes to ground. That way current will flow between the ends of the coil giving 240 V or between one end and the center giving 120 V. You can think of single phase as just one loop of wire going to the generator and back to your load. Three phase is like having three different loops of wires with each loops 120 degrees apart from the others.

A lot of this confusion is semantic unfortunately. Here in the US, we have TRUE 2-phase power, as mentioned still used in Philly and a few other small pockets of old cities. Tesla's first polyphase AC generator at Niagara Falls was 2-phase and was still in use until recently (might still be in the museum I've heard). So for us, the term "2-phase" has a SPECIFIC meaning.

In the REST of the world they have only one distribution system, it is always 3-phase, and almost always Wye, so it is 400V phase-to-phase, 230V phase-to-neutral. That 230V phase to neutral is what they call "1-phase", defined as one hot + 1 neutral. If they connect something line-to-line, but is is 400V, they call that "2-phase", which really means "2 out of 3" phase.

But when they (in particular, Germans) sell a piece of machinery going to the US, they look at our "3-phase 230V" distribution and see that if you want to connect a single phase motor, both lines are hot, which for them is what THEY call "2-phase". And for them, the concept of a "single split phase" is total nonsense, so they stick to what they understand. That frequently makes it onto motor nameplates. Side note: Brits don't usually have this problem, because they too have split-phase distribution in some areas, so you don't see that "2-phase" wording used. It's mostly Germans, French, Italians, Swedes, countries like that.

I've spent 11 years of my career working for German electrical equipment manufacturers, I can attest to how confused they are over there about our systems. But because from their viewpoint, we are less than 2% of their worldwide market (they never ceased rubbing that in to us), they don't bother trying to learn, they just expect us to figure it out.

JST said:

Oh, yeah, if the machine and/or motor are not pretty old, the odds of it really being 2 phase go down considerably. I doubt any but specialty motors (if any) have been made in 2 phase for decades.

Click to expand...

Back when I did that sort of work, I used a lot of 2 phase motors, mostly 400 cycle. They were servo systems with a error signal from a bridge like a Wheatstons bridge but run on AC. One winding on the motor and the bridge were fed AC 90 degrees apart. The bridge output went to what amounted to an audio amplifier which energized the second winding. When the bridge went from unbalance one way through zero and to unbalance the other way, the motor reversed and corrected the error. Of course, a RADAR mortar locator is probably a specialized application.

Bill

That motor nameplate is kinda important to get to the bottom of this.

Tom

1+1=3?

jraef is getting to the hart of the confusion I think. yes largely semantics, so why not just post some schematics of the secondary winding config of the different systems? one pic worth a th...

yes, I would do it my self, but have to get to work, make the dollar, keep the lights on...

I'll leave you with this little conundrum.. if 2 poles of 3 phase is still single phase 240, how is it that when you add one more pole it becomes 3 phase? 1+1=3?