Six phase

[ohmhead]

Well today we hooked up a high voltage rectifier with a six phase output transformer, for equipment now on site . The taps & connections there were one common feeder to two transformer primary each three phase ABC wye and one ABC delta primarys the secondarys were factory wired to rectifier and equipment a one time connection . Question is how do they get phase shift to give six phases in rotation and at what degree of shift ? Is this like our standard three phase or is this just a rectified six phase dc pulse ? comments take care best to yas

 

[charlie b]

I've never dealt with such things. But I am presupposed to guess that 360 divided by 6 is 60, from which I infer that each of the six phases is 60 degrees apart from its neighbor. :roll:

 

[LarryFine]

Question is how do they get phase shift to give six phases in rotation and at what degree of shift ? Is this like our standard three phase or is this just a rectified six phase dc pulse ?

Take a 3ph transformer, using center-tapped secondaries. Connect the three center taps together, forming a neutral.

You now have six hot wires to rectify, making an easier DC voltage to filter and smooth.

 

[jim dungar]

Given identical primary connections, there is a 30? phase shift between a delta and a wye secondary. So if the wye voltage angles are 0, 120, and 240 the delta ones could be 30, 150, and 270.

 

[Besoeker]

Take a 3ph transformer, using center-tapped secondaries. Connect the three center taps together, forming a neutral.

You now have six hot wires to rectify, making an easier DC voltage to filter and smooth.

That's sometimes called hexaphase and it gives you the same as a full-wave rectifier bridge with a three-phase input - 6-pulse.

Another arrangement is for the transformer to have a star and a delta secondary (Ddyn0) and feed two rectifier bridges which are connected via an IPT. This provides 12-pulse. One of the main reasons for doing that is to get reduced harmonic currents in the supply.

 

[ohmhead]

Well the transformers are one = delta delta & one= wye wye after looking further into this we opened up equipment to learn more about six phase and how this connection is made .we also see a neutral internal to and used for control power its interesting to us to understand the process of polyphase thanks for the input .We might read the manual on this piece to get a better look at how its wired we do alot of odd projects and always like to learn more about what we work on never can learn enough ? comments take care

 

[physis]

Given identical primary connections, there is a 30? phase shift between a delta and a wye secondary.

Is that true? like you'd change your mind because I asked that. :grin: I'm gonna have to give this some thought.

 

[winnie]

Is that true? like you'd change your mind because I asked that. :grin: I'm gonna have to give this some thought.

Yup, its true. Consider 1:1 transformers and compare input to output.

A delta-delta transformer has output that is in phase with the input.

A delta-wye transformer has output that is shifted 30 degrees relative to the input.

-Jon

 

[dbuckley]

Is that true?

Its absolutely true.

Again, its one of the core concepts of how HVDC converter stations work, they use a pair of transformers, one wye, one delta.

Image from here.

 

[broadgage]

Here in the UK 6 phase transformers are used to supply rectifiers for electric railways.
Some railways supply 750 volts DC to the train via a conductor rail.

The transformers have a standard 3 phase HV primary winding and a 6 phase medium voltage secondary.
Two designs of winding exist.
1) each limb of the core has one winding on it, each with a center tap, all three center taps are connected together, and all six winding ends are brought out to connect to the rectifier.

2)Each limb of the core has two windings on it, wound in oposite directions. The bottom six ends are all joined together, and the other six are connected to the rectifier.

It will be noted that the two arrangements are electricly identical, it is simply a choice as to which style is easier to manufacture.

Six phase transformers rated at hundreds or even thousands of amps, at only a few volts used to be used with a rectifier to supply electro plating works.