A transformer (Figure 1) is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. Electromagnetic induction produces an electromotive force within a conductor which is exposed to time varying magnetic fields. Transformers are used to increase or decrease the alternating voltages in electric power applications.
Figure 1 - Power Transformer
Different types of losses are caused in a real operating transformer
Core losses, collectively called magnetizing current losses, consist of :
By Faraday's Law of induction transformer EMFs vary according to the derivative of flux with respect to time. The ideal transformer's core behaves linearly with time for any non-zero frequency. Flux in a real transformer's core behaves non-linearly in relation to magnetization current as the instantaneous flux increases beyond a finite linear range resulting in magnetic saturation associated with increasingly large magnetizing current, which eventually leads to transformer overheating.
Using EMS to simulate a transform's 3D model can help industrials to reduce these losses and thus increase the transformer’s efficiency and lifetime.
The coils used are form-wound and are of the cylindrical type. The general form of these coils may be circular or oval or rectangular. In small size core-type transformers, a simple rectangular core is used with cylindrical coils which are either circular or rectangular in form (Figure 2).
Figure 2 - 3 phases Rectangular Transformer
Application : Isolation, power transmission, grounding transformer, etc.
The example presented here is a three-phase transformer (Figure 3). The primary coils for each phase are characterized by (300 turns, 1 A/turn, 0 degrees), (300 turns, 1 A/turn, 120 degrees), and (300 turns, 1 A/turn, 240 degrees), respectively. The secondary windings are short-circuited. The windings are made of copper, and the core is composed of laminated steel with loss. In EMS, the core loss could be specified either by importing a Steinmetz (P-B) curve or selecting the coefficients of a Steinmetz loss function. In this example, the import of a Steinmetz (P-B) curve is considered.
Figure 3 - 3D Model of transform
The AC Magnetic module of EMS coupled with thermal analysis is used to compute and visualize magnetic fields and thermal results. These fields are typically caused by surges in currents or voltages. This type of analysis can be linear or non-linear. It also addresses eddy currents, power losses and magnetic forces. After creating an AC Magnetic study and thermal analysis coupling in EMS, four important steps shall be followed: 1 - apply the proper material for all solid bodies, 2- apply the necessary boundary conditions, or the so called Loads/Restraints in EMS, 3 - mesh the entire model and 4- run the solver.
In the AC Magnetic analysis of EMS, the whole properties of material are needed (Table 1).
|Components / Bodies||Material||Relative permeability||Conductivity (S/m)|
|Inner Coil / Outer coil||Copper||0.99991||57e+006|
|Outer Air / Inner Air||Air||1||0|
|Name||Number of turns||Magnitude||Phase|
|Wound Coil 1 (primary)||300||1 A||0|
|Wound Coil 2 (primary)||300||1 A||120 deg|
|Wound Coil 3 (primary)||300||1 A||240 deg|
|Wound Coil 1 (secondary)||300||0 A||0|
|Wound Coil 2 (secondary)||300||0 A||120 deg|
|Wound Coil 3 (secondary)||300||0 A||240 deg|
After running the simulation of this example we can obtain many results. AC Magnetic Module coupled with thermal analysis generates the results of : Magnetic Flux Density (Figure 6,7), Magnetic Field Intensity, Applied Current Density (Figure 8), Force density, Losses Density (Figure 9, 10) and a results table which contains the computed parameters of the model (Inductance, Current, Induced voltage, Losses etc ..) (Table 1), the electromagnetic forces . In addition to the electromagnetic results thermal results are also obtained: Temperature (Figure 11) , Temperature Gradient, Heat Flux (Figure 12).
In the results table (Table 1) we can find the induced voltage of the six coils.
EMS offers the possibility of many types of plot. Below we can observe fringe and vector plot of the magnetic flux density.