How do PAYBACK variable speed drives save energy if the motor runs continuously?
Because of the nature of the descending torque load itself, the magnetic-coupled drive takes advantage of the energy savings with variable speed. [Graph] The magnetic-coupled drive will take advantage of the affinity laws on variable torque loads such as centrifugal fans and pumps and does so without altering the voltage or interrupting power to the motor. Even with the motor running continuously, the kW required by the motor changes according to the actual load, i.e.: -loading and unloading of the motor by varying the speed of the load via magnetic coupling between the motor and the load. What you always pay for is the amount of kW used and even with the motor running continuously, the difference in the amount of kW required of any 3 phase motor from no load to full load is very significant. As example: 7-1/2 hp motor/3phase/60hz (Typical Blower Application) Measured @ Full Load, max fan speed (typical) = 5.60 kW Measured @ Min Load, min fan speed = approximately 0.40 to 0.50 kW GREAT
