What system is commonly used for variable frequency drives?

The commonly used system for variable frequency drives (VFDs) is analog control. This is because VFDs primarily operate by varying the frequency and voltage supplied to an electric motor in order to control its speed and torque. Analog control provides a smooth and continuous adjustment of the power supplied to the motor, which is essential for applications requiring precise speed regulation.

In many cases, VFDs can accept analog signals to determine the desired output frequency. These analog inputs, such as 4-20 mA or voltage signals, allow for real-time adjustments based on feedback from the system, making the control method optimal for managing motor operations in a dynamic environment.

While discrete control involves on/off operations and may not be suitable for the varying speeds needed in most VFD applications, continuous control focuses more on maintaining a steady-state output rather than making variable adjustments. Hybrid control is a mix of various control strategies, but for the specific purpose of operating variable frequency drives, analog control remains the more effective and commonly utilized choice. This capability of providing fine-tuned, variable control is vital for ensuring efficient motor operation across different loads.