Found 189 Articles for Power Systems

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

In this article, we will throw some light on the different safety and protective devices used in electric elevators.Electric elevators 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. Therefore, it can be said that an electric elevator is an electrically operated device used for transporting at a fixed place.Safety and Protective Devices Used in ElevatorsThe elevator safety device is the part of elevator which is used for protecting the elevator so it can run safely. The primary ... Read More

In this article, we will take a look at the different types of electric motors used in the elevators. We will also discuss the suitability of different motors in different types of elevators, power calculation, starting torque requirements, and speed control methods of elevator motors.What is an Elevator Motor?An elevator motor is an electric motor which is used for up and down movements of elevator car. The turning force produced by the elevator motor is transmitted to the rope winding drum to wind or unwind the rope, so that the elevator car moves up and down.The elevator motors are specially ... Read More

The transition methods are defined as the methods of changing over the connections from one grouping to another. Depending upon the change over from full series to first parallel, the transition methods employed in the electric traction system are of the following three types −Open Circuit TransitionShunt TransitionBridge TransitionLet's discuss each of these transition methods in detail.Open Circuit TransitionThe steps involved in the open-circuit transition are shown in Figure-1. In case of the open-circuit transition, first the series connection between the motors is disconnected and power is switched off with full load current.Then, some of the starting resistance is reinserted ... Read More

This article is about AC generator and DC generator, and the main differences between the AC and DC generators.What is a Generator?An electrical machine which converts the mechanical energy input into electrical energy output is called the generator or electric generator.Though, the electrical energy generated by the machine can be of either AC (Alternating Current) or DC (Direct Current). Hence, based on the type of supply produced by the generator, they are of two types viz. −AC Generator (or Alternating Current Generator)DC Generator (or Direct Current Generator)Both of these alternators apply same principle (Faraday’s law of electromagnetic induction) to generate ... Read More

What is Tractive Effort?The effective force required for propelling a train at the wheel of locomotive is known as the tractive effort. It is denoted by 𝑭𝒕 and is measured in Newton. It is a vector quantity always acting tangential to the wheels of the locomotive.Tractive Effort for Propulsion of TrainThe total tractive effort required to propel the train on the track is equal to the sum of −Tractive effort required for linear and angular acceleration (𝐹𝑎).Tractive effort to overcome the effect of gravity (𝐹𝑔).Tractive effort to overcome the train resistance (𝐹𝑟).Therefore, the total tractive effort is given as, $$\mathrm{\mathit{F_{t}\mathrm{\: ... Read More

What is a Speed-Time Curve?Speed-time curves are the most convenient means of studying the movement of trains and their energy consumption. A speed-time curve is defined as the graph plotted between the speed and time, by taking speed (in km/hour) on the Y-axis and time (in seconds or minutes) on X-axis. The speed-time curve provides complete information of the motion of the train.The speed-time curve gives the speed of the train at various time instants after the start of the run directly. The slope of the curve at any point gives the acceleration at the corresponding instant or speed.The area ... Read More

Power Output from the Driving AxlesLet, 𝐹𝑡 = Tractive effort in Newton𝑉 = Speed of the train in kmphSince, the power output is defined as the work done per unit time, i.e., $$\mathrm{Power\: output, \mathit{P}\mathrm{\: =\: }Rate\: of \: work\: done\mathrm{\: =\: }\frac{Work \: done}{time}}$$$$\mathrm{\Rightarrow \mathit{P}\mathrm{\: =\: }\frac{Tractive\: effort\times Distance}{Time}\mathrm{\: =\: }Tractive\: effort\times Speed}$$$$\mathrm{\therefore \mathit{P\mathrm{\: =\: }F_{t}\times V}\: Nm/s}$$$$\mathrm{\Rightarrow \mathit{P\mathrm{\: =\: }F_{t}\times V}\times \frac{1000}{3600}\, Watts}$$$$\mathrm{\therefore \mathit{P\mathrm{\: =\: }\frac{F_{t}\times V}{\mathrm{3600}}}\: kW\: \cdot \cdot \cdot \left ( 1 \right )}$$Now, if 𝜼 is the efficiency of gear transmission, then the power output of motor (or power input to driving axles) is given ... Read More

In the plain rheostatic starting method, the voltage across the traction motor is gradually increased from zero to full line voltage and the current is kept constant at normal rated value by reducing the external resistance gradually.Let, 𝑇 = Starting period in seconds𝑉 = Line voltage in volts𝐼 = Constant current in amperesThen, at the instant of switching ON the supply, the back EMF produced by the motor is zero and it starts building up immediately as the motor starts rotating.At any instant, the supply voltage to the motor is equal to the back EMF developed by the motor plus ... Read More

In this article, we will take a look at the various methods used for starting and controlling the speed of DC series motors.Rheostatic ControlThe basic traction motor circuit with rheostatic starting is shown in the figure below.A DC series motor can be started by connecting an external resistance in series with the main circuit of the motor. At the starting instant, the back EMF developed by the motor is zero, thus the resistance connected in series with the motor is maximum and is of such a value that the voltage-drop across it with the full load rated current is equal ... Read More