Pehmkäivitusmuundurid

Pehmkäivitusmuundurid, also known as soft starters, are electronic devices used to control the starting process of electric motors. They gradually increase the voltage supplied to the motor, allowing it to accelerate smoothly from zero speed to its full operating speed. This controlled acceleration reduces the mechanical stress on the motor and the driven equipment, as well as the electrical stress on the power supply.

The primary function of a pehmkäivitusmuundur is to mitigate the high inrush current that occurs when a motor is started directly across the line. This inrush current can be several times the motor's rated current and can cause voltage sags in the power system, potentially affecting other connected equipment. By employing a pehmkäivitusmuundur, the starting current is limited, which in turn reduces mechanical shock and wear on components like gears, belts, and couplings.

Pehmkäivitusmuundurid typically achieve soft starting by using thyristors or silicon-controlled rectifiers (SCRs) to control the voltage applied to the motor. The firing angle of these semiconductor devices is gradually increased during the start-up sequence, thereby increasing the voltage and motor speed. Once the motor reaches its desired speed, the pehmkäivitusmuundur may bypass itself, allowing the motor to run directly from the power supply, or it may continue to regulate the voltage for specific applications.

Beyond simple soft starting, many pehmkäivitusmuundurid offer additional features such as adjustable acceleration and deceleration times, current limiting, and overload protection. These features enhance their versatility and allow for optimization of motor control in various industrial applications, including pumps, fans, conveyors, and compressors. They provide a cost-effective solution compared to variable frequency drives (VFDs) when only starting control is required and precise speed regulation is not necessary.