3 phase to single phase supply

[nagasahitya]

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]

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.

 

[gar]

1605218-0928 EDT

A motor generator, or rectify to DC and from DC synthesize a single phase sine wave (or an approximate sine wave).

.

 

[ron]

Rotary phase converter, although it would be custom in that application voltage.

 

[ggunn]

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

Using just transformers, I mean.

 

[Ingenieur]

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

 

[Phil Corso]

GGunn...

How about an AC-DC converter, similar to the front-end of a VFD!

Phil Corso

 

[electrofelon]

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

I have heard there is such a connection. Perhaps
Considering that a Y-D or D-Y transformer results in a 30 degree phase shift, would it not be theoretically possible to have such an arrangement?

 

[GoldDigger]

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]

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

 

[LMAO]

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]

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]

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]

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.

 

[Ingenieur]

I only remember some unsubstantiated claims that it is possible.

I saw the same posts (here and elsewhere)
when you phasor summed his sec it equaled 0 lol

 

[gar]

160518-1548 EDT

Ingenieur:

The phasors in phase with A to N are each 120 V and thus three voltages of the same value, current, and phase angle are each the same real power value.

The 90 degree phasors are each 207 V and and 180 degrees apart and cancel each other.

If you look into the reference you provided and further references there you will see drawings and descriptions.

https://dl.dropboxusercontent.com/u/88752751/Transformer for 120-240V from 3-phase - Detailed A2.doc

.

 

[don_resqcapt19]

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]

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.

Best me to it :rant: FWIW its mentioned at the end of this paper linked in this thread posted earlier:


http://forums.mikeholt.com/showthread.php?t=146298&p=1411181#post1411181

 

[mbrooke]

SO, I have always wanted to ask. If put a current oscilloscope in the primary, what would it look like? :?

 

[GoldDigger]

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.