Motor

Methods to Optimize Electric Motor Efficiency

Widely publicized estimates show that systems driven by electric motors consume more than half of the electricity produced in the United States and more than 70 percent of the electricity used in many industrial plants. Now that energy and operating costs are at a premium, it makes more sense than ever to increase motor efficiency.

Many facilities find it makes sense to divide their motor efficiency strategy into three phases:

• Overall assessment
• Immediate improvements
• Long-term

This article briefly outlines Step 1 and provides details on Step 2. An upcoming article will provide details for Step 3.

Phase 1: Assessment
Here’s what a motor assessment involves:

1. Survey and document how many motors, at what age, horsepower and ratings, with what level of controls are present in your facility.
2. Identify the highest and most critical loads.
3. For those key units, use a power logger to evaluate their energy consumption (power draw).

This will give you a general energy-consumption map for motors in your facility.

Phase 2: Immediate improvements
There are two kinds of immediate improvements that you can make.

1. Changes to the units and to unit operation
2. Repairs

Changes to the units may include replacing some motors with higher-efficiency or better-sized models, adding controls to others to right-size output, and rescheduling which motors run when compared to demand and utility rates.

To determine whether any of these changes make sense in your facility, use a motor efficiency calculator such as MotorMaster+ from the U.S. Department of Energy. It can help you calculate savings per motor and per efficiency step.

Otherwise, there are three inspection points that you should make to all motors that you intend to keep operational:

1. Voltage unbalance
2. Current unbalance
3. Power factor

If tests show problems with any of these three variables, correcting those problems can yield immediate efficiency improvements. Logically, you should also incorporate these tests into long-term regular maintenance to sustain any short-term improvements you make at this stage.