DC shunt motors are not suitable for traction purpose, the reasons are given below: 1. The dc shunt motor is a constant speed motor and its speed-torque characteristic does not meet with the requirements of traction. i.e., the power drawn from supply mains varies directly as the load torque.
Which motor is used in traction?
AC traction motors have replaced DC motors in many traction applications. The motors used are induction or asynchronous motors designed to have characteristics suitable for traction. The speed and torque of the motor are controlled by varying the frequency, voltage and current applied to the stator coils.
Which of the following motors is used for traction purpose?
Explanation: DC motors are used for traction as, according to the characteristics of DC motors speed is inversely proportional to torque and square of armature current as well, if linear magnetization is concerned. Thus, DC motors are perfectly suitable for traction.
Which motor is used for traction purpose Mcq?
For electric traction, DC series motors are best suited. DC series motors and AC series motors are very much recommended, as they provide a high starting torque Nowadays three-phase induction motors are also being used.
Which type of DC motor is used for traction?
Traditionally, these were series-wound brushed DC motors, usually running on approximately 600 volts. The availability of high-powered semiconductors (thyristors and the IGBT) has now made practical the use of much simpler, higher-reliability AC induction motors known as asynchronous traction motors.
Are locomotives AC or DC?
Depending on the design of the train, it can either produce AC or DC current using a generator powered by the diesel engine. Because of various electrical connections, multiple locomotives can be operated by a single lead until operated by a single crew.
Why regenerative braking is not possible in DC motor?
In case of DC Series motor, as the speed of Motor increases, the armature current and hence the field flux will decrease and therefore Back emf E can never be greater than the supply voltage V. Therefore, Regenerative Braking is not possible in DC Series Motor.
What are the general features of traction motor?
Salient Features of Traction Motors
- Designs equipped with brush-rocker assembly, terminal box and axle roller suspension bearings.
- Polyimide film covered conductors for armature coils.
- Armatures built with high permeability electrical sheet steel.
- Potted field coils for better heat dissipation.
What is the meaning of traction system?
The traction system is a component of the train. It is a system installed on the roof or underneath the train. The traction system converts the electrical energy, collected from the catenary via the pantograph, into mechanical energy, thus enabling the wheels to turn and, therefore, the train to accelerate and brake.
What is traction inverter?
Traction inverters convert dc power from an on-board high voltage (HV) battery into ac power to drive the main motor or motors of an electric vehicle. In addition, traction inverters perform functions such as voltage boosting, switch protection and regenerative braking.
Which braking is not suitable for motors?
In series motor back emf cannot exceed the supply voltage. So regenerative braking is not possible.
Which motor is more efficient Mcq?
Two pole motor has better efficiency. Two pole motor has better rpm and noise performance.
Which motor is not suitable for regenerative braking?
Regenerative braking is not possible in a series motor. Explanation: In regenerative braking, the motor acts as a generator. The back emf is more than the terminal voltage in case of regenerative braking. 2.
Why is dc series motor is suitable for traction?
DC series motor has been the most used solution for the traction of locomotives, trolleybuses, trams and others, characterized by a speed and torque control using additional resistances, which means a low efficiency, electromechanical contactors, high maintenance costs, dynamic braking in resistances.
Are diesel locomotives AC or DC?
In a diesel–electric locomotive, the diesel engine drives either an electrical DC generator (generally, less than 3,000 horsepower (2,200 kW) net for traction), or an electrical AC alternator-rectifier (generally 3,000 horsepower (2,200 kW) net or more for traction), the output of which provides power to the traction …
Why Interpoles are used in DC machine?
Inter poles in dc machines help to reduce armature reaction effects in the inter polar regions and their windings are connected in series with the armature so that its effect can vary with the armature current.