With the development of industrialization, the demand for electric motors in the global market is increasing.
High-efficiency electric motors are directly related to energy-saving and emission reduction policies, and many national key projects and municipal projects must have IEC energy efficiency assessment requirements for bidding electric motors, especially those entering European countries through exports.
However, for electric motor manufacturers, the improvement of electrical motor efficiency is a very important matter, which requires certain professional skills, such as the determination of losses, the determination of key factors affecting electric motor efficiency, the causes of losses and quantitative analysis for the peak performance .
Let's start with the causes of increased losses, and break down and analyze them one by one
Large stator copper loss
● High resistance of stator motor windings.
(1) Large wire resistivity or small wire diameter, uneven wire diameter or less number of parallel winding roots.
(2) Wiring error or poor welding.
(3) The actual number of turns is more than the design value.
● High stator current.
(1) Other losses are large.
(2) Asymmetry of stator motor windings makes the three phases unbalanced.
(3) Serious uneven air gap of stator and motor rotors.
(4) The resistance will be less than the normal value at this time because the number of turns is less than the normal value.
(5) the winding wiring is incorrect.
Large rotor copper loss
● Rotor winding (or guide bar) resistance is large.
(1) the resistivity of aluminum (copper) is large.
(2) cast aluminum rotor guide bar or end ring inside the air with air holes or impurities, or due to casting defects resulting in local problems with thin bars.
(3) the stator slot is not neat (manifested as slot serration), there is a wrong piece, anti-piece, resulting in the effective area of the motor rotors slot is not enough.
(4) because of improper selection of casting parameters leading to the loose aluminum organization, which directly leads to increased resistivity.
(5) material does not meet the requirements, such as ordinary aluminum rotors using alloy aluminum.
(6) using the wrong rotor, etc.
● High rotor current.
(1) Using the wrong rotor.
(2) Using the wrong aluminum when casting aluminum, such as using ordinary aluminum for alloy aluminum rotors.
(3) Rotor core lamination is not solid, resulting in a large area of aluminum between the pieces into the rotor, resulting in excessive rotor transverse current.
Stray Large losses
● Improper selection of stator winding type or pitch.
● Improper selection of stator and rotor slot fits.
● Too small or seriously uneven air gap.
● Severe short circuit between rotor guide and core.
● Stator winding end is too long, etc.
Large iron loss
The poor quality of silicon steel sheet or the use of the wrong material.
such as 600 material mistakenly used as 800 for such degraded grade use.
For the outsourced cores, the motor factory should pay special attention to the problem.
Poor insulation between stator core pieces.
(1) No insulation treatment or poor treatment effect.
(2) The pressure is too high when the core is stacked, so that the inter-sheet insulation is damaged.
(3) Short circuit between core piece and piece when turning the stator bore or repairing and filing the core (the problem exists in most of the core manufacturing plants).
● Insufficient number of core pieces and insufficient iron weight.
(1) the Insufficient number of code pieces (missing pieces).
(2) The stacking pressure is small and not compacted, as a direct result of which the iron weight is insufficient.
( (3) Large burrs in the punching sheet, 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 motor failures problem of the silicon steel sheet.
● The magnetic circuit is too saturated, and the no-load current vs. voltage curve is bent more seriously at this time.
● No-load stray loss is large, because it is included in the iron loss during the electrical power test, making the iron loss appear larger.
● When the winding is removed by fire or electric heating, the core is overheated and the magnetic conductivity decreases and the inter-piece insulation is damaged.
This problem mainly occurs when the winding is removed by fire after a winding failure; some electrical motors manufacturers have sought a way to remove the winding by soaking it in lye.
High mechanical loss
● Bearing or bearing assembly quality is bad, at this time the motor shaft will be seriously hot or inflexible in rotation.
● Wrong external fan (such as 2-pole motor using a 4-pole fan) or wrong fan blade angle; according to the conventional design, the fan of 2P motor is relatively small, and the method to reduce the loss by adjusting the fan method is very effective, but the premise is to ensure the temperature rise performance of the electrical motors.
● The housing and the two end cover bearing chambers are not on the same axis.
● The bearing chamber diameter is small, which makes the outer ring of the bearing deformed by pressure and causes the bearing friction loss to increase; the situation of electrical motor parts may also lead to overheating failure of the bearing at the same time.
● Too much grease or bad quality of grease in the bearing chamber.
The problem is obvious in the high voltage motor, one of our engineers has done a test, the highest point of the bearing cover temperature is 10K higher than the lowest point, open and check, the grease in this position is indeed more accumulation
● The stator and rotor are rubbing each other, which is what we call sweeping.
When the stator and rotor are rubbing each other, it is not so much that it directly causes the electrical motors not to rotate, but the loss of the electrical motors increases obviously.
● The electrical rotors' axial size is incorrect, causing the top dead at both ends and making the rotation inflexible.
● Parts such as oil seal or water dumping ring are not installed correctly or deformed, resulting in large frictional resistance.
● Fan motor with fan, the fan rubs against the associated parts, resulting in poor rotation.
There are many factors that affect the quality of product, which is why when we purchase electric motor, we should always look for the professional electric motor manufacturer.
There are many information about the electric motors.
The above is my summary of some knowledge, if you have anything to add, welcome to leave a message in the comments section.
Dongchun motor is a professional manufacturer of electric motors in China.
Please kindly check the proudcts as follows
single phase motor : YC, YCL with cast iron body and ML , MY motor with Aluminium body
Three phase motor : IE1, IE2, IE3 motor for both cast iron body and Aluminium body
Brake motor: DC brake motor and AC brake motor
VFD motor : frequency variable drive motors.
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