Figure 3. Up Escalator kW
The efficiency curve for typical AC motors is shown in Figure 1. As a rule of thumb, the larger the motor, the flatter this curve is, and the lower the load percentage has to drop before the efficiency starts to drop. The technology in Power Efficiency’s ESS+ attacks the energy wasted when motors are lightly loaded — to the left of the dotted line in Figure 1. There is no opportunity for savings with the ESS+ technology when the motor is heavily loaded and operating efficiently.

To save energy, the ESS+ constantly monitors the voltage and current going to the motor. When the voltage and current sine waves diverge greatly — when the phase lag increases — the motor is lightly loaded and operating inefficiently. When this happens, the ESS+ technology reduces the current and voltage appropriately, while always maintaining the motor at a constant (full) operating speed. When the load on the motor increases, the ESS+ reads this condition and increases the power to the motor so it does not stall.

Although the theory of making motors more efficient in this manner was introduced many years ago, the process has been very difficult to perfect. The maximum amount of savings is realized across multiple applications and the motor receives full power when the load on it increases. Power Efficiency has created new technologies, including algorithms and software, to optimize the operation of the ESS+.


Power Efficiency’s energy saving soft start technology has been proven to save 25 – 50% of the energy consumed by an electric motor, depending on the load and operation of the machine. In a recent test by Nevada Power Company (the electric utility for southern Nevada) on an escalator motor at a major casino on the Las Vegas Strip, the device reduced the average power consumption by 34%.

Figures 2 and 3 represent the kilowatt usage of the escalator over a period of 10 days, displaying 5 days with the energy savings technology activated and 5 days without it. Other potential applications for Power Efficiency’s soft start technology include rock crushers, compressors, conveyors, pumps, saws, mixers, shredders, and injection molding machines. With energy prices on the rise and increasing concerns about green house gas emissions, Power Efficiency introduces a smart option for energy savings on electric motors. Power Efficiency’s patented energy saving technology and intelligent product features represent significant advancements in soft start capabilities for electric motor efficiency and the environment.

This article was written by John Hurst, Director of Engineering at Power Efficiency Corporation. For more information, contact Mr. Hurst at This email address is being protected from spambots. You need JavaScript enabled to view it. or visit

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