Modeling converters in dynamic regime
Static converters for mcc speed variation

In this section, we propose to represent converters as amplifiers whose input is the control voltage $v_{\text{a}}$ and whose output is the voltage v, approximated by its mean value $\text{<}v\text{>}$ applied to the motor terminals.

The operating principle of converters is fundamentally sampled, since the control effectively acts only at ignition or blocking instants; it is also non-linear. The rigorous study of these systems quickly becomes complex and requires specialized tools, which we will present later.

To remain within the framework of classical linear servo-controls, it is traditional to admit approximations which are justified in the following cases: