The very principle of pulse-width simulation(PWM) has been known for a long time, but it has become relatively recently used in various schemes. It is a key point for the operation of many devices used in various fields: uninterruptible power supplies of different power, frequency converters, voltage, current or speed control systems, laboratory frequency converters, etc. He perfectly showed himself in the automotive industry and in production as an element for controlling the work of both service and powerful electric motors. The PWM controller has proven itself well when working in different circuits.
Let's look at some practicalexamples showing how you can adjust the speed of rotation of the motor using electronic circuits, which include a PWM controller. Suppose that you need to change the speed of the electric motor in the heating system of the interior of your car. Enough rewarding improvement, isn't it? Especially in the offseason, when you want to regulate the temperature in the cabin smoothly. The DC motor installed in this system allows you to change the speed, but you must affect its EMF. With the help of modern electronic elements this task is easy to accomplish. For this purpose, a powerful field effect transistor is turned on in the motor supply circuit. Manages it, you guessed it, PWM speed controller. With it, you can change the speed of the motor over a wide range.
How does the PWM controller in the circuitsalternating current? In this case, a somewhat different regulation scheme is used, but the principle of operation remains the same. As an example, consider the operation of the frequency converter. Such devices are widely used in manufacturing to control the speed of engines. To begin with, the three-phase voltage is rectified with the help of the Larionov Bridge and partially smoothed out. And only after that it is fed to a powerful bipolar assembly or a module based on field-effect transistors. It controls the same PWM voltage regulator, assembled on the basis of the microcontroller. It forms the control pulses, their width and frequency, necessary for the formation of a certain speed of the electric motor.
Unfortunately, in addition to good operationalcharacteristics, in circuits where a PWM controller is used, there is usually strong interference in the power circuit. This is due to the presence of inductance in the windings of the electric motors and the line itself. They are struggling with this most diverse circuit design: they install powerful surge protectors in AC circuits or they set up a reverse diode in parallel with the motor in DC power supplies.
Such schemes are quite highreliability in operation and are innovative in the field of control of electric drives of various capacities. They are quite compact and well managed. The latest modifications of such devices are widely used in production.
