International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------Implementation of Single and double stage control of DC traction motor using matlab M. Devarajan, PG student, Kingston engineering college, vellore, India *Corresponding Author's E-mail: [email protected]

Abstract This paper describes about the single and double stage control of DC traction motor. DC series motors provide excellent control of speed for acceleration and deacceleration and it is used for their simplicity, each of application and favourable cost still in indian country most of the locomotive run with DC motor only because DC series motor is high starting torque with load hence it is preferable for traction purpose. In this case describes controlling of single and double stage of DC series traction motor. The simulation and experimental results is done by using MATLAB software package.

Keywords: single stage, double stage, dc series motor, traction.

I. INTRODUCTION The first railways were powered by steam engines. Although the first electric railway motor came on the scene halfway through the 19th century, the high infrastructure costs meant that its use was very limited. The first diesel engines for railway usage were not developed until halfway through the 20th century [1]. The evolution of electric motors for railways and the development of electrification from the middle of the 20th century meant that this kind of motor was suitable for railways. Nowadays, practically all commercial locomotives are powered by electric motors.

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------

Figure 1: General layout of electric locomotive

In electric motor technologies applied to rail traction consist of DC type and inverter driven AC type induction or synchronous. Those technologies have been sufficiently effective for rail traction systems. DC series motor is most effective for traction purpose because compare to AC speed control is easy and cost also less. In electric traction, like in other applications, a wide range in speed and torque control for the electric motor is desired. The DC machine fulfills these requirements, but this machine needs periodic maintenance [3]. Traction motor is the most important part of any locomotive converting electrical energy into mechanical requiring sturdiness of electrical, mechanical, magnetic and insulation system for safe and reliable function. In DC series motor is most widely used and about 80% motors in use are in this motor in indian country. DC electric motors usually work under 3KV supply and AC traction motor under 25KV.A general circuit of electric locomotive with DC series motor shown in figure 1.

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------

II. ELECTRIC TRACTION-OVER VIEW A. Traction mechanics The mechanics involves conversion of overhead electrical power in rail horse power to haul a train encountering acceleration, train, grade, curve resistance and similarly braking. Traction Mechanics involves concept of train resistance, tractive effort, braking effort, adhesion and balancing speed. The units followed in day to day talk of Railways are different as compared to conventional MKS system.

Table 1: Conversion table

ITEM SYMBOL RAILWAY MKS CONVESION

Time t hours 3600 sec Distance D kilometer 1000 meters Speed V kmph 0.277 m/sec Acceleration fa Kmph/sec 0.277 m/sec/sec Weight w tonne 1000 kg Force F kgf 9.8 newton Energy/work kWh kWh W-sec or N-M

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------

Figure 2: Electric traction locomotive

A figure 2 shows the general electric locomotive with traction motor.

B. Torque density Torque density is an important index for comparison of traction machines. Consider the basic equation of force on a conductor carrying current I of active length 1 in a magnetic field B is given

Force(F) = B*I*L Torque(T ) = B*I*L*r Where r is rotor radius, Current(I) = J*k*r Where J is the rotor 8surface current density, k depends on winding topology and number of poles then,

= B*J*k*Vm Where Vm is the magnetic volume of rotor and k is constant hence:

Torque density = B*J*k*

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------C. Power density Power is a product of torque and speed for a given torque density. Speed is constrained in DC machine due to commutation whereas it can go higher in synchronous and induction motor. This improves power density. Higher gear ratio is used to reduce speed at wheel end. Higher speed calls for designing of suspension arrangement to handle the issue of vibration and bearing lubrication.

III. DC SERIES MOTOR A. DC series motor for traction Components of series motor include armature that same current impressed upon the armature and the series field. The coil in the series field made few turns of large gauge wire to facilitate large amount of current flow. This provides high starting torque, approximately 2 times of rated load torque. Series motor armature are usually lap winding. Lap windings are good for high current low voltage applications because they have additional parallel paths to flow current [5].

Figure 3: DC motor with series field

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------Hence DC series motor preferred for traction purpose. A figure 3 shows DC series motor circuit and figure 4 shows seibu DC traction motor.

Figure 4: Seibu DC traction motor

To study features of traction power supply system and characteristic of traction load deeply, a simulation traction load for experiment and test is necessary. Generally some equipments are used as simulation traction load in lab, such as incandescent lamp, resistance and reactor, electromotor generator, and so on but here matlab software is used for traction simulation[6].

B. Dynamic model of dc series motor DC series motor, with its own characteristics of high starting torque which makes it suitable for high inertia as well as traction systems, has a nonlinear dynamical model. As its name indicates, the field circuit is connected in series with the armature and therefore the armature and field currents are the same. The equivalent circuit of a DC series motor is:

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------

Figure 5: Equivalent Circuit of DC Series Motor The equation of the armature:

Where Lf : field winding inductance, La : armature winding inductance, ia : armature current, V : applied voltage, Ra : armature winding resistance, Rf : field winding resistance, K : constants depends of the design of the machine, I : flux per pole, otational speed of the rotor. The motion equation is

Where J : rotor and load moment of interia and Tl : load torque, Here KI can be expressed in the function of Ia as :

Where E1 = -0.0017, E2 = 0.0938 and E3 = 0.0062. Substitute the values of KI in the above equation we get,

The final equation is,

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------This equation represents non linear dynamical behavior of DC series motor including the non linearity of the ferromagnetic material of the machine.

IV. SIMULATION AND RESULTS A. Single stage control of DC motor

Figure 6: Block diagram of single stage control Figure.6 shows the block diagram of single stage control of DC series traction motor. In this single stage control two traction motors are used and from 25KV AC supply it is stepped down using transformer.

Figure 6: Transformer input and output waveform

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------

Figure 7: Rectifier input The transformer input and output current, voltage as shown in figure.6. The input to the rectifier(i.e transformer output) as shown in figure.7. Rectifier converts AC/DC and it gives to the DC series traction motor.

Figure 8: Output waveform

The final output which is output of traction motor as shown in figure.8. The output is from two dc motor but in practical cases for each wheel of locomotive each motor will be connected.

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------

V. DOUBLE STAGE CONTROL

Figure 9: Block diagram of double stage control

Figure 10: Waveform of transformer input and output current

The block diagram of double stage control of DC traction motor as shown in figure.9. In this double stage control used four traction motors here 25KV is stepped down by using multi- winding transformer. A multi-winding transformer input and output current shown in figure.10. The regulated output gives to the each DC motor with snubber and rectifier.

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------

Figure 11: Snubber circuit output waveform

Figure 12: Uncompensated output motor control

Figure 13: Output of double stage control waveform

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International Journal of Mechatronics, Electrical and Computer Technology

Vol. 4(13), Oct, 2014, pp. 1404-1415, ISSN: 2305-0543 Available online at: http://www.aeuso.org © Austrian E-Journals of Universal Scientific Organization ------Snubber circuit removes unwanted disturbance it gives desired output to the motor the rectified regulated output voltage gives each traction motor. The rectified output circuit gives to DC motor gives to traction motor and the output as shown in figure 13. Here at the initial condition due to the disturbance oscillations are occurred shown in figure 13. Now the DC supply is given to the rated each of the traction motor.

CONCLUSION The simulation of single stage and double stage control implementation is proposed and the output characteristics of single stage and double stage are compared as shown in the waveform. In the simulation DC series motor is used still it is mostly used in railways because it gives excellent speed control, efficient and also gives high starting torque with load. Hence the DC series motor preferable for traction purpose. Here all simulations done by using MATLAB.

REFERENCES [1] Jose A. Lozano, Jesus Felez, Juan de Dios Sanz and Jose M. Mera, “Reliability and safety,” in railway, Dr. Xavier Perpinya (Edition) [Online]. Available: http://www.intechopen.com/books/ reliability-and-safety-in- railway/railway-traction. [2] How locomotive works a train, http://www.railelectrica.com. [3] Juan W. Dixon, Matías Rodríguez and Rodrigo Huert ,“ Simplified Sensorless Control for BLDC Motor Using DSP Technology,”pp.1431-1442. [4] Mohammad S. Widyan a, Anas I. Al Tarabsheh a, Issa Y. Etier a, Rolf E. Hanitsch,“ Transient Analysis and Output Characteristics of DC Motors Fed by Photovoltaic Systems,” in Jordan Journal of Mechanical and Industrial Engineering, Volume 4, Number 1, Jan.2010 ISSN 1995-6665, pp. 193 – 204. [5] Don shaw,“ DC motor analysis and troubleshooting,”. [6] Shaofeng Xiea, Jinbo Fenga, Gangyi Zhangb, “Study on simulation traction load with regenerative braking,” in 2011 2nd International Conference on Advances in Energy Engineering (ICAEE 2011), in Energy Procedia 14, pp.1299 – 1304.

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