The largest benefit in energy efficiency improvement comes from a systematic integration and‐optimisation of all mechanical and electrical components in a total motor system.Four major areas are involved (Table 29).

The major element for improving electric motor system efficiency is better engineering practices‐in the following areas: Life cycle cost: consider avoiding minimal first cost, decisions on repair versus replacement.‐Integrated machine design: OEMs tend to focus on production at low initial cost rather thanefficiency. Packaged products: component integration to avoid the addition of maximized separateelements. Adequate sizing: calculated safety factors to avoid general over-sizing practice. Efficient operation: factory automation systems with precise on/off and partial load controls‐to avoid hours of operation without any use.

As illustrated in Figure 34, motor system efficiency can be improved from 42% to 63% or the total ‐required grid peak load can be reduced from 240% to 160% of the net mechanical load. The improvement (red surface) results from several individual and consecutive improvement steps.

The efficiency of an electric motor driven system (EMDS) (such as a pump, fan, compressor or‐industrial handling and processing) is determined by the total motor system, i.e. themultiplication of efficiencies for each component. Within the various electric motor technologiesdescribed, energy savings options are available for both components and integrated systems.‐

Designing the total motor system (the entire application from supply grid to output product) is acomplex task. To achieve cost effective installations and machines that operate safely and‐reliably, the engineering approach must set high targets for energy efficiency and apply anintegrated design model. It is important to question production demands (capacity, speed, andenvironment) before selecting technical components.

Gears and transmissionsMotor systems experience losses in other mechanical components. Gears and transmissions aretwo mechanical elements which offer significant potential for improved efficiency. In motorefficiency of around 100 kW output, just two percentage points separate one motor efficiencyclass from the next. This means it can be easier or more cost effective to change transmissions‐and gears to achieve the same overall performance improvement.

Gears are used in some applications to convert motor speed to the required speed. Some typesof gears (worm gears with very high gear ratios) can be very inefficient: the larger the gear ratio(relationship of the two revolutions per minute [rpm]) and the more gear stages used, the lowerthe efficiency. Gear losses come from tooth friction and lubrication churning. Losses tend to bebetween 2% and 12% higher in new gears until the teeth are smoothed.

Variable loads and VFDs

The control technology used for adjusting motor, voltage and frequency to deliver only and precisely

the required torque and speed is an electronic controller known as a “variable frequency drive”‐(VFD) (Figure 19). This independent component lies between the grid and the motor and consists ofan AC/DC converter, a DC link and filter, and a DC/AC inverter. The VFD is mostly based on pulsewidth modulation. It has power demand in both standby and subsequent variable operationalmodes, so additional losses of a VFD have to be over compensated by reducing losses in partial load.‐Many of the new motor technologies operate with variable speeds.

Many motor applications have high operating hours but variable loads. Even with the relativelyflat efficiency curve of larger IE3 motors (between 50% and 125% load), there are still large gainsto be made by adapting motor speed and torque to the required load. The largest benefit comeswith pumps and fans in closed loops for which power consumption varies as a cubic power oftheir rotational speed.