Contents:
1. Overview of technical trends in electric drive systems
2. Drive motors
Chapter 1 Electric drive system technology trends
1.1 The New Automobile and the Internet of Everything
(This section is compiled from the speech of President Zhao Fuquan of Tsinghua University)
Only hardware is a walking corpse, only software is a lonely soul, only the combination of hardware and software can achieve the sublimation of the soul.
The automobile industry is turning into a new industry with the participation of energy industry, urban construction, transportation road and information industry.
Some people call it a brand new ecology, some call it a new enterprise, some call it a new energy car, some call it an intelligent networked car, but I prefer to call it a new car. The changes that the new car will bring to the whole society can no longer be seen simply from the perspective of transportation tools, but from the human flow, logistics, energy flow, value flow, and coupling through information flow, to achieve a radical change in the whole human society.
Into the new automotive era, hardware is as important as ever, only hardware is not enough, software becomes more adequate, and many of these technologies are hardware companies do not have the means to fully own, if you want to fully own, Toyota will become Huawei; if as ICT companies if all build hardware, it also becomes Toyota, if Toyota + Huawei divided by 2, may be equal to the chicken ribs. Internet of everything is the means, the actual circulation of data, so data is the basis, data to carry out in-depth processing, to produce intelligence, so that the same hardware to better serve humanity.
In the era of new automobile with everything connected, the hardware of automobile is a necessary condition and the software is a sufficient condition. The most important feature of the new automobile is that it is alive and can evolve, evolving by data and relying on AI for deep processing of data, constantly surpassing itself and achieving better and better use. It is always new.
How does the new car evolve? The immediate stage is electrification, and the next stage is intelligence. The next stage is intelligence, and the final realization is ecology.
Intelligence is the core competitiveness, the interconnection of everything is the means, the purpose of the connection is to circulate data, and the deep processing of data makes the whole society enter into a new era. The deep processing of data enables the whole society to enter the era of high level intelligence.
1.2 Development trend of electric drive system
The challenge of electric drive, the requirements of power density is getting higher and higher, the requirements of accuracy is getting higher and higher, the requirements of efficiency is getting higher and higher, in addition, to be able to adapt to different road conditions, but also the use of advanced multi-functional control module, to have high-performance power semiconductor power electronics converter, to have high-performance materials, including high-performance magnetic materials and high-performance super wire.
In addition to be able to do better with the policy, that is, how to do better with the vehicle in terms of mechanical, electrical and thermal interfaces. The first half of the Yangtze River Delta epidemic, the reason for the impact, from the data point of view of the cumulative volume of electric drive assembly is 2.138 million sets. From the segmentation of the market, the top three are Freddy Power, Tesla and Japanese trams.
This year the electric drive is expected to exceed 5.5 million sets, this year the flat line motor will exceed 2.5 million units. All-in-one integration or not there are still differences, A0 class and A00 class to control the cost of the main, in the form of two-in-one stand-alone more, A0 class all-in-one is the main, now is the mainstream of three-in-one, C class, D class above may be equipped with multi-shift. The cost of the corresponding supply chain is more mature, mainly in silicon carbide, the cost is relatively high, a few companies to achieve mass production. The entire electric drive, whether to improve efficiency or from all aspects is to reduce the overall energy consumption. Miniaturization, high-speed speed, more than 20,000 rpm of high speed technology, including a small reducer center distance, which has a means to effectively achieve miniaturization.
Silicon carbide module itself integrated application can make the size and weight of the motor controller can be further optimized. The two main indicators of electric drive system optimization is the power density and efficiency, to do new materials and new technology is to optimize these two technical indicators of the most effective measures. For example, high-performance permanent magnets, high-performance silicon steel, and multi-layer flat wire motors, wide band semiconductor, silicon carbide and gallium nitride use, are effective ways to improve these two performance indicators.
Optimizing the cooling system is also an important way to improve the two main indicators of the motor, and currently We have changed from water cooling to oil cooling, the next generation of cooling system may be more efficient than Such as air and water cooling technology, water as a medium than oil as a medium in the cooling efficiency is still The water as a medium is still more efficient than oil as a medium, and the air and water cooling is the first analysis of the hottest hot spots of the motor and inverter. Then, the hottest hot spots are built into the waterway by using the air-filled method, and then the water coolant is circulated in the The water coolant is then circulated inside to achieve the most efficient cooling.
1.3 High voltage, cost and power density
High voltage is the consensus of the industry, basically all electric drive companies have layout in high voltage, for high voltage, the first domestic publicity is Porsche, when the release of this product, the entire high voltage system, the parts are not very mature, the parts are retained 400V circuit. Voltage platform from 400V to 800V, although now the mass production models are not particularly, but everyone in the planning process or development projects inside the use of more, which faces great technical challenges, including voltage, including the core material heat dissipation capacity, including heat resistance. The technical challenges are great, including voltage resistance, including the heat dissipation capacity of core materials, including heat resistance. This year there will be a few brands of 800V products on the market. Take the A-class car as an example, the cost of the whole pure electric system, the motor accounts for 40%, the electric control is 40%, gearbox is 20%, if the motor is split, the whole silicon steel If the motor is divided, the whole silicon steel sheet is 40%, why many companies do non-magnetic, low magnetic technology pre-research.
The rest is some copper and processing and manufacturing costs, the overall view of the industry average price of independent brands of three-in-one is about more than 9000 yuan, 80-200KW cost is about 6000-12000 such a price range, now the overall will have some changes, especially silicon carbide this time the overall The price is going down, which is good information for us in terms of cost. Electric control is the core of the motor, IGBT accounts for a relatively large cost, about 44%, different models, the price of A-class cars IGBT is about 600-800 yuan, 200,000, 300,000 A-class cars IGBT is about 2000 yuan. Silicon carbide in this application in order to improve the relevant power density, the basic trend has become more obvious, with silicon carbide models and development has been no less than 10 models, silicon carbide from the entire industry chain of the entire development is not particularly mature, but also faces many related challenges, including some of the packaging materials will also affect the silicon carbide itself to achieve some performance. Increasing the speed of the motor is another effective way to improve power density and efficiency. At present, the speed requirement of the motor under research has reached the level of 18,000 rpm - 20,000 rpm, and the next generation of motor speed is likely to run towards the level of 25,000 rpm. Here there are some technical bottlenecks, on the one hand, the bearing of high-speed technology, and on the is the MCU, the chip's computing power, but also on the motor speed has a certain bottleneck role. Because we now motor speed to be high, the control frequency should be increased, the motor controller Operational efficiency, computing speed is also a big bottleneck.
1.4 Electric drive efficiency
Now the efficiency of the mainstream three-in-one electric drive assembly, in the 400V platform, the efficiency is in 85%, 86% or more, higher may have 87%, 88%, we calculate that if the next step combined with some 800V and other new technologies, if the three-in-one efficiency of the working conditions and then increase by three percentage points, such as to 90% or 91%, for the whole car range, and for the The cost reduction is very good for the user. For example, the cost of the whole car can be reduced by 4,000-5,000 yuan or even higher. Now more and more use of multi-layer flat line, and later need to be more accurate for more specific The car models, products, to make our electric drive working conditions interval to do a more accurate definition, and even Even the center of energy consumption of the whole system or the center of gravity on the MAP diagram should be better designed and defined in a positive way. The center of gravity of the whole system energy consumption or MAP diagram should be designed and defined in a more positive way.
The Arashi diagram is also being developed to use a disconnecting mechanism, especially for the 4WD models. We predict that with this disconnecting mechanism, the mileage improvement will be around 3%. The contribution of the disconnect mechanism is expected to be around 3%.
800V plus silicon carbide voltage upgrade measures, this may also contribute to the efficiency improvement of working conditions.
1.5 Changan Automobile all-in-one
In 2018, the first generation of Changan Automobile's electric drive is split, the second generation proposed "three in one", and now in the third generation, in 2020 Changan proposed called "super set of electric drive third generation", which is all in one, the power density continues to improve, efficiency All in 1, Chang'an Auto's newest product is the "Super Collective Drive 3rd Generation", which is all in one.
All in 1, Changan aims to integrate the motor, motor controller, transmission, OBC, DCDC, DCAC, PDU and other functions, and overcome the noise problem, EMC problem, thermal control, reliability technology bottleneck brought by high integration, and the overall has reached the industry leading level. Breakthrough in power electronics integration and performance deep coupling technology, from integration and beyond integration. Super integration technology brings super efficiency, working condition efficiency is increased by 5%, using high efficiency power devices, oil cooling system, etc., so that the working condition efficiency exceeds 90%, the highest efficiency of the assembly exceeds 95%, and the single vehicle 10 years 300,000 km emissions are reduced by 20 tons compared with fuel vehicles. Among them, the contribution of eight-layer flat wire winding, efficiency increased by 0.9% rotor double V topology configuration efficiency increased by 0.4%, ultra-low resistance wire makes efficiency increased by 0.1%, low resistance topology optimization makes efficiency increased by 1.3%, a total of 163 patents. The world's first micronucleus high spell pulse heating technology, with this technology, it can achieve -30 degrees Celsius environment to ensure power, -35 degrees Celsius charging time shortened by 35%.
Chapter 2 Drive motors
2.1 Basic innovation of motor
For example, if the vehicle has the demand of maximum speed, the motor has the requirement of maximum speed; if the vehicle has the requirement of range, the motor has the corresponding demand point of efficiency. In the past 20 years, the motor raw materials, the main raw materials, including silicon steel sheet, copper wire and magnets change relatively less. The silicon steel sheet over the years there has been little change in thermal conductivity, the enameled wire is actually just the strength of the enameled wire itself continues to improve, but the conductivity does not seem to have much progress. Magnet performance is also very difficult to improve, in fact, the light magnet performance is not useful, because the thermal conductivity of silicon steel is still limited, so the main material to improve the power density of the motor is actually very difficult. Motor principle is very difficult to innovate, only through the application of new materials and new processes, and constantly improve the power density of the motor and so on. At the same time, we also expect better insulation materials, hope that insulation materials not only insulation, but also thermal conductivity, which has a great practical demand, should also get some more technical breakthroughs. Some time ago, someone proposed to use super wire, super copper wire, the advantages of performance is relatively good The disadvantage is that at present it is too expensive, after the cost is reduced, the performance of the motor is improved It is indeed a great benefit, its conductivity can be increased by about 5%.
All technological advances must be the same cost to achieve higher indicators, or the same indicators to reduce costs. So the only way to improve the thermal conductivity, because after the thermal conductivity is improved, the temperature of the motor down, the performance of the magnets or copper wire conductivity, can be guaranteed. Of course, you can also use better cooling measures, but after all, there is cooling can not be cooled, there are better thermal conductivity materials to further reduce the temperature of the motor slot in particular, is very beneficial. After the adoption of BOOST, in fact, the voltage is variable, in this case, the overall efficiency is improved, because the motor can be designed more forward of the inflection point, the current is small when the small torque, high speed with voltage up, the power is enough, these two an integration, the efficiency improvement is very obvious. In response to the different needs of the vehicle, Huayu Electric now plans three flat-line motor platforms, internally called SD, HD and MD, which can cover the needs of traditional vehicles from A0 to C class, and these platforms can cover permanent magnet, asynchronous, high voltage, low voltage, water-cooled and oil-cooled, and the high speed here can reach over 20,000 rpm.
2.2 Flat wire motor
The advantages of flat wire motors are high slot full rate, good heat dissipation, high power density, high efficiency, round wire motors now the industry is 42%-45% slot full rate, flat wire can do 70% of the slot full rate. Due to the small thermal resistance wind in the slot of the flat wire motor, heat dissipation is good. And NVH performance is better, from the production point of view, the flat line relative to the round line of a higher degree of automation, can meet the relatively high production tempo. Production can be modular, now the last two years the domestic equipment process is becoming more mature, the domestic supplier capacity is also increasing, because the automation production efficiency is higher, resulting in the consistency of production will be stronger. For the flat wire motor, because the slot can be stuffed with more copper, the slot area can be reduced to improve its thermal load, power and torque will be improved. But the flat wire motor has its weaknesses, the main weakness of the flat wire motor is that the skin effect is more obvious at high speed, because the flat conductor cross-sectional area is larger, the larger the area the greater the skin effect, especially at the end near the slot opening, usually hotter. More than 15000 rpm round wire motor is better, because the domestic speed is relatively low, flat wire motor can play the road conditions advantage. Flat wire motors relative to round wire motors, because round wire we can often adjust the number of turns of winding resistance, flat wire motors do not have this aspect of the characteristics of the round wire winding can be flexibly adjusted, flat wire no room for adjustment, Founder through the air gap and material changes to match the rotor changes to flat wire motors platforming.
Founder's current mass production of flat wire motors, the basic parameters of the electronic flat wire is 205, the power can reach 4.8KW/KG. flat wire motor is a process innovation, from the original a round wire stuffed into the motor, replaced by a few strands of square wire, round wire and round wire is line contact, flat wire and flat wire is surface contact, so its power density increased, thermal conductivity improved, noise has also improved. There are also disadvantages, the disadvantage is that the investment cost is relatively large, the problem of loss is inevitable, does not mean that the original no loss. Flat wire motor first problem, AC losses in the case of high speed is relatively large, second, the number of conductors inside the slot is relatively small, trying to match some parameters is very difficult, flat wire motor in the use of 6 and 8 layer program, does not mean that the power density really increased, in fact, it brings two disadvantages, first of all, the more layers of wire, the gap between the wire and the wire, the proportion of the end of the wire varnish actually more, now the highest speed Run to 20,000, or even more than 20,000, do not use 12 layers or 16 layers? The more layers, in fact, the conductivity is decreasing, and in the end it is meaningless. The second is that this increase in the number of layers requires high investment in equipment, especially for phase change, and some companies have designed a more complex system, such a design will lead to poor flexibility and higher investment risk. EVK is developing the third generation of flat wire motor, its slot type is different from the original, the first role is to further effectively improve the power density of the motor, the goal is to increase by another 20%, EVK proposed a new slot type, because the traditional flat wire motor using equal slot block design, its magnetic is not equal block, the slot part is very saturated, not waste, so EVK proposed close to the equal magnetic block design The effect of this arrangement structure has also changed. The power density of EVK's core design is increased, and by analogy with a 220 diameter, 320 Nm motor, a round wire motor would be 140 long, but with the second generation, it would be 105, but with the third generation technology, only 80 mm is needed, and it can even be smaller. The whole development history of flat line of Huayu Electric, first from 2014 engaged in the research and development of flat line motor, in 2017 the flat line motor in domestic mass production, in 2020 the 8 layer flat line motor in domestic mass production, this year the 8 layer oil-cooled flat line motor officially achieved mass production. Flat wire motor and round wire motor they have their own application areas and space, but the flat wire motor applications to a wider range of fields.
2.3 High voltage 800V
Since last year, everyone began to talk about 800V, higher voltage corresponds to higher efficiency, whether through simulation or actual measurement, 800V efficiency for the motor has a significant increase in cost performance can be improved at the same time, because the power torque up, you can make the motor smaller, material costs can be reduced. High voltage motors are a big challenge for the insulation system, the constant voltage is 800V, the overcharge voltage can reach 1100-1200V, along with the partial discharge is relatively high, the insulation pressure of the motor is greatly increased, the existing insulation design is no longer applicable. The new insulation design requires a lot of verification work to achieve full coverage from parts to the whole motor. In order to adapt to the new insulation design, the production process and equipment of the motor also need to be readjusted to reduce the damage of the insulation layer during the production process. Flat wire process is stamping or bending, the damage to the enameled wire is different, after the selection of the process route based on different parts to simulate the process and then do the endurance of the single and aging test, the parts and process superimposed to verify. After passing, then go to do the DV test of the whole machine. After high voltage for the insulation system aging, such as thermal aging, mechanical, environmental, electrical these will be a challenge to the insulation system, high voltage system research methods, Huayu first from the study of materials, including electromagnetic wire, insulator, electrical gap, insulation materials. The impact of different processes on the copper wire is also different, Huawei carried out the verification of the motor, and then the verification of the whole vehicle, and finally came up with the technical specifications of 800V, at present, we do not have a very unified standard, all belong to their own in the study. High-voltage drive motor insulation system upgrade, the two technical lines have different schools, type 2 insulation system is better. Huayu Electric to 800V has now carried out some work, there is currently an 800V motor, is now doing the PV verification, is expected to be able to achieve formal mass production next year. There are some methods of shaft current design, the accuracy of the method needs some verification, through some simulation, the shaft current can be simulated at the beginning of the design, the principle is feasible.
2.4 Oil cooling technology
New energy drive motor has three basic cooling methods, wind, water, oil cooling, for A-class cars, the use of air-cooled may be more, for air-cooled motor we should be more clear, small size, light weight, heat dissipation is relatively poor, because there is no water and oil cooling, but indeed cheap, the cost is relatively low. Water-cooled is now used more, heat dissipation will be relatively better, the power density is relatively air-cooled to improve a lot. With the rapid growth of the price of rare earth materials in particular, oil cooling is becoming the trend of the entire power system. Cooling effect is better. Power density decreases, unit price increases, and material usage decreases. The advantage of oil-cooled system is good heat dissipation, in fact, especially recently, the price of gasoline materials and raw materials has increased, oil cooling can directly cool the rotor, magnets, especially for the rotor cooling effect is good, in the early stage to do very well, due to the heat dissipation capacity at high speed, its sustainability has been substantially improved; cost performance is more complex, because the oil-cooled system increases the heat dissipation capacity at the same time will also increase The cost of the entire system oil circuit accessories, this needs to be seen from the perspective of the market chemical materials, from the entire front of the material, the oil cooling system is not the best cost. Founder's oil-cooled system reduces the cost of magnets, compared to water-cooled magnets, the amount of rare earths is reduced by 50%. There are many challenges in oil cooling system, and there are very few oil cooling systems in the market nowadays, because the design of the oil circuit changes a lot, and it is necessary to adapt the whole system to achieve the best cooling effect. The whole oil circuit system is complex, involving not only the motor, but also the casing, gear box, oil pump, etc., and the requirement for cleanliness is relatively high, and the investment is relatively large. There are a lot of raw materials inside the oil-cooled motor and the oil will be chemically reflected and corrosive. The cost model has too many variables, and the variables have different stability in each time dimension, resulting in the whole system is changing in real time. For the 800V system, the first step is to reduce the voltage gradient so that there will be more options for insulation materials. Current experience shows that there is no way to reduce it completely simply by motor design, from the material point of view is two points, need high power resistance and high PDIV both combined together. On the other hand, the position and angle of the oil injection and the shape of some other oil nozzles, in fact, will have some impact on this, even we have to take into account the working environment of the whole vehicle, the change in the angle of the oil injection, in fact, will affect the cooling of the motor. The second is compatibility, compatibility is well understood, just said insulation insulation materials will have the impact of oil, there will be compatibility issues, so this said part is a challenge, different manufacturers OEM will use different APF, or even the same OEM will choose a different oil, so the insulation material selection verification has brought a great challenge. The third part is the cleanliness, before the water-cooled motor, the motor itself cleanliness requirements itself is not so high, now due to the use of oil-cooled all these foreign matter such as metal particles, non-metallic particles are in the oil circuit, non-metallic particles will affect the oil circuit blockage, metal particles may affect the motor short circuit, or that is more harmful some impact.
2.5 High speed
In the past one or two years, customer demand for speed is gradually increasing, and now there are more than 20,000 rpm, after the speed increases, the power density can be further improved. Tesla has mass production of carbon fiber rotor motor, now there are several forms of carbon fiber rotor, one is in the sheath set on the rotor, the benefit is relatively simple process in this part, but the performance requirements are relatively high, there is a direct winding way, divided into two, a dry method, a wet method, the wet method is a single carbon fiber wire bundle in the winding, one side in the winding, the other side in the dry joint material, but it is difficult to control the amount of some good places. But it is difficult to control the amount of some good places. There is another kind of process equivalent to the dry method, and the current dry process is easier to achieve in form. The first thing is to verify and test the material of carbon fiber itself. Now the carbon fiber rotor has been made and some endurance tests are being done. It seems that the test results are obvious, and the power and torque are improved after adding carbon fiber.
2.6 Hybrid power requirements and challenges for the motor
The first expectation of the hybrid system for the motor is that the size should be small, especially the axial size should be small, even if it is shortened by 1 mm, it is very valuable for the system. The hybrid system expects the motor cost to be low, the main cost of the motor is the metal material, it is unlikely that with a large amount of the cost will drop, to find ways to reduce the use of these materials is an effective way to improve the competitiveness of the motor. System extreme volume, not only to meet the system arrangement, but also the pursuit of the ultimate cost. After increasing the speed, the torque relative to the power goes down, and in this case, the cost goes down. But the same torque and power case, hope that the motor volume is small, if the speed of everyone is the same case, and then to increase the power density, only to increase the magnetic load and electrical load of the motor. With the saturation of the magnetic conductivity, in fact, it is difficult to improve the magnetic load, the motor's copper loss and iron loss and electrical load squared proportional, if the increase in electrical load, but more serious, of course, can be solved with better cooling, but also can not solve the motor's electrical density is too high resulting in low efficiency, improve the space utilization of the motor is a very good way to be able to the same torque speed Requirement of the case put more copper wire, although the copper wire did not come down, but can make other materials can effectively fall. Hybrid power is actually the most important source of energy or engine. In the low speed, the torque is relatively large, or if the Atkinson engine, it should be a little more torque in the middle speed of the high speed, which is the engine hopes to but the motor is afraid of high torque, because the high torque has a high current, after a high current will generate heat, if you want the generator to achieve high efficiency, the wire should be thick, so we need to increase the amount of copper as much as possible to reduce copper losses, is to improve Generator efficiency and engine efficiency to match the only way. For the generator, there must be inevitable PWM loss problem, the current silicon steel sheet can bind the current frequency of almost 2K, more than 2K is basically radio waves, radio waves to where to burn. Therefore, when considering the generator, we must pay attention to the PWM loss. First of all, design a reasonable inflection point to meet the power, as much as possible, the density is a little higher, I hope the system can properly reduce the power requirements, because the power requirements are large, the inflection point speed is high, the number of turns can not be more, of course, the inductance comes to a small, system efficiency is difficult to improve. Second, in the case of axial size allows, first use a small diameter motor, so that the effective length of the motor a little longer, because the filtering effect of the inductor is equal to two parts L. In this way, the external size is small, the resistance is small, the proportion of inductance is large, which is very conducive to improving the PWM harmonic loss. The third measure, we can do some PWM frequency conversion strategy on the control side, of course, these strategies are likely to bring other problems, but also can not guarantee that the PWM frequency are within 2K, can not meet the working range of so high, so this can only be optimized as far as possible to avoid some problems, but can not be the root cause. A relatively good measure is to add BOOST circuit on the controller, low speed on the low voltage, high speed on the high voltage, so that the inductor charging and discharging speed will be much faster, the PWM ramp control will be much better. Drive motor in the hybrid application, and in the pure electric is not the same, because our country pure electric according to CLTC conditions, the hybrid according to WLTC conditions. The biggest difference, the hybrid to run high speed, to run high 130 or more, to assess its fuel consumption, pure electric most within 120. Such a situation, the hybrid motor running 120 yards, the drive motor is not necessarily working, depending on the powertrain program, if you do not need the motor large torque output or relatively large power output, the motor is likely to be a drag on the system fuel consumption. How serious is the loss of 0 torque? Take 380 Nm / 14,000 rpm motor for example, we let this motor to simulation by 0 torque output, from low speed slowly run up, found that at the highest speed, its loss actually more than 5000 watts, corresponding to our common 120 yards of work, may be about 10,000 rpm or about 9,000 rpm, its loss is also very large, this loss where it comes from? Because most motors are now permanent magnet synchronous motor, there are magnets inside, rotating up to have iron loss. At the same time, the battery voltage in the case of limited, as the speed increases, the voltage of power generation is higher and higher than the battery voltage, this time to increase the speed, copper loss. So for 0 torque this problem, can't do effective control on copper and iron loss, will certainly be linked to the system. Calculated fuel-saving system, the result of running down the fuel consumption, most of them are also because of this reason. Hybrid high-voltage is mainly BOOST brings, after the high-voltage, most of all for the flat wire, it is likely that the same slot inside the two wires inter-turn voltage, this problem is very serious. If the two wires are broken, they can only withstand 500, 600 volts, for the BOOST boost, usually to 700, 800 volts, at least 600 volts. The risk is high in this case. Hybrid vehicle systems are very demanding in terms of space size, and the use of flat wire motors is the main measure of the current mature hybrid system. The generator and motor must not only realize the matching of high efficiency zone, but also pay special attention to reduce the PWM loss of generator and 0 torque loss of drive motor to achieve better fuel saving effect. EVK third generation flat wire motor technology has obvious advantages in the direction of axial space arrangement, high efficiency area matching and high speed and high voltage, which not only has certain cost advantages, but also can better help the system to achieve the relevant index.
2.7 Rotor position detection Rotor position detection solutions
Three main big technical directions: Hall sensors, continuous position sensors, and resolvers. The most common is the Hall sensor, which is to achieve 60 degrees of electrical angle commutation, the actual accuracy depends on the number of pole pairs, it is subject to mechanical design and assembly, so its accuracy can not be improved indefinitely, Hall sensor solution is mainly applicable to square wave drive. In terms of environmental tolerance, because Hall sensors are still mainly based on semiconductor components and PCBs, so its maximum environmental temperature is limited by the maximum operating temperature of the chip. If you do some thermal insulation design inside the motor is able to improve the resistance. Seismic performance is good. Another pain point, just mentioned based on PCB technology and semiconductor components, so if you encounter some special conditions, such as oil or gas into the motor interior, or some conductive or non-conductive impurities into the motor interior, about the oil and environmental pollution tolerance need to do special verification. Hall sensor electrical angle as well as mechanical angle accuracy is limited, while the continuous position sensor scheme can achieve a continuous position output, the interface is richer, including the three-channel Hall, can have a good interface. This solution also has corresponding assembly and design tolerances, but because this sensor will finally do an online calibration and programming, so its accuracy and errors in the assembly process can be compensated by the later calibration, so that a better accuracy can be achieved. In terms of environmental tolerance, it is the same as Hall sensors. Cost, because now more and more manufacturers to support the position sensor program, optional resources are still relatively abundant, but each manufacturer route is different, so in the application will encounter different problems and challenges, the overall comprehensive cost of hardware is slightly higher. Both Hall sensors and position sensors are based on semiconductors and PCBs, it is a relatively large pain point for the environmental tolerance of this piece. Rotary transformer can achieve high precision continuous position output, assembly accuracy can actually be controlled and compensated, because it can do some calibration and adjustment during the assembly process, in terms of environmental tolerance, its biggest advantage lies in the high tolerance and high reliability. Overall, it requires an external excitation source and corresponding coding and decoding circuits or chips and algorithms, and the combined cost of software and hardware is relatively high at the electronic level. Guangdong Textron Motor has done a comparison test, during the initial test, the average response time of Hall sensor motor is 5.19 ms, and the average response time of motor with position signal sensor is 6.03 ms, which is 0.84 ms slower, about 16% slower. Based on the analysis just done, the response of the position sensor has a significant effect on the response time, which is about 0.6 milliseconds. The oil seal characteristics of the shaft end, because this is related to the customer's energy consumption, can not be easily removed, but it will have a significant impact, add or not add, the impact on the response time is about 0.4 to 0.6. Then the grease characteristics and the control of the filling amount actually has a small impact, less than 0.1 milliseconds. After optimizing the design, improvement, and finally the actual test, the improved second generation motor, which is the position sensor motor, its average response time reached 4.74 milliseconds, for Hall sensor motor is 0.45 milliseconds faster, compared with the second generation motor before optimization is 1.29 milliseconds faster, before and after the optimization comparison, the dynamic response performance improved by 21%. The advantage of the rotary transformer is that it may deal with some special conditions, such as high temperature, high pollution environment, high vibration, especially there may be some for the electric field or magnetic field interference is relatively strong state, it will have a relatively good application advantage. Eddy current sensor is more like a resolver, except that the resolver is based on the magnetic field, while the eddy current is based on the electric field, the two are a similar program. Each program has its corresponding field and market, if more concerned about the cost to choose Hall, if there is a trade-off between cost and accuracy, to use continuous position sensing. If you use high reliability, go with a rotary transformer.
