11. Traction Motor (Three Phase Induction Motor):
Motor coach of metro train has four traction motor per coach i.e. one traction motor on each axle. Similarly, locomotives have one traction motor on each axle. In a metro train, the number of motor coaches may be 33 to 66% of the total number of coaches. With Variable Voltage Variable Frequency (VVVF) Control, squirrel cage three phase induction motors of about 250KW are used in metro train. Generally, each three phase PWM converter feeds two three phase induction motors connected in parallel. In case of fault in any traction motor, the concern PWM converter and connected two traction motor get switched off automatically, while remaining propulsion system work normally. The three phase PWM converter have harmonics content in the output voltage, which lead to overheating of traction motor. During the train operation, traction induction motors are operated with its short time rating, a wide range of frequency & speed, which make its design much complicated as compared to general purpose induction motor. During the train operation, traction motors are operated in following four quadrants:
Motor coach of metro train has four traction motor per coach i.e. one traction motor on each axle. Similarly, locomotives have one traction motor on each axle. In a metro train, the number of motor coaches may be 33 to 66% of the total number of coaches. With Variable Voltage Variable Frequency (VVVF) Control, squirrel cage three phase induction motors of about 250KW are used in metro train. Generally, each three phase PWM converter feeds two three phase induction motors connected in parallel. In case of fault in any traction motor, the concern PWM converter and connected two traction motor get switched off automatically, while remaining propulsion system work normally. The three phase PWM converter have harmonics content in the output voltage, which lead to overheating of traction motor. During the train operation, traction induction motors are operated with its short time rating, a wide range of frequency & speed, which make its design much complicated as compared to general purpose induction motor. During the train operation, traction motors are operated in following four quadrants:
12.Auxiliary Converter:The auxiliary converter is used to supply auxiliary load of the train. It is connected either from the DC link or additional auxiliary winding provided in main transformer for auxiliary load. It consists of IGBT based inverter, isolation transformer, sine wave filters and switchgear devices. Sine wave filters are low pass frequency filters, which convert the rectangular pulse width modulated (PWM) output of auxiliary converter into a smooth sine wave voltage. The output of auxiliary converter are 3-Phase 415V supply, 1- Phase supply and 110V or 24V DC supply; which are used to feed the load of cooling blowers, battery charger, control electronics and light & fan load etc.
13.Variable Voltage Variable Frequency (VVVF) Control :
13.Variable Voltage Variable Frequency (VVVF) Control :