Open circuit test of 3 phase transformer in Ansys Maxwell

[GauravU]

Hi all,
I am designing a three phase 11000/433 Volts Delta/Star 50 Hertz transformer in Ansys Maxwell. It has 792 turns in 6 layers on HV side (132 turns per layer) and 18 turns in 2 layers (9 turns per layer). The resistance as I have calculated is 0.1325 ohms per phase of HV winding and 5.57 micro ohms per phase of LV winding. I have done all the modelling and doing transient type simulation but I am facing certain problems as the results are not as per my expectation:

1) What should I put in the number of parallel branches and number of conductors?
(132 conductors and 6 parallel branches or 792 conductors and 1 branch). The conductors are wrapped around just like a winding so I think all are connected in series

2) How do I conduct the open circuit test on the transformer?
I have used 2 approaches:
(i) I deleted the HV winding in the model and supplied the full voltage to LV winding as HV has to be kept open. Is that the right approach? I am doubtful as it will cause full load current of LV to flow, so that won't comprise an open circuit test as to my knowledge.

(ii) I designed a circuit in Maxwell Circuit Editor containing both the windings but I am unable to get how to keep the HV winding open. When I keep the HV winding inactive(open) and export the netlist, Maxwell gives error during simulation (not while importing netlist) that windings of HV are not there in the imported circuit. When I simply keep the HV circuit open, still Maxwell gives error. As you can understand, I can't connect ground on the HV side as it is open circuit, so how should I do it?

3) I wish to know what are the typical values of Kh, Kc of a transformer of such rating. Frequency=50 Hertz Material density=7650, thickness= 0.27mm, conductivity= 5000000S/m. The values I am getting are Kh=65.489 and Kc=0.599. Are they good enough or typical values are not in this range?

Project4.zip contains the full load circuit

Project6.zip contains the open circuit test circuit

Please do let me know if there is some fault in my design

 

[Nick_page]

Is there way to address this? I think Maxwell doesn't converge if one of the windings is left unexcited

 

[Tom.G]

By leaving a winding un-connected you have a floating inductor. Simulation software doesn't like disconnected components, it can't create the network equations to calculate a solution. The usual fix is to put a high value resistor across the component. At least some solvers also require a path to circuit common (Ground).

Cheers,
Tom

 

[essenmein]

I've never actually simulated a transformer, mostly just machines, but really they are basically a transformer where the secondary winding is a rotor, the way I usually handle open circuit voltage simulation to determine d/q harmonics etc is by placing a current excitation with 0A, then run. You should then be able to plot the voltage the current source has to apply to maintain zero current.

 

[essenmein]

holy resurrected thread...