Because 75% of electricity consumed in industry is used to power motors, making proper motor management decisions can reduce energy and maintenance costs as well as machine downtime.

Advanced Energy (AE) has operated an independent motor test laboratory since 1991 and has performed thousands of motor efficiency tests. During that time Advanced Energy has developed a motor management policy to benefit motor users. That policy is summarized in the following eight policy steps. Advanced Energy has developed specific tools to aid industry in the application of a cost effective motor policy.

1. Motor Inventory and Classification
If you don't know what you have, it is impossible to manage it. A motor inventory is a facility's list of the quantity, type, and location of motors. The inventory should require that each motor have a unique tracking number. Characteristics such as age, hp, rpm rating, electrical specifications, design code, frame number, enclosure type, operating hours, and application should also be recorded.

AE recommends that motors be classified based on how critical they are to the operation. We recommend critical, semi-critical, and non-critical.

• Critical - needs to be operational and running now.
• Semi-Critical - can be down one to three days without being a major problem.
• Non-Critical - can be down up to a week without being a problem.

2. Repair/Replace Decisions
The repair/replace decision for all motors should be made before they fail. Some motors will likely be cost effective to replace at the earliest opportunity, rather than waiting until failure. This is particularly true for all critical motors and those with significant energy savings potential. Advanced Energy recommends that motors be identified in some manner to notify personnel of the appropriate action at the time of failure. When a decision is made to replace upon failure, the motor tag should list all of the information needed to ensure that the appropriate motor is purchased or pulled from spares.

3. Survey and Failure Preparation for Critical and Semi-Critical Motors
Motor survey data should be used to refine the repair versus replace analysis for critical motors and to ensure that critical motors are specified properly for the driven load. Having the right motors available when critical motors fail makes it easy to take the correct actions. Evaluating the need for appropriate spares is an important and often neglected part of motor management, but is essential for planning and budgeting.

4. Motor Purchase Specification
Your purchasing department should have a written specification for motor purchase. This spec should include not only the electrical characteristics (hp, phase #, speed, etc.), but also items such as bearing type, need for grease fittings and drain plugs, etc. Of course, one of the primary parameters will be a motor efficiency specification. The electric operating cost of a motor for a single year is several times its initial purchase cost, so saving a few dollars to purchase a less efficient motor is generally a poor decision. If your purchasing department does not have written guidelines for motor purchases, it is likely that poor decisions are being made. Lacking any guidance, these poor decisions are not the fault of the purchaser.

5. Motor Repair Specification
Approximately 75% of failed motors get repaired rather than replaced. It is essential that you not only purchase high efficiency motors, but that you ensure motors are being repaired without degrading their efficiency. The bad news is that repaired motors are frequently less efficient than they were before the motor failure. The good news is that they don't have to lose efficiency when repaired. AE's before and after tests have shown that motor repairs can be done with virtually no efficiency loss if the motor is not damaged during the failure and if proper repair procedures are followed. A good motor repair policy includes using qualified motor repair vendors. Advanced Energy recommends that repair vendors be selected based on quality of repair work first, then on other attributes such as price, responsiveness, capabilities, location, etc.

6. Motor Tracking System
A motor tracking system is created by adding information and updating the motor inventory list. As motors are repaired or replaced, the motor population changes. Maintaining the inventory listing is essential for keeping the repair/replace decision accurate as well as adjusting the spares inventory. In addition, a properly used motor tracking system will identify those motors that have repeated early failures and highlight either an application, maintenance, specification or motor problem, permitting improvements that increase reliability and reduce downtime.

7. Motor Preventive/Predictive Motor Maintenance (PPM)
Advanced Energy has found that proper maintenance is necessary to ensure optimum motor life. A good PPM motor program will include a motor loading and application analysis program, a lubrication program, and a motor vibration measurement program. Other, more sophisticated techniques such as motor current signature analysis, and motor insulation characteristic testing are often used by very large companies. Motor loading contributes directly to motor life. If a motor is run in a 15% overloaded condition, it can cause as much as a 30 C rise in the motor's operating temperature causing reduction in the motor's life to as little as 1/8 of its normal operating life. Also, over lubrication not under lubrication is more likely to cause a motor failure due to excessive lubrication being deposited on the motor windings. The lubrication on the windings reduces the motor's insulating value and, ultimately premature failure.

8. Special Cases
This category is included in recognition that the seven elements of motor management previously discussed cannot account for all motor issues and situations. This component is included as a reminder to consider these special cases in refining your motor management policy. The following is a partial list of special cases that Advanced Energy has encountered in other facilities: motors other than 3-phase induction, large motors (>500 hp), special and definite-purpose motors, inverter duty motors, dc versus ac applications, metric frame motors, variable frequency drive applications, motor control issues, new motor technologies, power factor issues, motor starting issues, voltage unbalance, current unbalance, energy saving devices, power quality issues.

Improving the overall efficiency of your motor population and ensuring that you are repairing to the rated efficiencies can save you money and improve your motor reliability. For more information on motors and motor management please check out or previous newsletter articles.

Motor Reliability: Should you be paying more attention?
Motor Efficiency: Will it save you money?
Motor Ride Through - Keep your motors running
Adjustable Speed Drives