Starting Method for Centrifugal Blowers

VFD's provide significant energy savings. The variable torque variety is recommended for fans and pumps. Ramp up and down on start and stop to avoid the effect of inrush and belt wear. If you intend to vary the speeds continually or run at less than rated voltage and frequency for lengthy periods consider using inverter duty motors.

VFDs only save energy in loads like centrifugal pumps and fans IF THE SPEED IS TURNED DOWN, and only in comparison to other methods of varying the flow. If there is no need to vary the flow rate, a VFD will actually WASTE energy.

Soft starters do not save energy on pumps and fans.

So if you want to consider the benefits of soft starting on the wear and tear of mechanical components and the motor itself, that is a good reason to consider them and in my experience a good enough reason to use them.

VFDs inherently soft start as well, but see above. The only time to consider a VFD as a "glorified soft starter" is when your starting current restrictions are so severe that a soft starter will not limit the current low enough.

Dear Guest, If you kindly come out of the closet and reveal your e-mail id I could mail across a fair comparison of various starting methods. Generally in Asia., the other problems faced with soft starters and VFDs is deterioration of Power Quality - specifically Harmonics. Mainly because filters / chokes may or may not necessarily be installed along with these ''electronic'' devices. I would say that ATS with Korndorfer Closed Transition would be the best bet in such applications. Advantages - High Torque, Soft Starting, Reduced Inrush Current, Zero Maintenance, Marginal Energy Saving etc. Disadvantages - Bit Bulky. Cheers, RRV

A variable speed drive may allow you to operate at a lower speed than calculated which will save on your electrical consumption. Soft start is not critical on most centrifugal fan applications