The very principle of pulse-width simulation (PWM) has been known for a long time, but it has been used in various circuits relatively recently. It is a key moment for the operation of many devices used in various fields: uninterruptible power supplies of various capacities, frequency converters, voltage, current or speed control systems, laboratory frequency converters, etc. It proved to be excellent in the automotive industry and in production as an element for controlling the operation of both service and powerful electric motors. The PWM controller has proven itself well in various circuits.
Let's look at some practical examples showing how you can control the speed of an electric motor using electronic circuits that include a PWM controller. Suppose you need to change the speed of the electric motor in the heating system of your car. Quite a useful improvement, isn't it? Especially in the off-season, when you want to regulate the temperature in the cabin smoothly. DC motor installed inthis system, allows you to change the speed, but you need to influence its EMF. With the help of modern electronic elements, this task is easy to accomplish. To do this, a powerful field-effect transistor is included in the motor power circuit. Manages it, you guessed it, PWM speed controller. With it, you can change the speed of the electric motor over a wide range.
How does a PWM controller work in AC circuits? In this case, a slightly different control scheme is used, but the principle of operation remains the same. As an example, consider the operation of a frequency converter. Such devices are widely used in production to control the speed of motors. To begin with, the three-phase voltage is rectified using 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 is controlled by a PWM voltage regulator assembled on the basis of a microcontroller. It generates the control pulses, their width and frequency, necessary for the formation of a certain speed of the electric motor.
Unfortunately, in addition to good performance, in circuits where a PWM controller is used, strong noise in the power circuit usually appears. This is due to the presence of inductance in the windings of electric motors and the line itself. They are struggling with this with a wide variety of circuit solutions: they install powerful surge protectors in AC circuits or put a reverse diode in parallel with the motor inDC power supply circuits.
Such circuits are distinguished by a sufficiently high reliability in operation and are innovative in the field of controlling electric drives of various capacities. They are quite compact and well managed. The latest modifications of such devices are widely used in production.
