2 phase power supply Meaning?

[Michael2009]

Hi Friend,

Client power system is IT system
for 220V AC utilities supply they put 2 phase supply in 2 wire L - L.
So my instrument, lighting, everything is single phase L N E connection.

So can i direct wire supply L - L to L - N terminal? or i need a transformer for between the supply and my instrument?

Thanks.

 

[Compositepro]

You should mention that you are in Japan. Also, when you say 2-phase, I believe you actually mean "split-phase", which is derived from a single phase transformer with a center tap. I will let others answer further, since it appears that Japanese wiring standards are varied, and I have no familiarity with them.

 

[Michael2009]

You should mention that you are in Japan. Also, when you say 2-phase, I believe you actually mean "split-phase", which is derived from a single phase transformer with a center tap. I will let others answer further, since it appears that Japanese wiring standards are varied, and I have no familiarity with them.]

I not in japan.. just a project spec.

I think i will rephrase a bit my question.
Client supply two phase power L1 and L2 (2-wire) to my instrument. Can i connect L1 to L and L2 to N in my instrument?

 

[itsmoked]

With the information given.. I'm sorry no.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Hard to get two phases on only two wires.
I believe that we have a terminology misunderstanding.
You have not told us the voltage rating of your equipment.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

Two phases of a 3-phase system does not become a 2-phase system, rather it is one of 3 or 6 ways of getting single phase from the 3-phase system. In a three-phase system there is some point, real or conceivable, that can be a reference to three different conductors all at 120 degrees to each other. In a single phase system you have two conductors and 180 degrees between them; can be phase-neutral in a wye system or phase-phase. In a two phase system you have somewhere between 3 and 5 conductors and can readily discern two phases that are 90 degrees to each other. Two-phase is old, obsolete, and talked about far more often than it is actually spotted in the wild. If you start with a three-phase system you can't get to a two-phase system without a special transformer.

 

[daveross100]

FYI: In the USA here in NYC, only 2 phase 100A - 110Vac =~ 20KW are supply to every house by Con Edison , the two phase has 180 Degree different ,

it used as 110Vac two sources of 100A [ common grounded ] ,and / or a source of 220Vac the two sources in series , the source has 3 lines L-110Vac Zero degrees ,Center N ground for the 110Vac supply and L-110Vac 180 Degrees,

Connection between L110Vac Zero Degree and the L110Vac 180 Degree, of the supply made for big 220Vac loads like cooking stoves or dryers, A/C ect, the two "series phases" are used and supply the 220VAC , each of the lines can be connected to the L and N of a "normal" 220VAC load ( who cares that the middle=Center is connected to ground ? )

Important: the supply lines to the L 220 and N 220 of the load shall have 2 breakers and the on/off knobs of the TWO are
"connected together" = "common knob" A MUST !

 

[daveross100]

NO NEED OF TRANSFORMERS !

 

[crshears]

Hi daveross100, you seem to be describing what compositepro calls "split phase" in above post...

I agree with davidbeach's post, as I've only ever seen true 2-phase power, meaning 2 phases @ 90° displacement, described in old pre-WW2 technical books; I've never ever seen it in use.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Mbrooke]

@Daveross: Consolidated Edison hasn't supplied 110 and 220 volts nominal for over 60 years. 2 phase is 90* apart, not 180 which is split phase.

 

[waross]

Many apartments in North America are fed with two phase power. This is two phases of a three phase supply. 120 and 208 Volts.
The 120 Volt phases are 120 degrees displaced. The nominal 240 Volt heating elements in electric ranges, clothes driers and hot water heaters are a little slower to heat but no one notices.
I have heard rumors that at one time some large cities used an underground 120:208 Volt grid in downtown areas and supplied small users with two phases. Can anyone support this?
I lived in such an apartment. The apartment manager was a retired industrial electrician. He was unaware that his apartment was supplied with two phases. He had thought that his apartment had the traditional 120:240 supply.
The main service is three phase, 120:208 Volts but only two phases are supplied to each apartment.
But 120:240 Volts two phase? That is a center tapped 240 Volt supply. Split phase is a type of motor.
Interestingly, two phase may be argued to be used internally in a "T" winding or Scott transformer to transform three phase power.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[stevenal]

Waross,

Two phase power is defined by IEEE, and it does not involve angular differences of either 180 or 120 degrees. See Crshears' post above and faq238-777.

 

[waross]

Nice FAQ stevenal.
I agree in regards to 180 degrees not being two phase.
My suggestion of two of three phases being called two phase was mostly in opposition to those who persist in calling 120:240 two phase.
I note that IEEE does not address two of three phases.
It is common and it is not single phase. It does produce a rotating field. Open wye? Not common usage.
I pretty well agree with your FAQ.
I am willing to try to remember to call the apartment feeds "Two of Three Phase".

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[stevenal]

Thanks. Don't forget to vote.

IEEE may not address two out of three, but NEMA does in the metering standards since we must meter them properly.

For those not familiar: An apartment building with a swimming pool is to be served. A wye secondary transformer might be chosen to provide 3 phase to the pool pump motors and open wye services to the individual apartments balanced over the three phases. Heating loads work fine at 208, they just take longer to reach the set point. Just make sure the electrician installs 5 lug meter bases.

 

[crshears]

Most if not all of the generating and transforming stations where I worked in the past and even the grid control centre where I work now all all have 2/3 phase power @ 120/208 into the operator's kitchens, & we sure notice how long it takes to get a pot of water to a boil for cooking pasta or corn on the cob; our typical office/control building power supply other than for HVAC loads etc. is 120/208 wye, and the company has never to my knowledge sprung for the added cost of proving proper 120/240 split-phase power for the kitchen facilities. You really have to get started early when cooking up a feast on a holiday weekend...if not, the next shift will end up eating your food.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

I had a customer who sold two phases (120/208V) to fishing boats when they were alongside the wharf.
His boys installed a standard single phase revenue meter.
It was accurate for 208 Volt loads but the meter assumed that the 120 Volt loads were 104 Volts and registered only 104/120 = 86.7% of the 120 Volt loads.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

Did it save/cost anyone any money?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

I avoided getting involved with the rate structure.
For one kilo-Watt-hour used at 120 Volts the revenue meter would indicate 0.867 kilo-Watt-hour used.
They were probably overcharging but weren't making as much profit as they thought.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[stevenal]

Blondel had it right.

Customer saved a bit on meter and base and installation. Boat owners saved, with the customer making up the difference.

 

[crshears]

Only if the marina / boatyard owner does a direct pass-through to the vessel owner of perceived energy cost and doesn't just bloat the bill by marking up the power cost by 200% or something like that, in just the way I've seen marina owners charge an exorbitant price for gasoline / Diesel fuel...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]