In the inspection of the motor, it is often found that the performance indicators of the sample during the product trial identification meet the drawing and product requirements, but in the production of different manufacturers or the same manufacturer, the product performance of different batches fluctuates greatly, and the analysis is caused by the instability of the design and manufacturing quality of the chip and the iron core. This paper describes some potential problems which affect the performance and are difficult to find in the design and manufacture.

In the years of motor research and development and production process often found that the motor according to the same product standard, the same electromagnetic design of the motor products between its efficiency, power factor, no-load current and temperature rise, vibration, noise, etc., there are large differences, designers because of the type test after the design did not make any changes and this is also at a loss, puzzled. After relevant investigation and in-depth analysis of different manufacturers, different production processes and different batches of product test results, the impact of punching on motor performance, punching size is given by design, and the process of motor punching is generally obtained by wire cutting, mold, manufacturing factors affecting quality.

The loss and magnetic permeability of silicon steel sheet, the magnetic permeability of silicon steel sheet of different batches of the same manufacturer, the specific loss performance is not exactly the same, although there are standard values, but they fluctuate within a certain range. If the amplitude of fluctuation is relatively large, or the material of the silicon steel sheet itself does not meet the requirements, then such a silicon steel sheet is used on the motor, which will greatly affect the motor performance, especially for medium and large motors, the iron core transformer consumption accounts for a large proportion of the loss, and the impact on performance (mainly temperature rise, power factor) is also more detailed. The insulation between the silicon steel sheets can inhibit eddy currents in the core, thereby reducing the resulting eddy current loss (which is included in the iron loss). The insulation layer between the sheets is formed in the following three ways :(1) the insulation between the sheets is formed by the paint film of the cold-rolled silicon steel sheet; (2) The motor manufacturer applies insulating paint on the blanking film without paint film; (3) The hedge sheet is oxidized in the motor manufacturer to form an insulating layer.

The influence of the iron core overlaying is not only the increase of the temperature rise of the motor due to the increase of iron loss and no-load current, but also the decrease of efficiency and power factor. The influence of irregular iron core is mainly due to the excessive burr of the punching plate, the deviation of the die and the operator's not fine core, its harm: (1) iron loss, no-load current increase, the impact on the performance is as above; (2) The outer circle of the iron punching is not neat, and the temperature rise increases for low-voltage motors based on heat conduction and heat dissipation; The rotor core and the iron core have the same harm caused by poor laminated quality.

The design and manufacturing quality of the iron power core not only affect the electrical and mechanical properties of the motor, but also are closely related to the manufacturing cost of the motor, and such quality problems are not easy to be detected in the manufacturing process. In order to stabilize product quality, some effective "gatekeeping" measures should be taken in the design process, strictly according to the design and process requirements, control the punching and iron core manufacturing quality, and ensure that product quality meets the standard requirements. Designers in the design of stamping, iron core, first to take into account the processing technology, so that product quality tends to be stable; The second is to notice the hidden problems that have an impact on the quality and are difficult to find on the calculation list.