Designing a brushless motor. Electric traction drive of a hybrid vehicle

21.04.2019

Piston aircraft engine VD-4K (M-253K).

Developer: OKB-36 (Rybinsk)
Country: USSR
Start of development: 1949
Built: 1950

M-253K (VD-4K) - Soviet aircraft engine combined type(turbocompound), made according to the block star scheme. The engine is a 24-cylinder block star (six blocks of 4 cylinders each).

The history of the combined VD-4K engine is not quite common and has its roots in the pre-war period. The fact is that they began to create it not in a specialized aircraft engine design bureau, but at one of the departments of the Moscow Aviation Institute. At the end of 1938, the then People's Commissar of Aviation Industry, M.M. Usually, the parameters of a new development in the field of engine building are selected on the basis of a long-term analysis of trends and future needs of our own aircraft industry, as well as the state of similar branches of technology abroad. M.M. Kaganovich, in general, not a bad person, but who got to the position for his devotion to ideas and leaders, a nomenklatura soul (today the director of the bathhouse, tomorrow the head of the Aviation Industry), being not very knowledgeable in all the intricacies of the “Preliminary selection of the main parameters for design", simply multiplied by two the data of the M-105 engine. Hence it came about that new engine was supposed to develop a power of 2100-2300 hp. at an altitude of 8000 m.

G.S. Skubachevsky with a group of students and graduate students worked out three layout options for a 24-cylinder engine: X-shaped, H-shaped and a kind of four-row star with six cylinders in each row. The last option turned out to be the most successful: its diameter was only 1065 mm, like the M-11 motor. It was assumed that a three-speed centrifugal supercharger would be used to increase the altitude, and the efficiency power plant raise the anti-rotation screws.

In July 1939, a government decree appeared on the design of the engine, called the M-250. A special KB-2 is being created at MAI, it is staffed from students, postgraduates and CIAM employees, teachers from other MAI departments were also involved. Design work began and already on April 1, 1940, the M-250 project was being passed by the Air Force Research Institute, a decision was made to build an experimental engine at plant No. 16 in Voronezh. The first launch of the M-250 at the stand was made on the fateful day of June 22, 1941. On tests, the engine showed the declared power of 2500 hp. Then sporadic work on the engine in the conditions of war and evacuation. They really returned to the topic in 1946, when a task was received for an engine with a capacity of 3500 hp for new heavy Tupolev machines. OKB-36 in Rybinsk under the leadership of V.A. Dobrynin, based on the theoretical and practical groundwork for the M-250, in a short time creates the M-251TK (VD-3TK) engine.

In January 1949, OKB-36 proposes, on the basis of the M-251TK, to create a new combined engine M-253K with a maximum power of 4300 hp. and with specific fuel consumption in cruising modes within 0.185 - 0.195 kg / hp.h. The work was carried out within the framework of the design of the aircraft "85", the topic determined at that time for the MAP as the most important.

The M-253K project was based on the following principles:
— minimal changes in the M-251TK design, which was justified by the high accuracy and reliability of the M-251TK components and assemblies, confirmed during tests, as well as the short time allotted for development;
– maximum use of energy exhaust gases in order to minimize the boost of the main piston engine in terms of boost and obtain the specified fuel consumption (the increase in boost, in comparison with the M-251TK, was carried out in take-off mode by only 7%).

M-253K was supposed to be a combined installation, consisting of two power units, an engine with three impulse turbines and a turbocharger with a variable jet nozzle, which received energy from the exhaust gases of the engine. The use of impulse turbines made it possible to improve efficiency by 10-11%, the use of a powerful turbocharger with an altitude of 11,000 m, with high efficiency in all modes, using the reaction of exhaust gases in an adjustable jet nozzle, made it possible to increase operational efficiency by 20-25%.

In September 1949, a working draft was completed and drawings of new units were developed - impulse turbines and a TK-36 turbocharger. In the course of the design, the compression work in the monitoring station was reduced, and the injection of a water-to-alcohol mixture was used for forced modes. As a result of the work carried out, OKB-36 managed to obtain an effective and completely reliable unit, the basis of which was the spent piston engine. His rational scheme, in the form of a four-row six-block star with liquid cooled, made it possible to create a compact and rigid design, which provided a low specific gravity and high performance data.
In the same September 1949, Decree No. 3929-1608 for the 85 aircraft put forward the following basic requirements for the M-253K engine:
- takeoff power - 4300 hp;
- rated power at an altitude of 8000-9000 m - 3200 hp;
— specific consumption fuel in the mode of 0.5-0.6 rated power - 0.185-0.195 kg / hp h;
- dry weight (without pressurization unit) - 1900 kg.

In December 1950, it was necessary to submit the engine to the State 100-hour bench tests. For bench and flight tests, it was necessary to build 20 copies of the M-253K in a short time.

In January 1950, the first engine was ready, then 23 more engines were built. In June-December, 100-hour factory tests are carried out on several engines. In December 1950, the M-253K, together with the TK-36, was presented for State bench tests, which it completed with positive results in early February 1951, confirming the full compliance of all parameters with the given ones, as well as the reliability of the design. At the end of the State Tests, the M-253K receives the designation VD-4K.

VD-4K engine.

In the second half of 1950, the VD-4K was installed on the Tu-4LL flying laboratory. By the end of 1950, the first stage of flight tests was completed. One experienced VD-4K was tested, the other three were full-time ASh-73TK. These works were carried out by the LII and their positive results became a good reason for installing these engines on the first 85 aircraft. Competitors from OKB-19, with their more powerful, but more "raw" ASh-2K, did not have time for the first flight. Further tests and refinements of the VD-4K were carried out during the implementation of the joint test program on the 85 aircraft, as well as the parallel test flights of the Tu-4LL with the VD-4K. The laboratory tested all measures to refine the engine. This contributed to the acceleration of the process of joint testing. In particular, an additional fan in the engine cooling system was worked out on the Tu-4LL.

The VD-4K was finally assigned to the aircraft "85" at the end of May 1951, when it was decided to raise the "85" on the first flight with the VD-4K, since the ASh-2K was still suffering from "childhood illnesses". In the course of fine-tuning the Tu-85 engine installation, a fan was installed on the VD-4K forced cooling. Power was transmitted using a single-shaft planetary gearbox with an integrated engine ventilation system to the propeller, a five-blade AB-55 or a four-blade AB-44.

With the official completion of the Tu-85 creation program, work on the VD-4K was gradually curtailed. The creation and flight tests of the VD-4K became the pinnacle of the development of piston aircraft engine building. This required solving a wide range of problems in the field of strength and dynamics of machines, heat engineering, gas dynamics, materials science and production technology.

For the creation of VD-4K, a group of workers from OKB-36 and TsIAM was awarded the Stalin Prize in 1951.

Cylinder diameter, mm: 148
Piston stroke, mm: 144 mm
Number of cylinders: 24
Dry weight, kg: 2065 (without turbocharger)
Volume, l: 59.43
Power, hp: 3250/4300
Compression ratio: 7.0
Compressor: single stage single speed ARC
Cooling system: liquid cooling.

List of sources:
V.R. Kotelnikov. Domestic aviation piston engines.
V. Rigmant. The last piston bombers.
TsAGI. Aircraft building in the USSR 1917-1945. Book II.

Valve motor (VD)

One of the most promising and versatile types of electric drives with synchronous machines is a brushless or contactless valve motor, in which the speed and torque are controlled by the input voltage, excitation current and the advance angle of switching on the valves with self-control by the supply frequency. It has the adjusting qualities of machines direct current and system reliability alternating current.

The reliability of a conventional SM is higher than the reliability of any other machine, and in terms of cost it is second only to an asynchronous squirrel-cage rotor. Contactless SM is provided both in the usual way (using brushless excitation systems with rotating rectifiers) and new ones (using permanent magnets on the rotor, claw-shaped rotor and excitation winding on the stator, etc.).

Because of the simplicity most widespread got DC (a) and AC (b) DC motors with converters operating in the current source mode.

In contrast to a frequency-controlled drive, in a brushless motor, thyristor switching is carried out due to the EMF of the motor (machine). Machine switching eliminates high-voltage bulky reactive elements in the inverter. This greatly simplifies the circuit and reduces its overall power, and ultimately improves the quality of energy conversion. But at start-up and low speeds, switching failure occurs due to the absence or small value of EMF. In a brushless DC motor, the following starting methods are possible:

· asynchronous;

With artificial switching;

with forced switching.

The first method, with its apparent simplicity, has serious drawbacks - the start is uncontrolled and switching is necessary in power, as a rule, high-voltage circuits.

The second starting method involves the use of an autonomous inverter, which uses the reactive energy of switching elements (capacitors and chokes). In this case, the circuit becomes noticeably more complicated, the weight and cost of the inverter increase.

The third way of starting with forced switching is carried out by cutting off the control pulses or cyclically transferring the rectifier to the inverter mode for the time of switching the inverter thyristors. This method requires minimal effort. Characteristic disadvantages are a decrease in the starting torque of the engine and a slight increase in the consumed reactive power.

Forced commutation start is also carried out in an uncontrolled rectifier circuit. In this case, the inverter performs pulse-width voltage regulation. This method requires the use of transistors or gated thyristors in the inverter.

The starting problem is most simply solved in a system with a cycloconverter (b), in which the functions of rectification and inversion are performed by the same thyristors, which achieves the conversion of the voltage and frequency of the source directly into the voltage and frequency of the motor. Such a system contains a larger number of thyristors than a converter with a DC link, but due to the absence of starting devices, a single energy conversion and a decrease in the thermal current of the thyristor, it is economical and reliable.

In a circuit with a cycloconverter, natural switching is carried out over the entire speed range of the HP operation both between thyristors in working groups and between thyristors of unipolar groups. The latter occurs when the signals for switching the phases of the network and the motor coincide in time. Machine switching is performed by the motor EMF between thyristors of unipolar groups at frequencies above 0.1 ... 0.15 of the motor speed.

HP reversal is simple and possible in two ways:

· advance angle increase more than 90 0 ;

· reversal of two phases of signals with DPR.

The bandwidth of the HP switch is regulated by changing the lead angle b 0 or b (the angles between the current and, accordingly, the no-load EMF and the machine voltage). There are the following ways to control the VD switch:

b 0 \u003d b 0 min \u003d f(g, q) for d=d min =const;

b=bmin= f(g) when d=dmin=const,

where b 0 \u003d b + q; q is the load angle of the synchronous machine; b=g+d; g - switching angle (takes into account switching phase overlap); d - margin angle (takes into account the error of the control system and the recovery time of the blocking properties of the thyristors).

With the control mode b=const, the lead angle remains constant in all drive modes and is calculated according to the maximum load value. In this case, the no-load current corresponds to the largest value of the margin angle (40 ... 50 °), although it is enough to have 3 ... 5 ° to restore the locking properties of thyristors.

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Content
Introduction
1 . Current state issue in the area VD design
2 . Overview of HP designs, design selection and description

2.1 Switched reluctance motor
2.2 Excited synchronous machines from permanent magnets
2.3 Choice of HP design

3 . Analytical calculation of the magnetic system of a permanent magnet motor

3.1 Calculation of the rotor
3.2 Stator calculation
3.3 Trapezoidal calculation th groove

Introduction

At present, most developed countries are widely introducing high-tech electrical products, which not only solves the issues of reducing energy consumption, but also allows you to create electrical complexes with low losses and a number of new qualities. Advances in the field of power and microprocessor technology have opened up favorable conditions for creating a new generation of electric drives based on brushless electric motors (RM). Almost all the leading electrical engineering firms in the world are currently mastering the production of such electric motors.

Leading electrical companies have mastered the production of permanent magnet motors (from a few watts to hundreds of kilowatts) for various fields, including aerospace, transport, medical, machine tool, computer technology, etc.

One of the main obstacles to the widespread introduction of valve drives in equipment is the high cost of permanent magnets. Therefore, the main application of VDs was found in the aviation and space industry, where the cost of the product is a secondary parameter.

The project developed the terms of reference for the design of a brushless motor, considered methods for analyzing electromagnetic and electromechanical processes in the HP, made an analytical calculation of the magnetic system of a brushless motor and built computer model magnetic system.

1. The current state of the issue in the field of designing VD

The main directions for improving the VD are: the development and use of more advanced magnetic materials, the development of new EMF design options, the miniaturization of the electronic part of the machine, and the creation of new types of sensors. Over the past 10-15 years, in our country and abroad, technologies have been developed and the production of high-coercivity hard magnetic materials based on intermetallic compounds of cobalt with rare earth metals has been launched. The high specific energy of rare-earth permanent magnets can significantly reduce the weight and overall dimensions of electrical machines. The improvement of circuits, designs and manufacturing technology of PCs is currently taking place through the widespread use of hybrid thin-film technology for the production of large integrated circuits and power large integrated circuits (VLSI), the complexity of manufacturing of which is weakly dependent on their structural complexity. Fundamentally new functional and circuitry possibilities for integrating digital and analog data processing, filtering and signal conversion are opened up, the most important of which is the creation of fault-tolerant powerful integrated distributed structures, “self-protected” from overloads, load and power disturbances, and preserving system characteristics in case of local failures in the structure itself. VLSI structures make it possible to almost deterministically set almost any resource of the electronic part of the VD. Along with the improvement of materials, elements, structures, production technology and specifications ever more stringent requirements are imposed on the reliability of the VD. These requirements are most clearly manifested in the development and creation of actuating elements of adjustable electric drives of special mechanisms and automation systems. aircraft, when, depending on the purpose of the engine and the conditions of its use, reliability is determined by a combination of several properties: non-failure operation, durability and persistence. The requirements for ensuring high probability are most often put forward as reliability indicators. uptime(p = 0.99500 ... 0.99999), time to failure (5000 ... 20000 h), assigned resource (110000 ... 350000 inclusions) with a total operating time of 250 ... 5500 h) or assigned service life (14 ... 20 years), average shelf life (9 ... 20 years). In this regard, already at the stage of design study of HP options, it is necessary to take into account the current level of development of electrical engineering and electronics technology, analyze possible failures of elements and investigate their effect on the output characteristics and engine performance, provide for optimal backup methods, measures for diagnosing the technical condition and VD reliability management. These issues are components of a systematic approach to the design of complex technical systems. One of the ways to create high reliability motors is to increase the number of EMF phases at a constant motor power. This makes it possible to reduce the amount of current in each phase of the open winding and to make the PC in an integrated design, which makes it possible to embed the latter inside the body of the electric machine. The resulting variety of possible connection schemes, power supply methods and algorithms for switching phases of the armature winding makes it possible to implement EMF, the structure and parameters of which can automatically change depending on the goals and operating conditions, and the autonomous execution of switching channels for each phase will provide increased reliability of the machine based on the principles of functional reservations.

If in a machine with a small number of phases, the vast majority of element failures lead to complete failure motor, then in a polyphase machine, operability can be maintained, although the output characteristics of the motor change. This gives rise to the possibility of another way of redundancy. Increasing the number of EMI phases reduces the influence of a failure in the control channel or an EMI phase on the characteristics of the VD. On the other hand, an increase in the number of phases leads to an increase in the probability of failure in one of them. Therefore, it is necessary to look for a reasonable compromise here, based on the requirements for output characteristics, on the one hand, and the resource and reliability of the machine, on the other hand. With a known probability of failure of one channel, it is possible to find such a number of EMF phases that provide the specified indicators of engine reliability, taking into account the possibility of one or more failures in the control equipment and satisfactory output characteristics of the HP. The use of this method of redundancy has its own characteristics, which must be taken into account in the study physical processes and design of the VD in general. The method coincides with the general desire to increase the number of EMF phases, based on the conditions for improving performance. To solve these problems, it is necessary to develop general methods for studying electromagnetic processes in order to obtain a quantitative assessment of the characteristics of multi-phase HP in normal operating modes and in case of failures. individual elements scheme.

2. Overview of design options for HP, selection and description of the design

As part of the VD, three types of non-contact electrical machines have found application, mainly:

1) Synchronous machines with excitation from permanent magnets.

2) Inductor machines with excitation winding (they are also called axial).

3) Synchronous reluctance machines (a valve motor based on them is also called a valve reluctance motor, which confuses the terminology of the names of HP based on machines 2 and 3).

In principle, it is possible to use a classical synchronous machine with electromagnetic excitation and even an asynchronous machine. But in the first case, one of the main advantages of the VD is lost - non-contact, and in the other case - it is difficult to implement feedback on the position of the rotor.

2.1 Switched reluctance motor

Switched reluctance motor (VID) is relatively new type electromechanical energy converter, which combines the properties of both an electric machine and an integrated system of a controlled electric drive. Like any electric motor, it provides the conversion of electrical energy that comes from the supply network into mechanical energy transmitted to the load. As a controlled electric drive system, VID makes it possible to control this process in accordance with the characteristics of a particular load: adjust the speed, torque, power, and so on.

VID is a fairly complex electromechatronic system, the block diagram of which is shown in fig. 2.1

Figure 2.1 - Block diagram VIEW

It consists of: an inductor machine (IM), a frequency converter, a control system and a rotor position sensor (RPS). The functional purpose of these VID elements is obvious: the frequency converter provides power to the phases of the IM with unipolar voltage pulses rectangular shape; The IM performs electromechanical energy conversion, the control system, in accordance with the algorithm embedded in it and the feedback signals coming from the rotor position sensor, controls this process.

In its structure, VIE is no different from classical system adjustable electric drive. That is why it has all its properties. However, unlike a controlled electric drive, for example, with an asynchronous motor, IM in VID is not self-sufficient. It is fundamentally unable to work without a frequency converter and control system. The frequency converter and the control system are integral parts of the IM, necessary for the implementation of electromechanical energy conversion. This gives the right to assert that the totality of the structural elements presented in Fig. 1 is not only a controlled electric drive system, but also an electromechanical energy converter.

IM, which is part of the VID, can have various designs. On fig. 2.2, for example, shows a cross-section of a 4-phase 8/6 configuration IM. When designating the IM configuration, the first digit indicates the number of stator poles, the second - the rotor.

Rice. 2.2 Cross section of a 4-phase 8/6 configuration IM.

Analysis of fig. 2.2 shows that IM has the following design features.

The stator and rotor cores have a salient pole structure.

The number of poles is relatively small. In this case, the number of stator poles is greater than the number of rotor poles.

The stator and rotor cores are laminated.

The stator winding is concentrated coil. It can be single or multi-phase.

The IM phase, as a rule, consists of two coils located on diametrically opposite stator poles. Known IM with a double number of stator and rotor poles. In the 4-phase version, they have a 16/12 configuration. The phase of such an IM consists of two pairs of coils, which are located on the stator poles in such a way that their axes are orthogonal.

The phase coils may be electrically connected in parallel or in series; in magnetic - according or counter.

There is no winding on the IM rotor.

VID is both an electric machine and an integrated variable drive system. It is an organic unity of IM, frequency converter and microprocessor system management. Therefore, all its advantages and disadvantages can be divided into two groups:

Characteristics due to MI;

Characteristics due to frequency converter and control system;

In accordance with these groups, the advantages and disadvantages of VID are given below.

Advantages of VID and disadvantages due to MI:

Advantages

Simplicity and manufacturability of IM design;

Low cost;

High reliability;

High maintainability;

Low losses in the rotor;

Minimal temperature effects;

Low moment of inertia;

Ability to work at high speeds;

Ability to work in aggressive environments;

High degree of recycling.

Flaws

High level of noise and vibration;

Poor use of steel;

Operation is only possible in conjunction with a frequency converter;

Significant stamping waste;

Advantages and disadvantages of VID, due to the frequency converter and control system:

Advantages

Possibility of optimal control of the process of electromechanical energy conversion for a particular load device;

High weight and size and energy characteristics.

Flaws

Reduced electrical compatibility with the network due to high content higher harmonics in winding currents.

Applications VID

It is most expedient to use VID as an electric drive for mechanisms in which, according to operating conditions, regulation is required in a wide range of rotational speeds. An example here would be the electric drives of machine tools with a numerical program management and industrial robots.

The efficiency of the use of VIM is significantly increased if the need for speed control is combined with difficult operating conditions, as is the case in electric drives for metallurgy, mining and rolling stock of electric vehicles.

The industry has big class devices and mechanisms using an unregulated electric drive, where energy efficiency increases significantly when using an adjustable electric drive. These devices primarily include compressors, pumps and fans. The use of VIEW here is very promising.

2.2 Permanent magnet synchronous machines

The valve motor is a synchronous motor based on the principle of frequency regulation with self-synchronization, the essence of which is to control the stator magnetic field vector depending on the position of the rotor. BLDC or PMSM motors are also called brushless DC motors, because the controller of such a motor is usually powered by DC voltage.

This type of motor is designed to improve the properties of DC motors. High requirements for executive mechanisms(in particular, high-speed microdrives for precise positioning) led to the use of specific DC motors: brushless three-phase motors direct current (BLDC or BLDC). Structurally, they resemble AC synchronous motors: the magnetic rotor rotates in a laminated stator with three-phase windings. But RPM is a function of load and stator voltage. This function is implemented by switching the stator windings depending on the coordinates of the rotor. BLDCs are available with separate sensors on the rotor and without separate sensors. Hall sensors are used as individual sensors. If the execution is without separate sensors, then the stator windings act as a fixing element. When the magnet rotates, the rotor induces an EMF in the stator windings, resulting in a current. When one winding is turned off, the signal that was induced in it is measured and processed. This algorithm requires a signal processor. For braking and reversing the BDPS, a power reverse bridge circuit is not needed - it is enough to apply control pulses to the stator windings in reverse order.

In a brushless motor (VD), the inductor is on the rotor (in the form of permanent magnets), the armature winding is on the stator (synchronous motor). The supply voltage of the motor windings is formed depending on the position of the rotor. If a collector was used for this purpose in DC motors, then in a brushless motor its function is performed by a semiconductor switch (rotor position sensor (RPS) with an inverter).

The main difference between a VD and a synchronous motor is its self-synchronization with the help of a DPR, as a result of which, in VD, the field rotation frequency is proportional to the rotor speed.

The stator has a traditional design and is similar to the stator asynchronous machine. It consists of a body, a core made of electrical steel and a copper winding laid in grooves along the perimeter of the core. The number of windings determines the number of motor phases. For self-starting and rotation, two phases are sufficient - sine and cosine. Usually VD three-phase, less often - four-phase.

According to the method of laying turns in the stator windings, motors with reverse electromotive force trapezoidal (BLDC) and sinusoidal (PMSM) waveforms. According to the method of supply phase electricity also varies trapezoidal or sinusoidally in the respective motor types.

The rotor is made using permanent magnets and usually has two to eight pairs of poles with alternating north and south poles.

At first, ferrite magnets were used to make the rotor. They are common and cheap, but they have the disadvantage of a low level of magnetic induction. Magnets made from alloys of rare earth elements are now gaining popularity, as they allow you to get high level magnetic induction and reduce the size of the rotor.

The rotor position sensor (RPS) provides feedback on the position of the rotor. His work may be based on different principles-- photoelectric, inductive, on the Hall effect, etc. Hall and photoelectric sensors have become the most popular, since they are practically inertialess and allow you to get rid of the delay in the feedback channel on the position of the rotor.

The sensor signals are converted by the control device into a combination of control voltages that control the power switches, so that two switches are turned on in each cycle (phase) of the engine operation and two of the three armature windings are connected in series to the network. Armature windings U, V, W are located on the stator with a shift of 120 ° and their beginnings and ends are connected so that when switching the keys, a rotating magnetic field is created.

The control system contains power switches, often thyristors or insulated gate power transistors. Of these, a voltage inverter or a current inverter is assembled. The key management system is usually implemented using a microcontroller. The presence of a microcontroller requires a large number of computational operations for engine control.

The principle of HP operation is based on the fact that the HP controller switches the stator windings so that the stator magnetic field vector is always orthogonal to the rotor magnetic field vector. Using pulse-width modulation (PWM), the controller controls the current flowing through the HP windings, i.e. the vector of the magnetic field of the stator, and thus the moment acting on the HP rotor is regulated. The sign of the angle between the vectors determines the direction of the moment acting on the rotor.

Degrees in the calculation - electrical. They are less than geometric degrees in the number of rotor pole pairs. For example, in a HP with a rotor having 3 pairs of poles, the optimal angle between the vectors will be 90° / 3 = 30°

Switching is performed in such a way that the rotor excitation flux -- Ф 0 is maintained constant relative to the armature flux. As a result of the interaction of the armature flux and excitation, a torque M is created, which tends to turn the rotor so that the armature and excitation fluxes coincide, but when the rotor turns under the action of the DPR, the windings switch and the armature flux turns to the next step.

In this case, the resulting current vector will be shifted and stationary relative to the rotor flux, which creates a moment on the motor shaft.

In the motor mode of operation, the stator MMF is ahead of the rotor MMF by an angle of 90°, which is maintained with the help of the DPR. In the braking mode, the stator MMF lags behind the rotor MMF, the angle of 90° is also maintained using the DPR.

The engine is controlled by the HP controller. The HP controller regulates the torque acting on the rotor by changing the PWM value.

Unlike a brushed DC motor, switching in the HP is carried out and controlled electronically.

Control systems that implement algorithms for pulse-width regulation and pulse-width modulation in the control of the HP are widespread.

The system that provides the widest range of speed control is for motors with vector control. With the help of a frequency converter, the motor speed is controlled and the flux linkage in the machine is maintained at a given level.

A feature of the regulation of an electric drive with vector control is that controlled coordinates measured in a fixed coordinate system are converted to a rotating system, a constant value is allocated from them, proportional to the components of the vectors of controlled parameters, according to which control actions are formed, then the reverse transition.

The disadvantage of these systems is the complexity of the control and functional devices for a wide range of speed control.

Advantages and disadvantages of VD

In recent times, this type of engine is rapidly gaining popularity, penetrating many industries. It finds application in various fields of use: from household appliances to rail transport.

ID with electronic systems controls are often combined best qualities contactless motors and DC motors.

Advantages:

High speed and dynamics, positioning accuracy

Wide speed range

Non-contact and maintenance-free -- brushless machine

Can be used in explosive and aggressive environments

Large torque capacity

High energy performance (efficiency over 90% and cos over 0.95)

Long service life high reliability And increased resource operation due to the absence of sliding electrical contacts

Low overheating of the electric motor, when operating in modes with possible overloads

Flaws:

Relatively complex engine management system

The high cost of the motor, due to the use of expensive permanent magnets in the design of the rotor

2.3 Choice of HP design

In this course project, the task is to analytically calculate a brushless motor with a power of 11 watts and a rotation speed of 15,000 rpm and subsequent computer simulation of the magnetic system in the Elcut program for subsequent optimization of the magnetic system. Based on the required output parameters, it would be advisable to choose a permanent magnet reluctance motor. The stator has a traditional design in the grooves of which a three-phase winding is laid. The rotor is made using permanent magnets of the KS37A-130 brand and has four poles with a bandage made of titanium fig. 2.3.

Figure 2.3 - HP rotor design

3. Analytical calculation of the magnetic system of a brushless electric motor

3.1 Rotor calculation

Current frequency in the stator winding, Hz,

(4.1)

Power factor,

Coefficient,

determined by dependency

Rated power, VA,

(4.2)

The volume of the magnet

(4.3)

valve motor electromagnetic rotor

where is the magnet utilization factor;

KS25DS-240 magnet is used as rotor magnets.

Outer diameter of rotor magnets, m

(4.4)

where is the length of the magnet, m;

magnet height (set), m;

The minimum outer diameter of the rotor magnets, m,

(4.5)

where is the thickness of the spacer between the magnets, m;

We accept for technological reasons.

Pole arc of the magnet, m,

(4.6)

Magnet pole width, m,

(4.7)

Power line of the magnet, m,

(4.8)

Power line of the rotor yoke, m,

(4.9)

where is the shaft diameter (set and specified after mechanical calculation), m;

3.2 Stator calculation

Stator inner diameter, m,

(4.10)

Pole division of the stator, m,

(4.11)

Pole overlap ratio,

(4.12)

Estimated pole overlap ratio,

(4.13)

(4.14)

where is the number of slots per pole and phase (set);

Tooth division of the stator, m,

(4.15)

Winding pitch along the grooves,

(4.16)

Winding shortening factor,

(4.17)

Distribution coefficient,

(4.18)

where, if it is a fraction, the numerator of the improper fraction is taken;

Figure 6.1 - Stator winding diagram

bevel ratio,

(4.19)

where is the bevel in slot divisions (specified);

winding ratio,

(4.20)

Estimated phase voltage, V,

(4.21)

where is the mains voltage, taking into account the voltage drop across the transistors

inverter, in connecting wires;

Estimated phase EMF, V,

(4.22)

Magnetic flux, Wb,

(4.23)

The number of turns in a phase,

(4.24)

where is the field shape factor;

(4.25)

where is the number of parallel branches of the stator winding;

Let's use a two-layer winding.

The number of turns in the section,

(4.26)

We accept the number of turns in the section

We specify the number of turns in the phase,

(4.27)

We specify the value of the flow, Wb,

(4.28)

(4.29)

Estimated current of the stator phase, A,

(4.30)

Cross section of the effective conductor,

(4.31)

where is the current density (given);

Cross section of an elementary conductor,

(4.32)

where is the number of parallel conductors in the groove;

Bare wire diameter, mm,

(4.33)

According to the directory, select the wire,

The final current density

(4.34)

The area occupied by insulated conductors in the groove,

(4.35)

Linear load, A/m,

(4.36)

Stator yoke height, m,

(4.37)

where is the magnetic induction in the stator yoke, T;

the filling factor of the package with steel, is determined by the brand and

coated steel;

length of the stator package, m;

3.3 Trapezoidal slot calculation

Tooth width, m,

(4.38)

where is the length of the air gap, m;

magnetic induction in the teeth, T;

Groove slot width, mm,

(4.39)

the height of the wedge is assumed to be 0.00035-0.0035, m;

h p - the height of the groove is given, m;

The area of the groove, we determine using the calculation in the Compass S p \u003d 0.000102m 2.

Figure 4.2 - Sketch of the stator slot

Groove fill factor,

(4.40)

The fill factor is within the required range of 0.30 - 0.48.

Outer diameter of the stator, m,

(4.41)

5Investigation of the VD magnetic system based on a field computer model

To study the VD magnetic system based on the field model and ANSYS software was used.

As the initial data for the calculation, we took the results of the analytical calculation of paragraph 4 of this work.

In ANSYS, a hermetic model was formed according to the classical equivalent circuits, Figure 5.1.

Figure 5.1 - Geometric model

As a result of the analytical calculation in ANSYS, the following characteristics were obtained

Figure 5.2 - Performance data

Next, the calculation of the electromagnetic field was carried out on the basis of the field model. As a result, the following were obtained: the distribution of magnetic induction, the distribution of magnetic flux, the distribution of magnetic and ohmic losses in the active part of the electric machine.

Figure 5.3 - Distribution of induction in the active part of the electric machine

Figure 5.4 - Distribution of the magnetic flux in the active part of the electric machine

Figure 5.5 - Distribution of magnetic losses

Figure 5.5 - Distribution of ohmic losses (losses in copper)

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