Study of Multiphase Induction Motor Applicability in DC Electrified Conventional Railway
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Date
2022-03
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Addis Ababa University
Abstract
Power transmission to electric locomotives and railway vehicles can be carried out using DC
or single-phase AC networks. The utility company supplies the railway company with AC
voltage which can be used as either DC voltage or AC voltage depending on the different
factors. Propulsion is provided by induction (AC) motors in both cases.
Conventional three-phase induction motor have been seen as the standard for electrical
alternating current drives for industry and transport, although they have an inherent setback in
terms of performance with regards to the loss of phase conditions. In view of this loss of phase,
the three-phase induction engine does not provide sufficient operation, such as power output
and torque, as required in electrical traction and other applications. Thus, the Multiphase
machine has several advantages over the conventional three-phase motor such as costeffectiveness,
reduced torque pulsation, reduced harmonic current per rotor phase, high
reliability and high fault tolerance.
The same machine parameters were used to simulate the system in Matlab/Simulink software
using mathematical models to create the Simulink blocks in order to test the output of both
three and six phase induction motors in DC traditional railway traction system. The study of
the economical aspect of multiphase induction motor compared to three phase motor was also
carried out. The V/F motor speed control technique was employed, in which the frequency and
voltage decrease proportionally (their ratio remaining constant), while peak torque remains
constant, resulting in speed control and an increase in starting torque up to the motor's
maximum torque.
The distortion was shown to be higher in three phase motors than in six phase motors. The
torque in six phase IM was seen to be 1.86 times that of three phase induction motor while the
speed in three phase induction motor is 2.6 times that of six phase induction motor. The overall
impact of multi-phase systems yields in a small reduction in price (-11%) according to the
economic analysis of both motors.
As a result, using a multiphase induction motor in a DC railway would improve energy
efficiency, and cost savings, as well as help to increase traditional railway capacity i.e. the
number of trains that can travel over a given section of line during a given period of time.
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Keywords
railway, three phase induction motor, voltage source inverter(VSI), six phase induction motor, v/f control technic