Super-High-Speed Electric Machines with Magnetic Rotors
Development of Scientific Basis for Creating a New Generation of Super-High-Speed Electric Machines with Magnetic Rotors
Tech Area / Field
- MAN-MCH/Machinery and Tools/Manufacturing Technology
3 Approved without Funding
Russian Academy of Sciences / Institute of Metals Superplasticity Problems, Russia, Bashkiria, Ufa
- TsKBM, Russia, St Petersburg\nMGTU (Moscow State Technical University), Russia, Moscow
- DARIM Control Technologies, Korea, Taejon
Project summaryThe State of the Art in the Field and the Impact of the Proposed Project on the Progress in the Field.
Application of high speed microturbogenerators, microturbocompressors, high speed turbo-molecular pumps, inertial energy-storage devices, technological and medical centrifuges, high speed electric spindle refers to ecologically safety efficient technologies providing a decrease in power and material expenditures, an increase in quality of civil market production.
At present its is evident that magnetoelectric energy converters are characterized by the highest efficiency, widest range of control and highest accuracy. The following two mutually substituting groups of magnets being most advance in their technical characteristics are widely used in electric motors and generators. One group is based on rare earth elements and the one is based on chromium-cobalt system alloys.
By present there have been performed bulk studies of rare earth element base alloys for their application in high speed electric machines. As for studies of chromium-cobalt system alloys aimed at promoting their wide practical application, they are only in the initial stage. This system alloys can be successfully used in high speed electric machines as being more strength and technological and less expensive. Compared to rare-earth magnets these alloys possess a relatively less coercive force that makes it possible to perform their magnetization and demagnetization fitting the required level as a component of an electric machine. This seems very useful for production and exploitation.
The first and basic problem is connected with material science and a technology for producing billets of magnets.
The chromium-cobalt system alloys cast and heat treated according to the traditional technique have a number of magnetic characteristics important for their practical application. However, they are not ductile and have relatively non-uniform structures. This hinters their application in high speed electric machines. For overcoming these drawbacks it is necessary to correct chemical compositions of these alloys, develop and coordinate special regimes of casting, thermo-mechanical and thermo-magnetic processing of billets.
In terms of strength of articles it is necessary to provide continuity, uniformity and ductility of billets. For this it is required to optimize casting of magnetic alloy billets of required dimensions and guaranteed quality, control mechanical properties and in case of necessity to form a rotor from several magnetic billets by solid state joint since any other structural decisions are not suitable in view of dynamic stability of a high speed rotor. Concurrently, it is necessary to preserve magnetic and strength properties of the given group alloys. For real implementation of the given technology a powerful automated plant for thermomagnetic processing of large bulks of rotors is required
The second problem is a design technological problem relating to creation of high speed machines by using chromium-cobalt system alloys.
With reference to the rotor the tasks relating to stable joint of chromium-cobalt magnets with rotor structural components are to be solved, for example, methods of soldering (brazing), welding, etc. It is promising to create cylindrical and disc type composite rotors produced by methods of strain thermo-mechanical processing of billets. A plant for magnetic testing (controlling) billets and rotors as a whole is required.
As for the stator its working surface should be performed so that to reduce power losses in a chromium-cobalt magnet (resulted) from higher harmonics of the magnetic field. It is necessary to analyze principles of magnetization and demagnetization of magnetic rotors by a winding of a stator and this circumstance should be taken into account while designing a stator. It is essential to create principles for designing high speed machines with relatively weak and partially magnetized magnets with pulse regimes of magnetization, stabilization and demagnetization. Particular software for analyzing similar machines is required.
The application of chromium-cobalt system magnets with uniform microstructure and high ductile characteristics provides creating electric machines with power above 100 kV and frequency of rotation (60…70)103 rev/min. There are no appropriate means of electromechanical testing for such powerful high speed electric machines. Thus, it is essential to create special plants for considering the distribution of power losses in a machine, and particular in a rotor, measuring statistic and dynamic characteristics of current and moment, as well as conditions for preserving rotor magnetization and its demagnetization in the process of retardation of its rotation.
The third problem is a problem connected with design and technological strength of a rotor as a whole.
It is essential to create a methodology for evaluating long-term strength of rotors in combination with centrifugal, bending and temperature-strain stresses.
The long-term strength of rotors mainly depends on thermo-cycling of a structure which accompanies each start and stop of a high speed electric machine. The fact that rather small-scale high speed electric machines possess high power causes additional difficulties connected with removal of relatively large power losses from the machine interior.
It is advisable to design and create a required complex of equipment for testing strength of rotors prior to their assembly into an electric machine. Creation the facility for testing of rotor strength to rupture via its high speed rotation is of special urgency.
Fields of application of developing high speed electric machines with chromium-cobalt system alloys are the following:
– turbo-generators and turbo-compressors;
– turbo-molecular pumps;
– inertial energy-storage devices;
– technological and medical centrifuges;
– electric spindles and electric drivers.
The range of power is from tens of Watts to hundreds of kiloWatts.
The authors of the present proposal think, that in case of solution of the tasks set, the electric motors using chromium-cobalt magnets together with integral electron moduli can successfully be used in domestic high speed electric drives.
While studying the status of the above mentioned problems the authors of the present proposal have conducted a number of preliminary joint investigations and made the following conclusions:
– it is essential to develop a complex character of investigations by material scientists, technologists, designers and electromechanical engineers;
– it is advisable that the Institute for Metals Superplasticity Problems(IMSP) should take preferential participation in solution of the first problem, the Bauman Moscow State Technical University (BMSTU) – in the solution of the second problem and Central Design Bureau on Machine-building (CDBM)– in solution of the third problem.
The scientific basis and experience of IMSP – new developments in the field of plasticity and superplasticity of metals, experience in structural control of properties of structural materials, preliminary investigations of possibilities for improving chromium-cobalt system alloys and technological processes for producing billets out of them.
The scientific basis of experience of the BMSTU – knowledge of electromechanical converters with permanent magnets, experience in the field of using high speed drives, research and technical works on pulse magnetization of rotors out of chromium-cobalt system alloys, having any frequency of rotation.
The scientific basis and experience of CDBM – knowledge of technological bases of mass and serial production of high speed motors, commercial experience in creation of facilities for strength testing of high speed electric machines.
The Project is very promising in the terms of commercial application since its results can be successfully implemented in different branches of industry in the development of novel advanced technologies that will stimulate transition of weapon technologies to new technologies of civil products operating during long periods of time under conditions of high pressures, corrosive medium that are used in chemical industry (fabrication of thin fibres, separation of mixture components) and vacuum equipment.
The objective of this Project: solution of a large-scale complex scientific and technical problem relating to creation of high strength magnets, rotor’s and stator’s design for high speed electric machines and appropriate technological techniques, in total, providing beneficial technical and economic characteristics of novel electrotechnical products conforming to enhanced ecological requirements in the field of power-resource savings and environment protection.
The final results of the present Project will be creation of bases of a technology for producing structures of ultimately used electromechanical power converters on the basis of chromium-cobalt magnets for high speed rotor and centrifuge systems (drives, generators) meant for various technological processes. In the framework of the present proposal it is planned to perform PCT patenting of developed and optimized elements of the above technology in advanced develop countries.
The development will provide solving a number of aspects of the existing ecological problems such as:
– implementation of new ecologically pure technologies in compressor building;
– decrease in power consumption;
– decrease in specific metal content of articles;
– increase in service life of equipment.
A Plan of commercial implementation of technologies and technical decisions will be worked out which assumes consideration of possibilities for applying and identifying the results expected.
The final result of the given Project will be creation of the basic technology for producing high speed electric machines. The Project possesses large commercial potentiality since its results can be spread to other branches of industry that stimulates the transition from technologies of weapon application to development of novel technologies for articles of common use.
Expected Results and their Application.
The Project realisation will allow to attain the following main results.
– Methods for increasing service and technological homogeneity and ductility of chromium-cobalt alloys via improving a process of casting and thermo-mechanical processing.
– The physical model of solid state joint of geterogenious materials and its behaviour during superplastic deformation.
– The theory for controlling magnetisation of a rotor by pulse methods.
– Methods for designing high speed machines with chromium-cobalt magnets.
– Criteria of rational fields of application of high speed electric motors with chromium-cobalt materials of rotors.
– The technique of calculation (in the form of software) for typical types of electric machines with chromium-cobalt magnets.
– Magnets meant for stable long-term operation under conditions of high velocities of rotation 300…330 m/s and cyclic loads having the following characteristics:
– ultimate (maximum) strength sb = 800…1,100 MPa;
– ductility at room temperature d = 1…2%;
– coercivity Hc і 40 kA/m;
– remanence Br і 1.0 T;
– factor of hysteresis loop convexity g = 0.6ё 0.7.
– Methods for testing magnetic and mechanical properties of rotors of electric machine.
– Technological methods for creating sound joints of chromium-cobalt magnets with structural components of high speed rotors.
– Testing and technological specialised plants for manufacturing a new generation of high speed electric machines.
– equipment for thermo-mechanical processing of large-scale billets (up to 100 mm in diameter and 300 mm in length) out of chromium-cobalt alloy;
– a device for testing magnetic properties of rotors (2 pieces.);
– a device for testing strength of disc type and cylindrical rotors at overspeed tests up to 90,000 rev./min;
– Avant-garde projects of magneto-electric machines on the basis chromium-cobalt steel.
– a high speed motor with a power of 5-6 kW and frequency of rotation 80,000-90,000 rev./min;
– electric spindles with a single power up to 100 kW and frequency of rotation up to 24,000 rev./min and a multiple motor drive on their base.
The activities fulfilled will create requisites for designing and manufacture of a new generation of high speed electric machines providing realisation of quiet new technologies. These machines are as followings:
– turbo-compressors with a power up to 220 kW at frequencies of rotation 60,000-70,000 rev./min and an efficiency of the system of about 93-94% promoting decreasing a bulk of articles by 25-40 times and realizing an ecologically pure cycle of cryostatting;
– turbo-molecular pumps with a power up to 100 W at frequencies of rotation up to 100,000 rev./min, providing increasing an efficiency by several times.
Scope of activities.
The Project is scheduled to last 24 calendar months and requires 7123 person-days of former weapons specialists and materials science specialists and also by other support staff for the performance of the Project activities. Total amount of efforts of Weapon scientists – 182 person-months while the Project activities will spent 356.15 person-months.
The following activities will be performed in the course of realization of the submitted Project:
– Analysis of typical features and possibilities of a new generation of high speed electric machines, development of requirements for technological processes of producing billets and rotors as well as for basic specialized technological equipment.
– Investigation of chemical and phase compositions of chromium-cobalt alloys promoting specified magnetic and mechanical properties as well as methods for producing billets from them.
– Development of new technological routes and facilities for strain processing of chromium-cobalt alloys and hysteretic steels to increase their mechanical properties.
– Development of a technological process and equipment for thermal processing of large-scale billets (up to 100 mm in diameter) out of a chromium-cobalt alloy.
– Production of rotors by the method of solid state joint from a chromium-cobalt magnet (magnets) with structural (designing) components out of a structural alloy.
– Consideration of the possibility of producing composite rotors of high speed machines on the basis of a chromium-cobalt alloy.
– Development of methods of magnetization and demagnetization of rotors out of a chromium-cobalt alloy as an electric motor constituent in static and dynamic regimes.
– Development of a methodology for designing high speed electric machines with a chromium-cobalt rotor.
– Development of techniques for evaluating long-term strength of high speed rotors in the presence of combined centrifugal, temperature and bending stresses.
– Development of a design of an experimental model of a plant for testing strength of disc type and cylindrical rotors (up to 400 mm) in air.
– Preparation of a final reports and development of recommendations for commercial implementation of techniques and technologies developed.
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