PROCEEDINGS OF THE 51st ANNUAL INTERNATIONAL SCIENTIFIC CONFERENCE OF RIGA TECHNICAL UNIVERSITY SECTION „POWER AND ELECTRICAL ENGINEERING”, OCTOBER 2010 Electrical Machines and Apparatus / Elektrisk s Maš nas un Apar ti
Simulation of Induction Motor Characteristics Using A Circle Diagram
Alina Meishele (PhD student, Riga Technical University), Elena Ketnere (Dr.Sc.ing., Riga Technical University), Aleksandrs Mesnyayevs (PhD student, Riga Technical University).
Abstract – The circle diagram helps to identify all simplified induction motor circle diagram, as shown below electromagnetic values, which describe the machine’s operation (Figure 2). mode at different slip values and gives them a better description when machine’s operating mode is changing. The circle diagram is also of great importance for studying the case, when the parameters of the asynchronous machines operating mode are assumed to be constant values.
Keywords – Circle diagram, heavy-duty induction motor, mathematical simulation.
I. INTRODUCTION
In general, mathematical modeling opens new perspectives Fig. 2. A simplified construction of the induction motor circle diagram. for studying the electric machines. The possibility to replace real objects with the mathematical model provides great (1) advantages for the development and research of electric I I ( I ) machines. As it is known, one of the most popular forms of 1 00 2 the electric drive is the induction motor. It is related with the where simplicity of manufacturing and the highest safety of induction motor. Modern technologies drive the engineering industry for the U1 I 00 (2) increase of the produced electric machines power. During the Z1 Z m tests of a new machine, it is not always possible to load the machine according to its power. In such cases, if the I - is the ideal idle current, and does not depend on the slip appropriate technical supply is not available in order to receive 00 the necessary curves for electric motors with the power over ( s 0 ). This current is constant, since U1 const and 100 kW, it is possible to measure the efficiency, power factor f1 const . Therefore, the coordinates of the beginning are to and slip values, by using a circle diagram. be transferred to the I00 value, and, as the result, the circle For the convenient view of the circle diagram, it is diagram is acquired (Figure 3). [1]-[3] appropriate to use the equivalent circuit of the asynchronous machine (Figure 1.).
2 CZ1 C Z 2s
I1 I2 Z1
U1 Fig. 3. The circle diagram of the induction motor. Z m I00
Fig. 1. The equivalent circuit of the asynchronous machine. II.THE PROGRAM TEST Based on the acquired diagram, the program “Diagram” was According to the equivalent circuit (Figure 1), the stator created using the programming language FORTRAN. current can be determined by adding the constant idle current
I00 to the variable component - I2 . So, it is obtained a
141 PROCEEDINGS OF THE 51st ANNUAL INTERNATIONAL SCIENTIFIC CONFERENCE OF RIGA TECHNICAL UNIVERSITY SECTION „POWER AND ELECTRICAL ENGINEERING”, OCTOBER 2010 Electrical Machines and Apparatus / Elektrisk s Maš nas un Apar ti
The results of student’s practical work based on experiments For the comparative reasons, the calculation also was made were taken to prove the precision of this program. Nominal using the program “Diagram”. On the basis of the idle and parameters are given in the table 1. short circuit test results, this program calculates the TABLE I parameters, which are required for the construction of circle diagrams. The program calculates the operating and start-up THE THREE-PHASE INDUCTION MOTOR WITH A PHASE ROTOR characteristics with the assistance of a circle diagram. Nominal parameters For operating the program, it is essential to enter the Nominal voltage U N 220 V following parameters: the stator winding resistance R1 , the ambient temperature T, the synchronous rotation frequency Nominal current I N 28 A n1 , the nominal (phase) voltage U1N , the nominal current Nominal power PN 7.5 kW I N , the idle current I0 , idle losses P0 , mechanical losses Nominal speed n -1 N 945 (min ) Pmeh , the short circuit voltage U k (the voltage, under which Power factor cos 0.83 the nominal current is achieved) short-circuit losses (losses corresponding nominal current) Pk . Efficiency 0.84 The program will process them and generate a circle Stator winding resistance Rstat 0.183 diagram parameters, such as: the radius of diagram, the circle center in the complex plane, the point of synchronism, the idle Using the measurement results, the circle diagram was point, the short-circuit point, the infinite slip point. The constructed, which allowed to determine the performance program will also generate such nominal parameters as: the curves (see fig.4). power factor, supply power, useful power, efficiency, slip and torque. The program also generates the operating A characteristics and the start-up characteristics, which allow to m determine the starting current, the starting torque, the I k (s 0) maximum torque and the critical slip. After obtaining all these values, the circle diagram can be U f I (s ) I1 Pk / m p drawn. Results were used to construct operating and start-up 0 P2 M k characteristics with help of Microsoft Office Excel as shown P m P M m em on figure 6 and 7. I0 P1
the operating charakteristics
Fig. 4. The three-phase induction motor’s circle diagram. 80 60 The figure 4 shows the circle diagrams, which have been 40 created using the Microsoft Office Visio program. The operating characteristics are shown on the figure 5. 20 0 0 2 4 6 8 P2, kW
P1 I1 M cosFix50 nix50 sx1000
Fig. 6. The operating characteristics (based on the program data).
Fig. 5. The operating characteristics
142 PROCEEDINGS OF THE 51st ANNUAL INTERNATIONAL SCIENTIFIC CONFERENCE OF RIGA TECHNICAL UNIVERSITY SECTION „POWER AND ELECTRICAL ENGINEERING”, OCTOBER 2010 Electrical Machines and Apparatus / Elektrisk s Maš nas un Apar ti
The start-up characteristics the operating char. based on measurments
2500 300 2000 250 1500 M 200 1000 I 150 500 100
0 50 0 0,2 0,4 0,6 0,8 1 1,2 0 P2 slip 0 50 100 150 200 250
P1 I1 M cosFIx50 sx100 nix50 Fig. 7. The start-up characteristics (based on program data). Fig. 8. The operating characteristics based on measurements. Comparing the results, which were obtained manually, and the ones, using the program ”Diagram”, it is concluded that they partially coincide. The manually executed calculations the operating char. based on program data are not precise enough due to the human factor. Using the 300 computer program, it is possible to obtain the necessary 250 parameters and characteristics with no additional time losses, which occur while constructing the manual diagram. 200 The further program test was executed using the three-phase 150 traction motor “DTA 170 U2”. This motor is a part of the 100 asynchronous track drive for the underground car 81-760/61 50 P2 developed by the «Metrovagonmash». The motor parameters 0 are given in table 2. 0 50 100 150 200
TABLE II P1 I1 M cosFIx50 sx100 nix50 THE TRACTION MOTOR PARAMETERS Fig. 9. The Operating characteristics, based on the program “Diagram”. Stator winding resistance R1 0.0397 The ambient temperature T 20°C currents comparison Synchronous rotation frequency n1 1500 min-1 300
Nominal power PN 170 kW 250
200 Nominal (phase) voltage U1N 306.4 V 150 Nominal current I N 225 A 100
The idle current of I0 75.5 A 50
0 Idle losses P0 7.77 kW 0 20 40 60 80 100 120 140 160 180 200 P2 Mechanical losses Pmeh 0.7k W current I1 measur current I1 prog
Short circuit voltage Uk 85 V Fig.10. The comparison of current characteristics. Short circuit losses Pk 12 kW
The aim of research is to prove that it is possible to obtain torque comparison working performances for asynchronous motor with power 1200 over 100 kW using program “Diagramm”. For comparison the 1000 test results of motor “DTA 170U2” are given. 800 The results obtained by operating the program “Diagram” 600 are compared with the measurement results obtained by the 400 electrical equipment test center (shown on the figures 8, 9). 200 0 0 20 40 60 80 100 120 140 160 180 200 P2
torque M2 measur torque M2 prog
Fig. 11. The comparison of torque characteristics.
143 PROCEEDINGS OF THE 51st ANNUAL INTERNATIONAL SCIENTIFIC CONFERENCE OF RIGA TECHNICAL UNIVERSITY SECTION „POWER AND ELECTRICAL ENGINEERING”, OCTOBER 2010 Electrical Machines and Apparatus / Elektrisk s Maš nas un Apar ti
Alina R. Meishele is born in 1984 in Latvia. In power factors comparison 2008, she graduated the Riga Technical
0,95 University, obtaining the M.Sc.ing. degree. 0,9 Presently she is a PhD student. 0,85 In March 2007, she received the certificate 0,8 “AutoCAD 2007”. 0,75 0,7 0,65 0,6 0,55 0,5 0 20 40 60 80 100 120 140 160 180 200 P2 power fact. cosFI measur power factor cosFI prog Elena K. Ketnere is born in 1963 in Latvia. In 1985, she graduated the Riga Polytechnical Fig. 12. The comparison of power factor characteristics. Institute (RPI), the Faculty of Electrical and Power Engineering, obtaining the qualification of Engineer in the Electrical Machines and the Apparatus specialty. In 2002, she obtained the efficiencies comparison Dr.Sc.ing. degree.
0,95 After graduating the RPI, E. Ketnere has worked as an engineer at Riga Electric Machine- 0,9 building Plant (1985-1995). In 2005, she was appointed as the Associate Professor in the 0,85 Department of Electrical Machines and Apparatus
0,8 of the Riga Technical University, where she works up to date. 0,75 Scientific activities of E.Ketnere are related to the Mathematical Simulation of the dynamic regimes of the Electrical Machines. The results of 0,7 0 20 40 60 80 100 120 140 160 180 200 her research are reflected in more than 20 scientific publications and technical P2 reports in International Scientific conferences.
efficiency measur efficiency prog
Aleksandrs A. Mesnyayevs is born in 1985 in Fig. 13. The comparison of efficiency characteristics. Latvia. In 2008, he graduated the Riga Technical University, obtaining the M.Sc.ing. degree. At present, he is a PhD student. As it is shown on the figures 10-13, the parameters obtained In March 2008, he received the certificate by measurements and by calculation with the program “Basic and advanced simulation using “Diagram” are identical. The statistical error doesn’t exceed QuickField software”. the affordable limits. Therefore, the program “Diagram” can Starting from 2006, he is working as a laboratory assistant and a scientific assistant in be used for operating characteristics. the Department of Electrical Machines and Apparatus of Riga Technical University. III. CONCLUSIONS Tel. +371 67089928, E-mail: [email protected] All motor’s performances, which determine its condition (starting, operating and control) is possible to obtain from experiments. But to do so, it is necessary to have corresponding equipment, a lot of time and energy, especially for high-power motors. That reasons causes difficulties for calculation of each performance while constructing a motor. From this point of view it is understandable that simulation of these performances is preferable. As it is presented on the figures 6 – 13, the program “Diagram” provides satisfactory results for motors with different nominal parameters. Thus, this program can be used in cases when direct measurements are impossible. This simulation allows substituting measurements with calculations, when is necessary to research different static modes.
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