How much do you know about these 26 cases of motor design taboos?
1, coil current density should not be too large or too small: motor coil has a certain resistance. When the current through the coil will produce loss. Winding temperature rise, motor design hope to reduce the resistance to reduce losses, improve efficiency. Thickening the wire diameter and lowering the current density can reduce the resistance, but it will increase the amount of coil material used. Due to the increase of slot area, caused by the core density increases, so that the motor's excitation current and iron loss increases. Usually induction motor j take 3 ~ 7A / mm ² (slot area is large, that is, the chip design of the core slot hole is large)
2, the motor core flux density should not be too high or too low. When the core material, frequency and silicon steel sheet thickness of iron loss is determined by the size of the flux density Ø, flux density is too high to increase iron loss, motor efficiency is reduced, the core heating motor temperature rise. And due to the increase in excitation ampere-turns motor power factor decreases, so the flux density of the core should not be too high, try to avoid using in the oversaturation section of the magnetization curve, the magnetic density is too low so that the motor material usage increases, the cost increases. Chip teeth are narrow, high magnetic density that is slotted into the line of the empty space is also a large core slot hole and vice versa.
3, motor slot full rate should not be too high or too low. Generally take 75 ~ 85% slot full rate of low motor running wire loose in the slot. Easy to damage the insulation. In addition, the slot gap more, due to poor air thermal conductivity, affecting the coil heat dissipation so that the motor temperature rise.
4, the design of the motor slot shape as far as possible to use parallel teeth trapezoidal groove and groove edges do not have sharp corners, as far as possible with a round bottom groove, due to the round groove casting of aluminum filled with a good, and do the mold is convenient. Stator chip embedded line is easy.
5, the motor slot width should not be too large, the slot is too large Ambassador air gap flux distribution is not uniform, tooth harmonics increase additional loss increases, usually about 3.5mm, too small into the line is difficult, the stator chip embedded line.
6, the number of stator slots should not be too many or too small. Asynchronous motor stator slots more, magnetic potential, potential waveform, additional loss is small, high efficiency motor slots more also make the coil and core contact area increases, coil heat dissipation is good, low temperature rise. Good performance but difficult production process. High cost
7, asynchronous motor air gap, magnetoresistance, excitation ampere turns, so that the motor excitation current increases, the motor power factor decreases, but the air gap Ambassador harmonic magnetic field is weakened, the motor additional loss decreases, the air gap is too small easily caused by stator-rotor sweeping, as well as due to the increase in the additional loss of the motor efficiency decreases.
8, asynchronous motor rotor torsion can make the rotor guide strip along the axial harmonic potential phase is different and weakened, thus reducing the additional synchronous torque, and additional asynchronous torque, reduce the additional motor losses, improve efficiency, reduce noise, vibration.
9, single-layer winding should not be used for larger capacity motors, smaller capacity motors do not double-layer winding.
10, large motors should not use aluminum alloy bracket due to the stiffness, strength is poor.
11, try to avoid the use of different widths of the keyway on the shaft (i.e., meson groove) core secondary position should be chamfered.
12, both ends of the motor with rolling bearings axial do not jam. Because when the motor is running the heat dissipation of the rotor shaft than the stator bracket is poor, the temperature rises some, the rotor shaft of the thermal expansion is greater than the stator parts, and bracket, seat. The rotor shaft can not be free to expand, so generally add the wave meson plus beer Ling cover.
13, the length of the rotor shaft and rotor chip with not too long. (The center part of the core can be reduced to solve)
14, with rolling bearing structure do not make the motor rotor to produce axial runout. (So the beer order within the wave meson) Sliding bearing in the front of the rotor with a curved meson Portable vacuum machine without curved meson is the front end is E meson structure of the false position control is very small 0.1 ~ 0.4mm
15, the motor's stator, rotor core should not be dislocated, dislocation of unfavorable reasons a: dislocation is equivalent to the effective area of the air gap decreases, the excitation current increases, the power factor decreases. Also make stator current stator copper loss, low efficiency. Temperature rise. B: The rotor is subjected to an axial force to accelerate bearing wear. Increase the noise and vibration of the motor. (But some finished products run to the front end of a direction often grinding one end of the bearing at this time deliberately misaligned) c: affect the normal ventilation of the motor.
16, pay attention to the asynchronous motor rotor cast aluminum quality (available sulfuric acid to dissolve the chip to see)
17, the lead should not be too thin if the lead is too thin easy insulation aging usually conductor current density of 4 ~ 6A / mm ² small motor to take a large value. Large motor to take a small value.
18, motor starting current is generally about 6 times the rated current, so do not start frequently, blocking the current Fish is usually 2.5 ~ 3 times the rated current. Current Fish need 200% of the current to break.
19, the critical rotor speed should be greater than 1.2 times or less than 0.8 times the rated speed to avoid resonance.
20, the motor should be dry to avoid a sharp rise in temperature. Excessively humid windings, should be avoided with the current into the method of drying.
21, stator groove wedge should not be higher than the inner circle of the iron core.
22、Dismantle the bearings into the bearings should be put force on the inner ring, can not force the outer ring and steel ball bit.
23, dusty places do not use protective motor application closed motor. (But closed motor is not easy to dissipate heat.
24, do not be motor in the power supply frequency is too low operation. When the power supply voltage is certain, the frequency decreases so that the flux increases, the motor design generally make the silicon steel sheet work in the saturation area of the magnetization curve, the flux increases so that the excitation current increases more, the power factor decreases, the motor current increases the copper loss increases, the efficiency decreases, the frequency decreases also make the motor speed decreases. Reduced airflow, heat dissipation difficulties, motor temperature rise. Decrease in power frequency not only reduces the output power of the motor, but also makes the performance worse. Rated frequency can not exceed 1%
25, do not make the power supply voltage of the asynchronous motor is too high or too low. If the voltage is too low, the magnetic flux of the motor will be reduced, and the torque of the motor will decrease in proportion to the square of the voltage. Caused by electric starting difficulties, the motor load is unchanged when the motor current increases, loss increases, temperature rise increases, low voltage operation for a long time may make the motor burned.
26, commutator and carbon brush friction noise. Because a commutator surface processing accuracy and roughness is poor. b. Carbon brushes and brush box clearance is too large. c. Carbon brushes spring elasticity failure. In addition, there are debris on the surface of the commutator is easy to produce sparks.
