3 phase to single phase supply

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nagasahitya

New member
Location
India
Hiii ,

I require a single phase ac supply in my LAB with volatge rating (1000 V)rms ,current rating 600 A. 3 phase 415v supply is available in my LAB.please tell me the best methods to convert my 3 phase supply in to single phase.Important thing is i must maintain balanced load on the 3 phase side.


Regards
sahitya
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
Hiii ,

I require a single phase ac supply in my LAB with volatge rating (1000 V)rms ,current rating 600 A. 3 phase 415v supply is available in my LAB.please tell me the best methods to convert my 3 phase supply in to single phase.Important thing is i must maintain balanced load on the 3 phase side.


Regards
sahitya
There is no way that I know of to make single phase from three phase using all three phases.
 

Ingenieur

Senior Member
Location
Earth
1000 VAC x 600 A = 600 kva
input at 415/3 is 835 A

600 kva 415:1000 3 ph xfmr
feeding a 1000 VAC 1000+ HP VFD (expensive VFD lol), 1000 vac is a common mining voltage and drives are available
use two phase legs of the output
input will be balanced since rectified to a DC bus
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Just such a transformer connection has been described in a thread here. It produces single phase drawing equally from all three source phase lines.
 

Ingenieur

Senior Member
Location
Earth
the common way with xfmrs is a 2 winding primary open delta and a 2 series winding secondary
but it is not balanced
2 phases are equal, the third is 1/2 the load iirc

I'd like to see how it is done balanced
3 phase primary coupled to a single sec coil?

here's the post that purports to get 3 ph-1 ph balanced operation no drawings or real info though http://forums.mikeholt.com/showthread.php?t=146298
 
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LMAO

Senior Member
Location
Texas
use the 3 phase to feed a VFD with a sinewave filter at it output because VFD output is not sinusoidal. Needless to say, it is not straightforward, you need professional engineers to do all the design.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
160518-1319 EDT

A transformer method is based on the mathematical identity that the sum of multiple sine waves of identical frequency and phase locked together produces a single sine wave of the same frequency, and some phase angle.

If A to N is 120 V, B to N is 240 V, and C to N is 240 V, then by properly connecting these secondaries in series, they are not joined at a neutral point, the summed voltage is 240 V and in phase with A to N The real power loading on each transformer is the same. Thus, a balanced real power load is presented to the source.

.
 

Ingenieur

Senior Member
Location
Earth
160518-1319 EDT

A transformer method is based on the mathematical identity that the sum of multiple sine waves of identical frequency and phase locked together produces a single sine wave of the same frequency, and some phase angle.

If A to N is 120 V, B to N is 240 V, and C to N is 240 V, then by properly connecting these secondaries in series, they are not joined at a neutral point, the summed voltage is 240 V and in phase with A to N The real power loading on each transformer is the same. Thus, a balanced real power load is presented to the source.

.

3 sec coils
ph A 120/0
ph B 240/120
ph C 240/-120

series connected

how are the 'dots' oriented?
A and B the same, C opposite?
all the same?
etc

if in series all carry the same current, correct?
but if the V is different (120 and 240) the power must be different per coil?
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
Just such a transformer connection has been described in a thread here. It produces single phase drawing equally from all three source phase lines.
I only remember some unsubstantiated claims that it is possible.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
It would be the same connection that you use on a 12 lead generator....a double delta or a zig zag connection of the secondary side, however you would need the secondary side of each of the 3 transformers to have all 4 leads brought out.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
the common way with xfmrs is a 2 winding primary open delta and a 2 series winding secondary
but it is not balanced
2 phases are equal, the third is 1/2 the load iirc

I'd like to see how it is done balanced
3 phase primary coupled to a single sec coil?

here's the post that purports to get 3 ph-1 ph balanced operation no drawings or real info though http://forums.mikeholt.com/showthread.php?t=146298

It is not a simple as three primaries and one secondary.
Basically you interwire three individual secondary windings in a complicated way. It is similar to the complicated interconnection of the Scott T circuit between two phase and three phase.
 
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