Pehmkäivitusmuundur

Pehmkäivitusmuundur is a Finnish term that translates to "soft starter converter" or "soft starter." It is an electronic device used in industrial applications to control the starting of AC electric motors. Instead of directly connecting the motor to the full power supply, which can cause a large inrush current and mechanical stress, a soft starter gradually increases the voltage supplied to the motor over a short period. This controlled ramp-up of voltage results in a smoother acceleration of the motor, reducing mechanical shock to the driven equipment and the electrical stress on the power system.

The primary function of a pehmkäivitusmuundur is to limit the starting current. When an AC motor starts, it can draw several times its normal running current. This high current can cause voltage dips in the power supply, affecting other connected equipment, and can also lead to premature wear on motor components and driven machinery like belts, gears, and couplings. By controlling the voltage, the pehmkäivitusmuundur also controls the starting torque, preventing sudden jerks.

Pehmkäivitusmuundur typically use solid-state components, such as thyristors or silicon-controlled rectifiers (SCRs), to regulate the voltage. These components can be triggered at specific points in the AC waveform, effectively controlling the amount of voltage that reaches the motor. Once the motor reaches its desired speed, the soft starter can bypass itself, allowing the motor to run directly from the full line voltage, or it can continue to regulate the voltage if needed for specific applications. They are commonly found in pumps, fans, conveyors, and other industrial machinery where controlled starting is beneficial.