With rising energy costs and growing concerns about climate change, any energy-efficient solution in industrial plants and commercial building installations is welcome. Minimizing energy costs is an ongoing concern for business managers. Electric motors and drive systems account for more than 60% of UK industrial electricity demand. A large number of these motor units drive fans, pump conveyors and compressors. So are variable speed drives energy efficient ?
To understand how variable speed drives save energy, you must first understand variable speed drives. Variable speed drives vary the speed of an AC or DC motor. They increase efficiency and provide greater control over fixed speed motors. Variable frequency drives are similar, but they operate a little differently than variable speed drives. Variable speed drives control the motor by varying the input voltage. Variable frequency drives are controlled by varying the input voltage and frequency.
Variable speed drives are not suitable for all applications. However, they can save significant energy and reduce costs in a wide range of industrial plant and commercial building operations. How are variable speed drives energy savings?
Motor Speed Adjustment: The cube-law relationship between speed and power is one of the main drivers of variable speed drives. Fans and pumps rarely need to run at full speed. As a result, variable speed drives can adjust motor speed to meet application needs and save power.
Motor Size: In some applications, engineers match motor size to peak duty cycle demands. This peak may only occur at startup or for a short period of time. For continued energy savings, smaller motors can be combined with variable speed drives. In this case, the motor is sized for normal application requirements, and the variable speed drive increases the output to cover short-term peaks in the duty cycle.
Motor Replacement: Variable speed drives save energy now that older, less energy efficient motors can be replaced with newer models that incorporate variable speed drives.
Sensors and Feedback Loops: Variable speed drives have a certain level of intelligence and are programmable. When combined with sensors and feedback loops, they can control multiple motors. This saves energy throughout the installation.
Constant-torque motors: Variable- torque motors, such as fans and pumps are parts of variable speed drives energy savings. That said, it's important not to overlook constant torque motors. Using variable speed drives to control soft-started conveyors saves energy. Variable speed drives can also help ensure conveyors operate at peak efficiency. There are many constant torque motor applications where variable speed drives can pay for themselves in the medium to long term.
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