hi everybody
can anybody tell me how to control the speed of FD Fan.as we can not control it by regulating current so wat the procedure for controling.

 

Hi, you,

The most common method of controlling the air flow-rate of a centrifugal fan is by varying the opening of some kind of damper on the output of the fan. As the damper is closed, the current of the motor will decrease, and as it is opened the current of the motor will increase.

This is "wasteful" in modern times. A (VFD) variable frequency drive is more energy efficient and easier to control. Controlling a damper will usually required an actuator with some torque. Controlling the output of a VFD usually only requires a variable 4-20 mA source.

Note that not every AC motor can be driven safely with any VFD. There are many types of VFDs, and there are many types of induction motors designed for various applications and types of VFDs.

This is a great question for a manufacturer's representative who sells industrial control equipment. By providing them the details of your fan and air flow requirements and voltage and current requirements and the nameplate data from the motor you're currently using, they can usually make at least one recommendation for controlling the air flow (which can be done by controlling the speed of the motor, or with a damper in the output).