In this article, we will have a detailed discussion regarding electric drives, their types, and how AC Drives and DC Drives differ in their features.What is an Electric Drive?An electrical or electronic device which is used for controlling the speed of an electric motor is known as an electric drive. The electric drives are constant and variable speed controllers and extensively used in industrial automation and robotics. The basic block diagram of an electric drive is shown in the figure below.Based on the nature of electric current, the electric drives are of following two types −AC Drives (Alternating Current Drives)DC ... Read More

In this article, we will take a detailed look at the various features of AC and DC motors and highlight their differences. An electric machine that converts electrical energy (either AC or DC) into mechanical energy is known as an electric motor. Based on the type of input electric supply, electric motors are classified into two types, viz. −AC MotorDC MotorWhat is an AC Motor?An AC motor is one that converts AC electrical power at input into mechanical power at output by using the principle of electromagnetic induction. The AC motor takes alternating current as the input. It consists of ... Read More

In this article, we will take a look at insulated overlap and uninsulated overlap, which are overhead equipment used in electric traction systems.What is an Overhead Equipment?Overhead Equipment (OHE) in electric traction system are used for transmitting electrical energy to the electric locomotives, trolley buses, trams and other electric traction systems.As in any electrical circuit, the series and parallel connections are made by twisting cables together, using junction box, soldering, brazing, etc. But, in case of overhead conductor wire (or catenary wire), the use of these equipment is not possible. Therefore, the arrangement employed for the same purpose in the ... Read More

What is an Electric Elevator?Electric elevatrors are the electrically operated devices which are used for lifting up and down, moving load in suitable direction, and lifts in multistoried buildings for facilitating up and down movements of occupants, etc. Therefore, it can be said that an electric elevator is an electrically operated device used for transporting at a fixed place.Types of Electric ElevatorsBased on different parameters, electric elevators may be classified into different categories as follows −Depending on the type of service:Passenger elevatorsFreight elevators – for stores, apartments and hotels, etc.Special elevators – for garages, side walk, etc.Combination of elevators – ... Read More

In this article, we will see how booster transformers are used in electric traction systems for reducing the interference with the communication systems. We will also take a look at the methods of connecting the booster transformer in a traction system.In AC traction systems, the return current mainly flows to the substation through the track. Some portion of this returning current flows through the earth because of leakage of current from the track to the earth. This leakage current causes a heavy interference with the neighbouring communication lines. Therefore, it is required to avoid this interference by some means like ... Read More

What is a Trolleybus?A trolleybus is an electric bus that draws its electricity from overhead wires, which are generally suspended from roadside posts, using spring loaded trolley poles. The trolleybus is also known as trolley coach or trackless trolley or trackless tram. The trolleybus is a pneumatic tyre vehicle.In case of trolleybus, two wires and poles are required to complete the electric circuit. It is fed usually at 600 VDC from the overhead contact wires by means of two collectors. In trolleybus drives, a DC compound motor of output of 50 to 100 kW is usually employed.The speed control in ... Read More

Specific Energy ConsumptionThe amount of energy input to the traction motors is known as energy consumption of the train. It is the energy consumed for the propelling the train. The total energy drawn from the distribution system is greater than this energy and is equal to the energy consumed by the various parts of the train and the quantity of the energy required for lighting, heating, control and braking, etc.This amount of energy consumed by the various parts of the train per ton per kilometer is termed as specific energy consumption and is expressed in watt-hours per ton per km. ... Read More

What is Pantograph Collector?The current in the overhead system is collected with the help of a sliding contact collector mounted on the roof of the vehicle. The pantograph current collector is used in the railways for collection of current from the overhead system where the operating speed of the train is as high as 100 kmph to 130 kmph and the current to be collected are as large as 2 kA to 3 kA.The pantograph is mounted on the roof of the vehicle and carry a sliding shoe for contact with the overhead trolley wire. It consists of a jointed ... Read More

When the train is accelerated up to a certain speed it requires energy, which is known as kinetic energy, corresponding to that speed. This kinetic energy is given by the expression, $$\mathrm{KE\mathrm{\: =\: }\frac{1}{2}\mathit{mv^{\mathrm{2}}}}$$During coasting period, a part of this stored energy is utilized in propelling the train against frictional and other resistances to motion of the train and hence the speed of the train decreases. Therefore, coasting may be considered as a form of mechanical regenerative braking.The saving in the energy consumption can be considerably affected by increasing the coasting but it will decrease the schedule speed of the ... Read More

What is Regenerative Braking?The method of braking in which no energy is drawn from the supply system during braking period and some of the energy (kinetic energy of rotating parts) is fed back to the supply system is known as regenerative braking.The regenerative braking is the most efficient method of electric braking to the driving motor of locomotives. The regenerative braking can be applied to both AC and DC motors.Advantages of Regenerative BrakingThe advantages of the regenerative braking include the following −In case of regenerative braking, a part of electrical energy is returned to the supply system, so the total ... Read More