High-efficiency motors are closely tied to global energy conservation and emission reduction policies. IE3 energy efficiency has become the basic threshold for motors in national key projects, municipal tenders and especially exports to European countries. However, motor manufacturers face great challenges in efficiency improvement, with key technical bottlenecks including loss measurement, identification of efficiency-influencing factors, and quantitative analysis of loss causes. This article briefly analyzes the core causes of excessive motor losses that lead to low efficiency.
Excessive Stator Copper Loss
- High winding resistance: Caused by high wire resistivity, small/uneven wire diameter, insufficient parallel windings, incorrect wiring, poor welding, or more winding turns than designed.
- High stator current: Stemming from other excessive losses, three-phase imbalance due to winding asymmetry, severe air gap unevenness, fewer winding turns than normal, or wrong wiring connections.
Excessive Rotor Copper Loss
- High winding/conductor bar resistance: Resulting from high aluminum/copper resistivity, casting defects (air holes, impurities, thin bars) in cast aluminum rotors, irregular stator slots, loose aluminum structure from improper casting parameters, non-compliant materials, or incorrect rotor matching.
- High rotor current: Caused by wrong rotor, improper aluminum material for casting, or poor rotor core lamination leading to excessive transverse current.
Excessive Stray Loss
Main causes: Improper selection of stator winding type/pitch and stator-rotor slot matching, overly small/severely uneven air gap, severe short circuit between rotor conductor bars and core, and overlong stator winding ends.
Excessive Iron Loss
Key factors: Inferior or misused silicon steel sheets; poor stator core interlaminar insulation (untreated, damaged by excessive lamination pressure, or short-circuited from machining); insufficient core laminations and inadequate weight (missing sheets, poor compaction, large punching burrs, over-thick paint); severe magnetic circuit saturation; high no-load stray loss (included in iron loss during testing); and core overheating (from open fire/electric heating when removing windings) leading to reduced magnetic conductivity and insulation damage.
Excessive Mechanical Loss
Common causes: Poor bearing quality/assembly; incorrect fan matching or wrong blade angle; misaligned bearing bores of frame and end covers; undersized bearing bore causing outer ring deformation; excessive or low-quality grease in bearing bores; stator-rotor rubbing; incorrect rotor axial dimension leading to jamming; misaligned/deformed oil seals/water slingers; and fan rubbing with associated components for fan-equipped motors.
Post time: Mar-07-2026