I would like to discuss with you today some small knowledge of the iron core manufacturing process, as well as some principles and precautions. In order to make a better product, I think it is necessary to discuss with you, welcome to supplement.
Iron core is one of the effective parts of the motor. The manufacturing process of iron core has a great influence on the performance of the motor. Iron core manufacturing process includes punching sheet manufacturing and iron core compression. Punching of the sheet belongs to the stamping process. Today, we introduce the type and application of iron core punch material, general problems of stamping process, and then explain the quality inspection of iron core punch piece manufacturing, iron core pressing, iron core creation and its impact on product quality.
Due to the high permeability of soft magnetic materials, low hysteresis loss and easy to manufacture, iron cores are generally made of soft magnetic materials. The varieties of soft magnetic materials include common carbon structural steel, Silicon steel sheets, electrician pure iron, and magnetic conductivity alloys. In addition to the general carbon structure steel plates commonly used in the magnetic core of DC motors and synchronous Motors, the most commonly used material for motor iron core punching sheets is Silicon steel sheets, and some motors also use electrician pure iron or conductive magnetic alloys(such as ferronickel alloys)., iron pan and other gold).
The thinner the Silicon steel sheet, the smaller the loss of the iron core, but the lower the mechanical strength of the punch sheet, the increase in the manufacturing hours of the iron core. After stacking, due to the increase in the proportion of the insulating thickness of the punch piece, the overpressure coefficient of the core is reduced, resulting in a decrease in the effective length and cross-sectional area of the core. Therefore, it is not appropriate to use a thin electrical steel strip(sheet) in the moderate electrical mechanism, and the thickness usually used is 0.5 mm and 0.35 mm.
The operation of the iron core of the motor is sometimes a normal phenomenon. For example, it is normal for the heat in the operation to reach 50 °C at an ambient temperature of 30 °C. During the normal operation, there are losses, mainly iron losses, copper losses, and mechanical losses. These losses are converted into heat, which increases the temperature of the motor.
The main reasons for the heat of the motor core are as follows:
1, the effect of voltage changes on performance
When the power supply voltage is too high or too low, it will cause heat. For example, when the voltage of the power supply drops, the starting torque will drop in proportion, causing the starting time to be extended. In serious cases, the motor can not even be started and the motor is burned. This is even more prominent in the use of overloaded starting and frequent starting. When the power supply voltage rises, it will increase the saturation degree of the motor's magnetic circuit, causing the current to increase and the temperature to increase. Therefore, the voltage fluctuation range of the power supply should be strictly controlled within the allowed range to ensure normal operation.
2, the effect of voltage asymmetry
When the voltage of the power supply is asymmetric, a negative sequence rotating magnetic field will be generated in the motor, and its effect on the performance and life of the motor is greater than that of voltage and frequency fluctuations. The degree of voltage asymmetry can be expressed by the voltage imbalance rate. A small unbalanced voltage will cause a relatively large unbalanced current, so that the current of a certain phase of the stator is greater than a larger value of the rated current. The unbalance rate of the three-phase voltage requires no more than 1.5 %. When it is greater than 3 %, the loss of the motor will increase by 20 %, causing overheating of the winding, accelerating insulation aging, and even causing failure.
3, motor failure caused by the heat
The motor is in operation and will fail due to various reasons. Common faults mainly include: winding short circuit or grounding, iron Silicon steel insulation damage, motor overload, winding lack phase operation, bearing damage caused by motor bearings overheating and so on. When these failures occur, it may cause the motor to overheat.
4, mechanical overloading causes motor overheating
When the motor is overloaded, especially when it is overloaded for a long time, the current of the motor will increase, causing the motor to seriously overheat and burn.
5, ventilation heat loss caused by motor heating
The ambient temperature around the motor is too high, the ventilation channel of the motor is blocked, the oil mud in the motor, and too much dust will affect the cooling effect. Therefore, the ambient environment around the motor should be ensured to be clean, the cooling conditions should be improved, and the temperature of the motor should be reduced.
In the process of using the iron core of the motor, it is necessary to find the root cause in time and take measures in time to ensure normal production.