Power control in simulations

Power control is the most widely used induction heating process control available. Power supply manufacturers offer different types of control such as current, voltage or even frequency control, but the power control remains the most popular one.

Process engineers who are overseeing the heating very often do not even know the actual current or voltage values in the inductor, as it is not relevant to the process supervision. When a simulation is built to optimize the heating process, many engineers stumble upon the fact that they cannot use power as an input - instead they need to define the current or voltage in the inductor. Why?

Physics behind an induction heating simulation

The electromagnetic side of the induction heating in its base is governed by the well-known Maxwell equations, which together define the relations between the electrical charges, currents, and electric and magnetic fields. These equations and their derivations are used not only in

CENOS, but in every simulation software which can calculate electromagnetics.

The problem is that the power value which is known to the process engineers cannot be used as an input in these equations, making it fundamentally impossible to carry out power controlled induction heating simulations.

We now understand the reason why we can't use the power as an input in a simulation, but that does not resolve the problem of what to do when only the power value is known. In such a situation multiple approaches can be used depending on the simulation setup.

Without B(H) (constant permeability)

In everyday calculations and initial design iterations, the B(H) curve will probably not be used in material definitions to save the calculation time. If you do not use a B(H) curve in your simulation, you can easily calculate the current value which corresponds to your desired power value with just one simulation.

1. Choose one random current value and run 1 time step of purely electromagnetic simulation as it will take much less time to calculate (you can easily disable thermal analysis in the Induction Heating physics). You will find the power value corresponding to the current you defined.

2. Without the B(H) curve the power value is proportional to the current. We can calculate the necessary current value if we know the relation between I1 and P1.

Once you have calculated the necessary current I2 to get the desired power P2, you can enable thermal analysis, enter the calculated current value, and run the simulation with a specified power.

With B(H)