We all know that energy efficient motor use saves electricity and that converts to a reduction in carbon emissions. Adding adjustable speed drives is also a popular upgrade that can save even more energy on the right application.
In addition to motor and drive replacement, the mechanical power transmission components can be optimized for energy efficiency which may reduce the amount of horsepower to drive the load. On the front end, energy efficient transformers and smart starters can be added and on the load side, perhaps more efficient pumps, fans and compressors. Use of process control to ensure plant processes are in harmony will save energy and increase productivity.
But looking beyond simple component replacement will gain additional energy savings, improved reliability and productivity gains. However, more engineering redesign and benchmarking may be required to do so.
We are reaching the point where motor efficiency cannot be increased without using technology that is expensive today. The next generation of motors will be quite different from today's squirrel cage induction motors. To further reduce motor losses, the designs may change to a motor where the rotor contains permanent magnets or the motor becomes a type of synchronous reluctance design requiring a drive for its operation. Even with these super-efficient motors, it makes little sense to connect a 95% efficient motor to a 50% efficient load if the pump or fan efficiency can be improved.
When we look at the system, we should consider all components that the user can select. Sizing begins with the most efficient pump, fan or load device that is available. This will require a certain speed and torque for its operation. In some cases a motor may be directly coupled; mechanical power transmission components may be used to reduce speed and increase torque in others. Best available components should be selected which will reduce the horsepower requirements for the NEMA Premium Efficiency® motor. An adjustable speed drive should be selected when it will result in improved process control.
Premium efficient motors were first introduced in the early 1980s by motor manufacturers. In 2001 NEMA established a Premium Efficiency standard in table 12–12 in NEMA MG 1. Over the years, premium motors have been used for simple drop-in upgrades when older motors fail or when new equipment is specified. Premium Efficient motors may result in modest increases as shown by the following examples: