modelVaryingResistance

Information

This example shows a purely electric circuit containing a VariableResistor component (R3). The resistance of R3 is determined depending on time function of component Ramp. It starts at a very small value (0.01 Ohm) and reaches 5 Ohm after 10 s.

Using this example, we would like to give an idea how one can decide if the system is in a quasi-stationary mode or not.

The main (and only) time constant of the system reads T = L*(R2+R3)/(R2*R3). It is well-known for first-order components that, after a step-like change of an input signal, the output signal reaches 95 % of �ts final value after a time period of 3*T. This time period is called decayTime. Checking the difference between decayTime and the time interval of the simulation experiment yields the information if the system is in a quasi-stationary mode.

Because of variable resistor R3, it is necessary to calculate decayTime during the simulation experiment according to decayTime = 3*L*(R2+R3)/(R2*R3). The Boolean quasiStationaryOk tests if decayTime is smaller than the simulation interval tInterval (which is necessary for quasi-stationary mode). Hence in the first part of the simulation (Time < 2.4 s), the system is not in a quasi-stationary mode and the appropriate points in time of the result curves represent only a series of steady states without any correlation with time. In the second part of the simulation (Time > 2.4 s), the system is quasi-stationary and the result curves reflect a correct relationship with time.

Simulate until 10 s.

• V.v,  R2.v,  and  L.v  versus "Time"
• L.vRe  and  L.vIm  versus "Time"
• quasiStationaryOk versus "Time"

Parameters

Components