The first step is to survey all motors in the facility. Gather nameplate information and obtain field measurements — voltage, amperage, power factor, operating speed — under typical operating conditions. The initial focus should be on motors that exceed minimum size and operating-duration criteria.
The characteristics of motors to focus on typically include:
• three-phase NEMA design B motor
• non-specialty motors
• 10-600 hp
• at least 2,000 hours per year of operation
• constant load, not intermittent, cyclic, or fluctuating
• older or rewound standard efficiency motors
• easy access
• readable nameplate.
In conducting a motor-replacement analysis, it can be helpful to divide the motors into three categories.
The first category includes motors to replace immediately to achieve immediate payback, improved reliability or utility rebates. These include motors that run continuously — typically 8,000 hours or more a year — are inefficient or oversized, or are covered by attractive utility rebate programs. Managers should order an efficient replacement motor soon and have it installed at the next available opportunity, such as during scheduled downtime.
The second category is motors to replace at time of failure that can provide an intermediate payback. When these motors fail, managers should replace them with an energy-efficient model. Contact dealers immediately to review the efficiency and prices of available motors.
After identifying the most cost-effective replacement model, decide whether to buy it and keep it on hand as a spare or wait until the existing motor fails. This choice depends on how quickly a supplier can provide an energy-efficient motor, how quickly a failed motor needs replacing, and how many motors of the same size and type the facility uses.
The third category includes motors to leave in service because they offer extended payback. These motors already are reasonably efficient or used less than 2,000 hours each year. Managers can opt to rewind them or replace them with similar motors.
Motor Comparison: Standard vs. Energy Efficient
Energy-Efficient Motors: Are They Worth the Cost?
Surveying Motors for Energy-Efficiency Improvements
Motor Efficiency: Evaluate Power Quality, Perform Maintenance
