Educational And Training Videos
VFD Control Modes Explained: V/Hz, Vector, and Flux Control - from AutomationDirect
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Typical modern drives have 2 velocity control modes: volts/hertz and vector, or flux control. Volts hertz or volts frequency simply uses an internal curve like this to send a specific voltage and frequency to the drive based on the speed command. When constant torque is needed, vector or flux mode is more appropriate. On many drives, vector control is sensorless. In this mode, the drive controls the motor speed based mathematical models, with the advanced processors used in VFDs today, this provides very good speed control, acceptable for most applications. However, sensorless vector and volts hertz modes are not well suited for accurate speed control and torque at lower speeds, which brings us to the closed-loop control. VFDs with full closed-loop vector or flux control add one additional input into the mathematical model: the physical position of the motor shaft measured by an encoder. This allows the model to precisely adjust to any errors between the commanded speed or torque and the actual speed or torque. This model provides full torque and excellent speed control, especially at low speeds. Please click the link below for more details in the long-form video.
