Asynchronous motors are the most commonly used electric motors. Their biggest disadvantage is that we can not change their rotational speed easily. If using a frequency converter, the problem of rotational speed control is simply solved. The thesis presents some of the capabilities of a modern frequency converter. Since these frequency converters have many functions today, they are best controlled through computer software. In our case, the CX-drive software package was used to control the electric motor. Our frequency converter also makes it possible to use PID controller integrated in the frequency converter.