Control system for a single phase motor, for instance a motor in a ventilator system

摘要

A device for controlling the rotational speed of a single phase alternating current motor and as an example a motor (5) in a ventilator system and where this regulation is done since in a phase conductor 1 there is a transistor switch 3 and a motor 5 and where the transistor switch (3) has a capacitor (4) connected in parallel and where inside the motor (5) there is a second capacitor (6) connected. The principle for the control of the rotational speed is done with a pulse width modulation of the alternating current and this pulse width modulation is obtained since the transistor switch closes at the zero-crossing and remains closed to a optional point at the sine wave when the transistor switch opens when the capacitor (4) is charged instantaneous to after that start the discharge of the same, which means that the voltage over the motor (5) do not fall to zero, instead a gradual reduction of the voltage occurs, which results in a that the motor is running more smoothly and silent.