Cascade speed regulation of three-phase asynchronous motors

Cascade speed regulation refers to the use of an adjustable additional potential in the rotor circuit of a wound motor to change the motor's slip and achieve speed regulation. Most of the slip power is absorbed by the additional potential introduced in series, and then used to generate additional devices to return the absorbed slip power to the grid or convert it into energy for utilization. According to the absorption and utilization method of slip power, cascade speed regulation can be divided into motor cascade speed regulation, mechanical cascade speed regulation, and thyristor cascade speed regulation. Thyristor cascade speed regulation is often used, and its characteristics are:
1. The slip loss during the speed regulation process can be fed back to the power grid or production machinery, with high efficiency;
2. The device capacity is proportional to the speed regulation range, which saves investment and is suitable for production machinery with a speed regulation range of 70% -90% of the rated speed;
3. When the speed control device fails, it can be switched to full speed operation to avoid shutdown;
4. The power factor of thyristor cascade speed regulation is low, and harmonic effects are significant.
This method is suitable for use on fans, water pumps, steel mills, mine hoists, and extruders.