In solenoid injectors, one of the reasons that the response is delayed is eddy currents, which are produced when the magnetic flux generated by current flow undergoes time variations. The eddy currents are generated in a direction that inhibits changes in the magnetic flux, causing a delay in the initial rise of the attraction force when the current begins to flow. This reduces the injector’s responsiveness. JMAG makes it possible to account for the effects from eddy currents and obtain an injector’s responsiveness by running a transient response analysis. Identifying the places where eddy currents are generated enables a designer to study whether or not responsiveness can be improved.
This Application Note explains how to apply direct current voltage to a solenoid injector and obtain its response characteristics by accounting for effects from eddy currents.
Fig. 1 demonstrates the difference in responsiveness of the plunger depending if eddy current is accounted for or not. Responsiveness is lower when eddy current is accounted for.
Attraction force characteristics
Fig. 2 shows attraction force is lower when eddy current is accounted for compared to when it isn’t accounted for. Responsiveness decreases when eddy current is raised due to a decrease in attraction force.
Fig. 3 demonstrates the valve is open at 0.003(s) when eddy current is accounted for. However, when eddy current isn’t accounted for, the valve is open at 0.0025(s). A slower responsiveness can be verified from the current flowing in the coil when eddy current is accounted for.
Furthermore, when eddy current is accounted for, there is a lot of current flowing through the coil even though attractive force is lowered, compared to when it isn’t accounted for.