High-efficiency motors are directly related to energy conservation and emission reduction policies, and many national key projects and municipal projects must meet the IE3 energy efficiency assessment requirements, especially motors imported into European countries through export, which are almost the minimum thresholds.

However, for motor manufacturers, it is too difficult to improve efficiency, and there are many bottleneck technologies to be broken through, such as the measurement of loss, the determination of key factors affecting motor efficiency, the causes of loss and quantitative analysis, etc. First, start with the causes of increased loss, and decompose and analyze them one by one.

The stator copper is greatly damaged

● Large stator winding resistance: (1) The resistivity of the wire is large or the wire diameter is small, the wire diameter is uneven or the number of winding roots is small; (2) Wrong wiring or poor welding; (3) The actual number of turns is more than the design value.

● Large stator current: (1) Other losses are large; (2) The three-phase is unbalanced due to the asymmetry of the stator winding; (3) The stator rotor air gap is seriously uneven; (4) Because the number of turns is less than the normal value, the resistance will be less than the normal value; (5) The winding wiring is incorrect.

The copper of the rotor is greatly damaged

● Large resistance of rotor winding (or guide strip): (1) The resistivity of aluminum (copper) is large; (2) There are air pores or impurities in the cast aluminum rotor guide bar or end ring, or there is a local thin strip problem caused by casting defects; (3) The stator groove is not neat (manifested as groove sawtooth), and there are misaligned pieces and reverse pieces, resulting in insufficient effective area of the rotor groove; (4) Due to the improper selection of cast aluminum parameters, the structure of aluminum is loose, which directly leads to the increase of resistivity. (5) The material does not meet the requirements, such as the use of alloy aluminum for ordinary aluminum rotor; (6) Using the wrong rotor, etc.

● High rotor current; (1) Use the wrong rotor; (2) Wrong aluminum is used when casting aluminum, such as ordinary aluminum is used in alloy aluminum rotors; (3) The rotor core is not stacked, resulting in a large area of inter-piece aluminum feeding, resulting in excessive transverse current of the rotor.

The stray loss is large

● Improper selection of stator winding type or pitch;

● Improper selection of stator and rotor grooves;

● The air gap is too small or severely uneven;

● Severe short circuit between the rotor guide and the iron core;

● The end of the stator winding is too long, etc.

The iron damage is great

● Poor quality of silicon steel sheet or wrong use of materials, such as 600 material is mistakenly used for 800 grade downgrading; For motor factories that purchase iron cores, special attention should be paid to this issue.

● Poor insulation between stator core pieces: (1) No insulation treatment or poor treatment effect; (2) The pressure is too high when the iron core is stacked, which damages the insulation between the pieces; (3) When the inner chamber of the car stator or repairing the core of the file, it leads to a short circuit between the core piece and the piece (this problem exists in most iron core manufacturers).

● Insufficient number of iron core pieces and insufficient iron weight: (1) Insufficient number of pieces (missing pieces); (2) The stacking pressure is small and not compacted, and the direct result is insufficient iron weight; (3) The burr of the punch is large, and the iron weight cannot be guaranteed when the iron length is in line; (4) The paint is too thick, which is a direct quality problem of silicon steel sheets.

● The magnetic circuit is too saturated, and the relationship curve between no-load current and voltage is bent severely.

● The no-load stray loss is large, because it is included in the iron loss during the test, so the iron loss appears large.

● When the winding is dismantled by fire or electric heating, the core will overheat, resulting in a decrease in magnetic conductivity and damage to the insulation between the pieces. This problem mainly occurs when the winding is taken out by fire after the winding fails; Some motor manufacturers have sought a way to remove the windings by lye immersion.

Large mechanical losses

● The bearing or bearing assembly quality is not good, at this time the bearing will heat up seriously or rotate inflexibly.

● The external fan is used incorrectly (such as the 2-pole motor uses a 4-pole fan) or the fan blade angle is wrong; According to the conventional design, the 2P motor fan is relatively small, and the method of reducing losses by adjusting the fan method is very effective, but the premise is to ensure the temperature rise performance of the motor.

● Different axes of the machine base and both end cover bearing chambers;

● The diameter of the bearing chamber is small, which makes the outer ring of the bearing under pressure and deformation, resulting in increased bearing friction loss; This can also lead to bearing overheating failure.

● Too much grease or poor grease quality in the bearing chamber. This problem is obvious on the high-voltage motor, Ms. Shen once did a test, the highest point of the bearing cover temperature is 10K higher than the lowest point, open it to check, the grease at this position is indeed more accumulated.

● The stator and rotor rub each other, which is what we call sweeping, when the stator rotor is rubbed, it will not directly cause the motor not to rotate, but the motor loss will increase significantly.

● The axial size of the rotor is incorrect, causing both ends to die and making the rotation inflexible.

● Components such as oil seals or water throw rings are installed incorrectly or deformed, resulting in large frictional resistance.

● With fan motor, the fan rubs against the related parts and causes poor rotation.