Open circuit test of 3 phase transformer in Ansys Maxwell

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Discussion Overview

The discussion revolves around the simulation of a three-phase transformer using Ansys Maxwell, specifically focusing on the open circuit test. Participants are addressing issues related to modeling, simulation setup, and the interpretation of results in the context of transformer design and testing.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes the transformer design parameters, including turns, resistance, and simulation type, and expresses concerns about unexpected results.
  • Questions are raised about the correct configuration for parallel branches and conductors in the simulation, with uncertainty about whether to use 132 conductors with 6 branches or 792 conductors with 1 branch.
  • Concerns are expressed regarding the methodology for conducting the open circuit test, particularly whether deleting the HV winding and supplying voltage to the LV winding is appropriate.
  • Another participant suggests that leaving a winding unexcited may lead to convergence issues in Maxwell, indicating that disconnected components can cause problems in simulation.
  • A suggestion is made to place a high-value resistor across the disconnected winding to help the simulation software create the necessary network equations.
  • Another participant proposes using a current excitation with 0A to simulate open circuit conditions, allowing for the plotting of voltage without current flow.
  • One participant inquires about typical values for Kh and Kc for the specified transformer rating and shares their calculated values, seeking validation.

Areas of Agreement / Disagreement

Participants express differing views on the proper approach to simulate the open circuit test, with no consensus on the best method to handle unexcited windings or the validity of the proposed values for Kh and Kc.

Contextual Notes

Limitations in the discussion include unresolved issues regarding the simulation setup, the handling of disconnected components, and the interpretation of transformer parameters. There is also uncertainty about the appropriateness of the calculated values for Kh and Kc.

Who May Find This Useful

This discussion may be useful for engineers and researchers involved in transformer design and simulation, particularly those using Ansys Maxwell or similar software for electrical modeling and testing.

GauravU
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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
 

Attachments

Is there way to address this? I think Maxwell doesn't converge if one of the windings is left unexcited
 
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
 
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Likes   Reactions: zand10000
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.
 
holy resurrected thread... o0)
 

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