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Single-phase transformer
Applications
Single-phase transformer
In this application note, EMS is used to study a single-phase transformer. AC Magnetic module of EMS coupled to thermal solver both are utilized to compute and generate magnetic fields, electromagnetic losses including coreloss, excess loss, hysteresis loss, eddy loss, and temperature evolution of the studied transformer.
SOLIDWORKS model of a Single-phase transformer
The SOLIDWORKS model of a single-phase transformer consists of a core, an inner coil and an outer coil, as shown in Figure 1. The transformer core is made of M27.
Coupling to Thermal Analysis
Thermal analysis calculates the temperature distribution in a body due to conduction in the solids. A convection boundary condition is allowed to define what happens to the heat flux in the extremities of the model.
In EMS, Thermal analysis automatically follows an electromagnetic analysis so that the heat sources in the model are automatically pre-computed.
Material
The simulated model is composed of a laminated steel core, an inner coil, an outer coil and Air. The materials properties are summarized in Table 1. The coreloss PB curve of the core material is shown in Figure 2.
| Component | Material | Relative permeability | Electrical Conductivity (S/m) | Thermal Conductivity (W*m-1 * k-1) |
| Core | laminated steel (M27 at 0.36mm; Mass density: 7650 kg/m^3) | Nonlinear | 2.32558 e+006 | 43 |
| Inner Coil/ Outer Coil | Copper | 0.99991 | 5.7e+007 | 401 |
| Coils Air, Inner Air, Outer Air | Air | 1 | 0 | 0.024 |
Primary/ secondary windings - Open circuit case
In this simulation, the inner and outer coils are modeled as wound coils. Primary winding is current driven coil with an input current of 10*300 A-turns.The secondary side of the transformer is made of 600 turns open-circuit winding. The operating frequency is 60Hz.
Thermal Inputs
Convection is the heat transfer mode in which heat transfers between a solid face and an adjacent moving fluid (or gas). In EMS, all air bodies (Outer Air, Inner Air and Coils Air) are applied a convection boundary condition.
Convection coefficient was set to be 10 W/ (m2 *k), and the Bulk ambient temperature was set to be 300 Kelvin.
Mesh
To achieve a good accuracy without increasing the total number of mesh elements, it is recommended to apply a mesh control to the regions where a large variation is expected. Figure 3 shows the resulting mesh.
Simulation and results - Open circuit condition
EMS enables to compute and generate several output data, including magnetic fields, EM losses, currents, voltages, inductance and resistance matrices, etc, which allow to design and optimize different types of transformers. Figure 4 shows the magnetic flux density of the transformer core. The maximum magnetic fields are located along the middle leg of the transformer. It reaches 2.1T. The fluxes in both sides legs are ranging from 1T to 1.7T. Cross section view of the magnetic field vector plot is demonstrated in Figure 5.
Figure 7 - Temperature results of the transformer
Figure 7 - Cross section view of the temperature results
Conclusion
Using EMS, the AC Magnetic study coupled to thermal analysis helped to study and compute different results related to a single phase transformer. Magnetic fields, EM losses, winding parameters, temperature are calculated and generated under open-circuit condition. Moreover, EMS allows to simulate transformers under different conditions such as short circuit, with loads (resistive, capacitive and inductive loads) and multiple connections types, etc.
