DEVELOPMENT OF MOTOR-GENERATOR FOR A HIGH-EFFECTIVE FLYWHEEL ENERGY STORAGE SYSTEM
A.Mosiundz, stud.
KremenchukMykhailoOstrohradskyiNationalUniversity
Pershotravneva st., 20, 39600, Kremenchuk, Ukraine, e-mail:
Introduction. Flywheelisadeviceforstoringkineticenergyduetorotationalmotiontothefollowingreturnittoperformusefulwork.Thispaperproposestouseflywheelcombined withelectricmachine (EM) in energystoragesystem.Such system should be considered as an electromechanical energy device (EMED).
Thistypeofstoragedeviceshasmanyadvantages, suchas: thehighestspecificenergycapacity (alongwithchemical),theabilitytostoreenergywith usingrelativelylow-powersourcesifthechargestoragetimefarexceedsthedischarge ,ahighefficiency and high reliability, wide range of applications.
Since the design and dimensions of flywheels is not uniform, then for each type of performance it have to be designed its driving electric machine. Accordingly, the paper presents an example of development EM for the selected design of flywheel energy storage system.
Objective.Optimal construct of the system and its components, development and designing of a driving EM.
Material and research results. The most important requirements for electrical machines, which are used in flywheel energy storage systems, are no sliding contact and ability to work on extra high speed with high efficiency. These requirements are put forward to achieve maximum efficiency of the system.From the existing types of electric machines a brushless DC motor (BLDC) mostly matches such requirements. These contactless machines have a fairly simple electric circuit, do not consume field energy and have a high efficiency, very high reliability. Thereby BLDC was chosen as the driving motor-generator for this system.
In order to determine the initial parameters of BLDC, it is recommended to choose the optimum design of energy storage system: colonic flywheel in vacuum coat,mounted on magnetic bearings. The design of flywheel allows us to put BLDC inside it, while the motor have the inner fixed stator and outside rotor.
To determine the geometry of the stator and rotor of the motor-generator it is necessary to define the size of the flywheel. Basing on existing projects [1, 2] were selected following parameters of the flywheel: the outer radius of the rim m, the inner radius of the rim (outer radius of the rotor) m. Assume the mass of the flywheel , then its height is
m,(1)
whereisdensity of carbon fiber flywheel is wounded with.
Then length of BLDC, based on its design, should not exceed
m,(2)
wheremisdisc width of the flywheel.
Moment of inertia can be represented as
.(3)
The maximum energy that can be accumulated in 1 kg of flywheel’s rim made of carbon fiber (with tensile strength MPa) is 3,7 GJ (1 ). Expression for the energy has the following form
.(4)
Then, from (4) we found the speed rpm on the outer surface of the flywheel. This is the maximum speed with no risk of destroying the fibers. Such speed must be provided by BLDC.
Simulation of motor-generator implemented in the Ansoft Maxwell software, as this program accelerates processes of designing and optimization the electrical machines, makes it possible to analyze many options in minutes and get required characteristics, allows us to create 2D and 3D models of the machines for a more accurate calculation with finite element method.
Parameters that are not among the initial data are constructively recommended, selected from [3-6] and adjusted during operating with the simulation.
When the parameters of BLDC, the geometry of the stator and rotor, configuration of the winding and poles are specified to Ansoft Maxwell RMxprt, the model is created. By using software analysis functions there were received properties of the designed motor that shown in Fig. 1.
a)b)
Figure1 – Properties of the designed BLDC:
a) efficiency; b) speed-torque characteristic
Fig. 1 shows that the efficiency of the designed motoris 96-98% at operating speed.
Maxwell 2D allows to create automatically geometry of the machine, to set properties of materials, configurations of windings and magnetization of permanent magnets according to preliminary data.
At the next step itis needed to specify such requiredparameters for future modeling of the machine components as: configuration of steel and conductivity of materials.
The program calculates winding resistance and its additional inductance. In this case, the winding resistance specified infinitely large to consider BLDC in idle mode.
At the end of the program analysis and calculation data there were obtained 2D model of the motor with the picture of the magnetic flux distribution (Fig. 2).
Figure2 – Magnetic flux distribution
Conclusions. During the research it was justified using BLDC as a drive machine for a flywheel energy storage system because only that type of electric machine has all needed features and characteristics. High efficiency is required because a drive motor efficiency directly affects the entire energy system efficiency, which is one of the most important parameter of any energy storage system.
Accordingly to the structure of the chosen system and the requirements for its operation, it was designed BLDC with using Ansoft Maxwell software,set matching the characteristics of the machine with the requirements of energy storage system from the obtained graphs.
REFERENCES
1.Technology. Aboutflywheelenergystorage [Electronic recource]. – Access mode:
2.Vycon's regen clean energy storage flywheels improve rail energy efficiency and reduce operational costs [Electronic recource]. – Access mode:
3.TulupovP. V. BrushlessDCmotor: extended abstract of PhD dissertation: 05.09.01 “Electromechanics and electric devices”. – Samara, 2001.(inRussian)
4.BalagurovV. A., GatleevF. F. Electric generators with permanent magnets. – Moscow: Energoatomizdat, 1988. – 280 p. (in Russian)
5.MaslennikovV. S. Designing BL motors according to the dimensional criteria// Electrical engineering. – 1996. – № 6. – pp. 19-22.(inRussian)
6.MorozovskyiM. J., KhotomlenskyiJ. A. Selecting the optimum thickness of the rotor poles in the BLDCs // Electricalengineering. – 1992. - № 1. – pp. 11-14. (in Russian)
А.А. МосюндзРозробка мотор-генератора для високоефективноїсистеми накопичення енергії на базі супермаховика
Електромеханічні та енергетичні системи, методи моделювання та оптимізації. Збірник наукових праць XІI Міжнародної науково-технічної конференції молодих учених і спеціалістів у місті Кременчук 10–11 квітня 2014. – Кременчук: КрНУ, 2014. – С. ХХ–ХХ.
У роботі було обрано оптимальну конструкцію системи накопичення енергії на базі супермаховика і, відповідно до неї, обґрунтовано використання вентильного двигуна з постійними магнітами у якості приводного мотор-генератора. Виконано моделювання даної електричної машини у програмному пакеті AnsoftMaxwell, отримано характеристики спроектованого двигуна та визначено їх відповідність вимогам системи. / A. Mosiundz
Development of motor-generator for a high-effective flywheel energy storage system
Electromechanical and energy systems, modelling and optimization methods. Proceedings of the 12th International conference of students and young researchers in Kremenchuk april 10–11, 2014. – Kremenchuk: КrNU, 2014. – PP. ХХ–ХХ.
This paper contains selection optimum design of flywheel energy storage system, and according to it, justified using brushless DC motor as a drive machine. The model of this electric machine was developed in Ansoft Maxwell software, characteristics of the machine were received and defined their compliance with the requirements of the system.