What we have done, and what we are doing
to help reduce energy consumption

Part 5: REWINDING MOTORS FOR
IMPROVED EFFICIENCY

| The Effects of Losses of Motor Rewinding | Rewinding with Integrated Capacitors |

As motor efficiency becomes an important concern for motor users because of the high cost of electric energy, motor users frequently face the question today, "Should I buy a new motor or rewind an old one?" This question does not have one single, best answer which is right for all situations. However, as energy costs continue to rise, the decision is more frequently going to be to buy a new motor.

As discussed previously, motors are inefficient because of watts lost in the five areas of a motor. In order to improve efficiency, these losses must be reduced or minimized. In new product lines of energy efficient motors, such as the Reliance XE line, the greatest efficiency improvements resulted as each of the losses were minimized by a combination of improved materials, engineering design and improved manufacturing processes (Figure 14).

The Effects of Losses of Motor Rewinding

During a motor failure or in the stripping of the winding from the stator core prior to rewinding, high temperatures can occur. These temperatures can, in many cases, effect the electrical characteristics of the stator core steel and result in increased iron losses and lower motor efficiency.

Overall, manufacturer specifications must be met or the original motor performance will be degraded. Specifically, care must be exercised in the motor winding stripping process so that motor manufacturer’s temperature limits are not exceeded or increased core losses will result.

The only area of possible loss reduction available during the rewinding process is the ohmic (l² r) losses in the stator. This is done by rewinding the motor with a larger diameter wire so that the effective conductor area is increased, resulting in a lower winding resistance. The effect is to lower the stator l² r loss, but it does not affect the other losses.

Rewinding for lower stator resistance is possible only if additional slot space is available by the original stator slot not being full of copper or by utilizing new, thinner insulating material replacing old materials thereby making more space. It follows that not all motors are candidates for efficiency improvement by rewinding.

In contrast to a rewound motor, energy efficient motors, such as the Duty Master XE motor, reduce all five components of losses as well as provide additional mechanical features which provide long, dependable motor life.

Rewinding With Integrated Capacitators

Special rewind methods do exist incorporating special windings with capacitors in the circuit and claim to not only improve efficiency and power factor, but improve performance on non-ideal power lines such as low or unbalanced voltage. Reliance has analyzed and tested these methods and found many of these claims to be false.