DN0005, 3-Phase Induction Motor Drive Using a V/F Control Design Note

For loads where the load curve is well known, such as a fan, a simple V/F drive can provide good efficiency and reasonable speed control without the need for any speed feedback. In such an application, the actual rotation speed is the commanded speed less the slip. This is the same operating mode as if a motor were connected directly to the mains, but we have the added advantage of being able to control the drive frequency and therefore we have a low cost and easily implemented speed control. The original application of this board was a small fan used in a residential heating system