What Causes Low Electric Motor Efficiency?

What causes low electric motor efficiency?

Electric motors are central to modern industry, but many motors still operate below optimal efficiency. Today, high-efficiency motors are directly linked to energy-saving and carbon-reduction policies worldwide. In fact, for large infrastructure and municipal projects, IE3 efficiency standards are often the minimum requirement—especially when exporting motors to European countries.

Yet for motor manufacturers, improving efficiency is a complex challenge, with numerous technical bottlenecks to overcome. Measuring losses precisely, identifying key influencing factors, and quantifying each type of loss require deep expertise. Let’s break down the most common causes of increased losses in motors:

1) High Stator Copper Losses

●Large winding resistance: This can result from high-resistivity wire, small or uneven conductor diameter, or insufficient parallel strands. Connection errors or poor soldering also raise resistance, as does excessive winding turns.

●Large stator current: This can be caused by high stray losses, winding asymmetry causing unbalanced phases, severe air-gap unevenness, or incorrect winding connections.

2) High Rotor Copper Losses

●High rotor resistance: Issues include inferior aluminum or copper purity, casting defects like pores or inclusions, uneven stator slots, or use of incorrect materials (e.g., alloy aluminum instead of pure aluminum).

●Large rotor current: Errors such as using the wrong rotor core, loose lamination stacks, or excessive aluminum infiltration can increase current dramatically.

3) High Stray Load Losses

●Inappropriate winding design, slot combinations, or too small/uneven air gaps can significantly boost stray losses. Short circuits between rotor conductors and the core, or excessively long winding ends, are also common culprits.

4) High Iron Losses

●Poor-quality silicon steel or using downgraded materials (e.g., grade 800 instead of 600) reduce magnetic performance.

●Bad interlaminar insulation caused by improper processing or excessive lamination pressure leads to eddy currents.

●Insufficient core lamination count, loose stacking, and thick burrs all compromise iron weight and efficiency.

●Overheating during winding removal (e.g., burning out old coils) damages magnetic properties and insulation.

●5) High Mechanical Losses

●Low-quality bearings, misaligned bearing housings, or undersized housings causing deformation increase friction and heat.

●Incorrect fan selection or blade angle errors can add drag.

●Too much or poor-quality grease, rotor-stator rubbing (called “core rubbing”), incorrect rotor dimensions, or deformed seals also contribute to excess mechanical losses.

Reducing these losses demands rigorous quality control, precise material selection, and advanced manufacturing techniques. For manufacturers committed to global markets, meeting IE3 efficiency standards is not only a regulatory requirement but a key strategy for long-term competitiveness and sustainability.