In the “ElectroMagnetics” tab, users assign terminals (positive, negative, or disconnected) and designate the windings as either primary or secondary sources. Additionally, connections between turns within each coil group and across coil groups within the same winding are defined. Further winding connections and orientation adjustments can be made in the Circuits tab.
The workflow to set up the electromagnetic connections is as follows:
- Enable Secondary Winding and 2nd Secondary Winding if needed
- Specify the Excitation type of sources connected to the windings, such as current, voltage, or circuit (only for secondaries).
- Set the Connection type between coil groups within each winding
- Add Additional Coils (e.g., when connecting the inductor to the transformer) if needed
- Select the Winding type (primary, secondary, 2nd secondary, additional coil) from the Coil Group table
- Set the Connection type between individual turns within a Coil Group
- Switch to Terminals selection and make any necessary changes to winding terminals.
Winding and excitation configuration for electromagnetic simulation of hybrid transformer and inductor
Excitation – Connects windings to voltage, current, or circuit sources. We recommend using current sources whenever possible, as they uniquely define the magnetizing current and magnetic field. For further details, refer to our article discussing the importance of current in calculating core losses during transient simulations.
IMPORTANT: You cannot simultaneously set both current and voltage as excitation sources, and power cannot be directly used either.
Coil group connection type – Defines the connection between coil groups within the same winding:
- Series: Results in identical current among all coils.
- Parallel: Results in equal voltage among all coils, with the current being split.
2nd Secondary Winding – This winding can be useful for center-tapped windings, auxiliary windings, or when the secondary winding is composed of split coils that require connection via circuits.
Additional Coil – Any additional coils can be connected to existing windings. For example, a transformer and an inductor can be solved within the same simulation by connecting the additional coil to the transformer windings.
Connection – Defines the connection on a lower level – inside coil groups on a turn level.
- Series: Default setting results in identical current across all geometries. Resistance and voltage are calculated as a sum.
- Parallel: Results in equal voltage across all geometries within the coil group. It is occasionally used to connect separate solid or litz wire turns.
Terminals
In the terminal preview, you can designate terminals as Positive, Negative, or Undefined (disconnected terminal, no current flow). Ensure that each turn geometry has at least one positive and one negative terminal to define the current direction.
IMPORTANT: A common mistake in transformer setups is failing to consider the current direction in primary and secondary windings. In simplified transformer models, the currents in the primary and secondary windings flow in opposite directions. The net ampere-turns (product of turns and current) from both windings form the magnetizing current and magnetic field, determining the losses. When the ampere-turns in the primary and secondary windings are equal but flow in opposite directions, the magnetic flux in the core cancels out, leading to zero hysteresis losses.
Terminal setup for electromagnetic simulation of hybrid transformer and inductor
You can also set multiple positive or negative terminals. In this case, the solver will apply the same voltage to all terminals of the same type while splitting the current among them.
TRAFOLO requires windings/conductors to have at least one positive and one negative terminal.
