The determinants of motor core quality and its relation to motor performance

02 Jan 2024
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GNEE Steel Cold rolled grain oriented silicon steel
The electrical steel punching material and punching quality of the stator and rotor core of the medium and small cage three-phase asynchronous motor directly affect the core quality, and the iron core quality affects the comprehensive performance of the motor. The irregular shape of the iron core affects the winding embedment, the burr is too large, and the accuracy and tightness of the iron core size affect the magnetic conductivity and loss. Therefore, ensuring the manufacturing quality of the punching and laminated core plays an important role in improving the quality performance of the motor.

Punching quality is related to punching die structure, punching equipment precision, punching process, punching material mechanical properties and punching shape and size. The dimensional accuracy, coaxiality and slot position of the punching sheet are guaranteed by the electrical steel sheet punching die, punching scheme and punching machine. Reasonable clearance and die manufacturing accuracy are the primary conditions to ensure the accuracy of punching size. The technical conditions stipulate that the precision difference of the stator tooth width is not more than 0.12mm. The control of punching burr, the clearance of the die is too large, the die is installed incorrectly or the die edge is blunted, and the punching will produce burrs. Strictly control the gap between the punch and the die during mold manufacturing, ensure that the edge clearance is uniform during installation, timely trim the cutting edge, and ensure the normal operation of the die during punching, which can effectively reduce burrs. The burr is too large, easy to cause short circuit between the iron core chip, increase the iron consumption and temperature rise. Excessive burrs in the stator slot may puncture the winding insulation and cause the slot teeth to swell. The burr at the shaft hole of the rotor is too large, which can cause the size of the inner hole to be reduced or the roundness to be out of line, making it difficult to press the iron core on the shaft.
Oriented Silicon SteelGrain oriented silicon steel
The main quality problems of the stator core are: the iron core is not compacting, resulting in the core is too long: the weight of the iron core is short; The iron core is round inside, but not round outside. The stator core length is greater than the allowable value, and the stator punching burrs are too large, which may cause the stator core teeth to spring open, the effective length of the air gap to increase, the air gap magnetomotive force to increase, and the stator current to increase. The lack of the weight of the stator core reduces the net length of the stator core, the cross-sectional area of the stator teeth and choke, and the magnetic flux density increases. The stator punching burr is too large, the thickness of the electrical steel sheet is uneven, the punching sheet is rusty or stained with dirt, and the pressure during pressing is not enough, which will cause the lack of iron core weight. The stator core is uneven, the outer circle is uneven, and the outer circle of the stator core of the enclosed motor is not in good contact with the inner circle of the frame, which affects the heat conduction and the temperature rise of the motor. The inner circle is not uniform, not grinding the inner circle, there may be fixed and rotor core friction, destroy the groove insulation, grinding not only increases the working time, but also increases the iron consumption. In order to improve the manufacturing quality of round and iron core, the following control measures can be taken: improve the manufacturing accuracy of die and ensure the punching size; To achieve single machine automation, so that the punching sequence is stacked in a straight direction, press assembly: to ensure the precision of the process equipment used in the stator core press assembly, such as mold, groove sample rod, etc. : to strengthen the quality inspection of each process during the punching and iron core pressure process, and strictly control the quality of parts.

The quality problems of fixed and rotor core are hidden in the manufacturing process. In order to stabilize product quality, effective measures should be taken in the design process, strictly according to the drawings and process requirements, control the punching and core manufacturing quality, and ensure that product quality meets the standard requirements. In the design of stamping, iron core, we should pay attention to the adaptability of the processing technology, but also pay attention to the inherent quality of the material, so that the product quality is more stable.
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