2. Verification of high-efficiency motor design effects
2.1 Increase effective materials to improve motor efficiency
There are two aspects to adding effective materials: one is to increase the motor copper,
The amount of aluminum is used to reduce the stator and rotor resistance; the second is to use higher performance materials, such as high-performance silicon steel sheets to reduce iron consumption, and cast copper rotors to reduce rotor copper consumption. Table 1 shows the loss and effective material usage of four 45kW-2 motors that meet Class 3 energy efficiency and Class 2 energy efficiency. It can be seen from the data in Table 1 that the increase in efficiency is mainly due to the reduction of copper loss and iron loss on the stator and rotor sides, and the copper loss on the stator side, the copper loss on the rotor side and the iron loss are reduced by an average of 20% to 30%. Combined with the data in Table 1 and the design and manufacturing process of these motors, the following measures are taken to improve the efficiency of the motor.
(1) increase the length of the core and increase the cross-sectional area of the winding
The energy efficiency of the 45kW motor level 3 to the level 2 energy efficiency core length increased from 200mm to 230mm, and the length increased by 15%. In the case of satisfying the same magnetic load, the increase in the length of the core can reduce the number of turns of the motor, thereby increasing the cross-sectional area of the single-turn coil and reducing the stator resistance.
(2) The use of higher performance silicon steel sheets uses silicon steel sheets with lower unit iron loss and better performance. When the core length is increased, the total iron loss is reduced.
(3) Enlarging the groove size and increasing the amount of copper wire and cast aluminum. The energy efficiency of the second-grade energy efficiency is increased by 22.4%, and the amount of aluminum is increased by 6.9%, which directly leads to the stator and rotor. The reduction in resistance.
2.2 Improve the process to improve the efficiency of the motor
The prototype was fabricated by punching out the air gap process of the motor and compared with the ordinary motor. The comparison results are shown in Table 2. The four 22kW-4 prototypes in Table 2 are designed according to Class 2 energy efficiency (ie IE3, 93%). The No. 1 and No. 2 prototypes use the punching air gap, and the No. 3 and No. 4 prototypes are used for turning. Air gap. It can be seen from Table 2 that the stray loss of the No. 1 and No. 2 prototypes is much lower than that of the No. 3 and No. 4 prototypes, and the average is about 30% lower, indicating that the method of directly flushing out the air gap reduces the spurs. The loss effect is obvious.
After the cold-rolled silicon steel sheet is punched and sheared, the edge of the punching-shear separation line causes internal stress accumulation and physical property changes due to plastic deformation, resulting in lower magnetic permeability and increased iron loss of the cold-rolled silicon steel sheet, which makes full use of cold rolling. The excellent magnetic permeability of silicon steel sheets brings disadvantages. Choosing a suitable annealing process can eliminate the shear stress and restore the performance of the cold rolled silicon steel sheet. Special experimental research was carried out on the die annealing process of several specifications of motors. The performance comparison is shown in Table 3. It can be seen from the comparison that the iron loss of the annealed motor is smaller than that of the unannealed motor, and the power factor of the motor is also improved due to the recovery of the magnetic properties of the silicon steel sheet.
2.3 Using low harmonic windings to improve motor efficiency
Using self-developed electromagnetic calculation software, we have performed winding modification on several specifications of the motor. After using double-layer concentric unequal windings, the harmonic content is greatly reduced. Taking a 110kW-4 motor as an example, the variation of harmonic coefficients before and after the winding change is shown in Table 4. It can be seen from Table 4 that after the double-layer concentric unequal windings, the fundamental wave coefficient is 98.8% of the original, the change is not large, and the other subharmonic coefficients are greatly reduced. The reduction in higher harmonic content can reduce the stray losses of the motor.
The use of the concentric winding rear end can be shortened, saving the amount of copper wire. See Table 5 for the change in copper amount before and after the winding modification. The end of the 110kW-4 motor is not intentionally shortened, which can save 6.3% of the copper wire, while the 15kW-6 motor and the 55kW-2 motor shorten the end and slightly adjust the wire gauge, saving about 10% of the copper wire. .
The test data of the prototype using the low harmonic winding and the common winding prototype are shown in Table 6. By comparing the test data in Table 6, it can be seen that after using the low harmonic winding, the stray loss is reduced by 40% to 50%, and the efficiency is improved by 0.4 to 0.7 percentage points. By rational design, the ordinary winding is replaced by a low-harmonic winding, which can reduce the stray loss of the motor and improve the efficiency of the motor while saving the cost of the motor. The energy-saving and efficiency-increasing results are very obvious.
