Control systems and electric controls

More and more often many devices, above all electric motors, are electronically controlled. This allows to take advantage of the optimal working points of the device and increase the overall efficiency of the system. In the last years the reliability of electronic components has grown enormously, as well as their cost has fallen.

The theory of controls is incredibly vast, but it is possible to make a general division into two macro-families: open-loop and closed-loop controls, where the second one is certainly much more effective than the first in achieving high performance, although it is more complex.

A closed-loop electronic control of an electromagnetic device can be schematically summarized as the union of:

• A comparator between the desired value of a given quantity and its real value in output from the system, measured and feedbacked
• A sensor, transducer or any other device able to measure the quantity to be controlled, eventually combined with a filter to better the quality of the output signal
• The core of the controller which generates the reference for one or more input quantities of the system, starting from the error between the desired value and the feedback
• Electronic components, which receive the command from the controller and act by modifying the topology of the circuit they are inserted in. Ideally, they behave like simple switches, but able to switch on and off very quickly. In fact, unlike the corresponding electromechanical switches, which require the movement of one of their parts, these components are able to switch simply thanks to the properties of the semiconductors of which they are properly composed. These components often belong to the so-called “power electronics”, as they see the same voltages and currents of the device itself on their terminals; they form the static converter, where the adjective “static” indicates precisely the absence of moving parts