"electric drives in traction system"
BY HANISH CHOWDARY.V VIGNAN’S INSTITUTE OF INFORMATION AND TECHNOLOGY VISAKHAPATNAM INTRODUCTION Electric traction makes things easier and safer. They bring down the distance and time and break the barriers of time and space. Electric traction is very economical, easy and safe. They can largely opt for vehicles, elevators etc CONTENTS: 1) Characteristics 2) Classification 3) Electric traction drives 4) Third Rail 5) Electronic CHARACTERISTICS: The main advantage of electric trains is the superior acceleration, due to the excess of power-to-weight ratio that can be obtained by modern electric trains. Other advantages include the lack of exhaust fumes at point of use, less noise and lower maintenance requirements of the traction units. Classification: VOLTAGE :- The common voltages are simple multiples of each other. 1200 V DC = 2 * 600 V DC 1500 V DC = 2 * 750 V DC CURRENT :- This can be DC or AC. For AC systems the frequency is also given. Contact System :- This refers to the means by which traction current is collected by the traction unit. Electric traction drives :- The DC traction motor : how it drives the motor NOSE SUSPENDED TRACTION MOTOR :- The motor case was provided with a “nose” which rested on a bracket fixed to the transom of the bogie. It was called a “nose suspended motor. Its main disadvantage is that part of the weight rests on the axle and is therefore unsprung. This leads to greater wear on bogie and track. Quill Drive :- Linear Motor :- The efficiency of the linear motor is about 60% of the conventional motor but it has the advantage of less moving parts and it does not have the reliance on adhesion of the conventional motor. Most electrification systems use overhead wires, but third rail is an option up to about 1200 V. The top speed of trains on third-rail systems is limited to 100 mph (160 km/h) Electronic Power :- DC gets up to 3000 volts, while AC uses 15,000 - 50,000 volts. DC motors have been the preferred type for railways because their characteristics were just right for the job. They were easy to control too. For this reason, even trains powered from AC supplies were usually equipped with DC motors AC Locomotives with DC drives : DC CHOPPERS :- i. It is a cheapest method ii. Maintenance and repair cost of electric traction is about 50% of that of steam traction system. iii. It has very high starting torque. High starting torque makes acceleration rate very high. i. Higher initial expenditure is involved in electric traction. ii. Failure of supply is a problem to be faced in electric traction. iii.The electrically operated vehicles have to move only on electrified track. CONCLUSION : Using these electric drives we can get better performance and by applying these electronic control methods we can easily control our electric traction motors. ANY QUERIES THANK YOU