SPICE transformer model question

[understress]

I am currently trying to implement a SPICE model (for use in ISIS) of a transformer I use in my designs.

The transformer has a delta wired primary, and two secondaries. The first secondary is delta wired, and the second secondary is wired as a wye. I know from measurements taken on the transformer that there is a 30 degree phase shift between the two secondaries.

Conceptually I have a schematic sketched out to represent the transformer in SPICE. I have a resistor for each coil to represent coil resistance, and an extra inductor for each coil to represent leakage inductance.

I know I need to set the coupling factor, but I do not know how to inform SPICE that there is a 30 degree phase shift between the 2 secondaries. Or will SPICE know this because of the inductor model?

I have tried some Google searches on this but have not come up with anything yet that helps me. If anyone has experience with this and can help out, or point me to web page with some information regarding this, I would be very grateful.

Thanks,

Scott

[Ettore]

I think the delta/star or star/delta as well - delta/wye is a theminology used by pretty north american people - configuration of three phase results in a 30 degree phase shift between the primary and secondary line-to-line voltages not between secondaries. I must have somewhere a monography explaining in deep details how those transformers work given your math is reasonably good. If I find it then I will PM it to you (I have downloaded it from the net though, if memory serves).

It's the inductors configuration that sets the phase shift, you don't have to tell SPICE with any information about that.

Attached find a simple model with no leakage inductance however. The mutual coefficient is less than 1.0 that would model the leakage.

[understress]

Ettore,

Thanks for the quick reply. I'm not concerned about phase shift from primary to secondary. I'm only concerned about the phase shift (or difference) between the two secondaries. There IS a phase difference between my two secondaries, I've confirmed it with an o'scope.

My company does not specify the exact requirements of how the transformer is designed, we only specify that it must meet certain requirements (ie: input voltages, output voltages, output currents, duty cycle, etc). We rely on our transformer manufacturer to be the experts for the design details. I am the only engineer at my company and do not have expertise in transformer design. Although in the last couple of weeks I've learned quite a bit about how transformers work (beyond the basics), and learned things like it is possible to have 2 secondaries on the same transformer and have them not be in phase with each other. My first thoughts about that agreed with you, that they should be in phase, but I have since found out that it's possible for them not to be. I suppose it is because on secondary is a delta winding, and the other secondary is a wye (star) winding.

Any further help is greatly appreciated, thanks,

Scott

[understress]

Ettore,

I have built a 3 phase transformer using the suggested method you used in your example and have found that the SPICE engine automatically seems to account for the required phase shift between secondaries.

But, I do have one question: My inductor symbol from the libraries does not have the phasing dot on the symbol, and also has '{PINSWAP=1,2}' as one of its properties. Which inductor did you use? Or is it a custom part you created? I can create my own part if that is what is required, but if the part is normally included with Proteus, I'd rather use that part.

Thanks,

Scott

[Ettore]

I'm delighted to know you've finally got my suggestion

The inductor I have used is in the standard library to: Modelling Primitives=>Analog (SPICE)=>INDUCTOR
However even those under the Inductor library will do: SPICE for definition assigns the pin 1 to the phase dot.