Briefly describe the four principles of motor design!
A motor is a device that converts electrical energy into magnetic energy and then into mechanical energy. So the core inside is electromagnetic conversion, which is the calculation of circuit and magnetic circuit. The drawings are only external manifestations. The real designers should design and calculate the circuit and magnetic circuit of the motor, calculate the size of the stator, the number of coil amps, the air gap flux and other important parameters......
1. Do not design a motor that is too slender or flat
The motor design strives to achieve optimum performance with minimal material and cost. In general, flat motor effective materials use less iron and more copper. More structural materials. The slender motor has more iron for its effective material. Less copper, less structural material, but the rigidity of the structure is poor.
Therefore, the ratio of the diameter to the length of the motor has an optimum value. The ratio of the inner circle to the length of the core is about 1:1. The design of the motor should be optimized according to the various performance requirements of the motor and the effective materials and structural materials on the market. In addition, the serialization, the generalization of the components, the structural process, the cost of the tool and the mold should be considered.
2. The current density of the coil should not be too large or too small
The motor coil has a certain resistance, which causes loss when current passes through the coil, which reduces the efficiency of the motor and increases the temperature of the winding. The motor is designed to reduce the resistance to reduce losses, reduce temperature rise, and improve efficiency. Reducing the current density and increasing the cross-sectional area of the wire can reduce the resistance, but will result in an increase in the amount of coil material. As the groove area increases, the core magnetic density increases, and the excitation current and the iron loss of the motor increase. Therefore, the choice of current density should fully consider the performance of the motor. The current density is generally selected from 3 to 7 A/mm2. For small motors and closed motors take small values. For small motors and open motors, take large values.
3. The core magnetic density should not be too high or too low
When the core material, frequency and thickness of the silicon steel sheet are constant, the iron loss is determined by the magnitude of the magnetic flux density. The magnetic flux density is too high, the iron loss is increased, the motor efficiency is lowered, and the iron core heating causes the temperature rise of the motor to increase. And because the excitation ampoule increases, the motor power factor decreases. Therefore, the magnetic flux density of the iron core should not be too high, so try to avoid using the supersaturation section of the magnetization curve. Small motors generally do not exceed 155T. If the magnetic flux density is too low, the amount of motor material is increased and the cost is increased.
4. The slot full rate should not be too high or too low
The chute full rate refers to the ratio of the area of the wire in the slot to the effective area of the slot. The large tank full rate means that the tank is tightly packed and the tank fullness is small, indicating that the tank is filled loosely. In terms of the full utilization and operating performance of the motor material, the higher the tank full rate, the better. However, it is difficult to over-insert, the labor and working hours increase, and it is easy to damage the insulation. The slot full rate is low, the wire is loose in the slot when the motor is running, and the insulation is easily broken. In addition, there are many gaps in the slot. Due to the poor heat conduction of the air, the heat dissipation of the coil is affected, and the temperature rise of the motor is increased. Manual fillet slot full rate is generally 75% to 78%, not more than 80%. For automated rules, the general slot full rate is no more than 75%.
