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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
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
Options contract is the contract between parties in which, a buyer has the right to sell or buy a particular asset at future date on agreed price. These types of contract are used in securities, commodities etc.In this, buyer will look at ask price and if he wants to buy into option contract, he will offer the bid price (which is lower than bid price). After the contract is purchased from the seller, a position is opened and seller is paid to buy an asset on strike price. Buyer has to sell, buy or exercise the contract before an expiry ... Read More
Swap curve is the relationship between swap rates and varying maturities. This curve tells about the expected returns at different maturity dates. It is a two dimensional curve in which, Y-axis represents the swap rates and X-axis represents maturity dates.These curves are calibrated and constructed in segments depends on market prices of different fixed income. The short end (not more than 3 months) swap curve is calibrated to unsecured deposit rates. Middle end (in between 3 months to 2 years) is derived in combination of interest rate futures and forward rate agreement contracts.Long term (more than or equal to 10 ... Read More
DeflationIt is decline in goods/services price when rate of inflation falls below zero percentage. It is linked to unemployment and productivity levels of goods/services are low. Deflation acts as economy indicator for deteriorating conditions.Causes of deflation are as follows −Structural changes (capital markets)Productivity increasedWhen decrease in currency supplyEffects of deflation are −Reduces business revenueLow wagesLayoffsDisinflationIt is nothing but decrease in rate of inflation or price inflation is slowing. It is a point where inflation increases at slower rates. Money supply slows down because of tighter monetary policy is cause of disinflation. Disinflation is not always a negative. It can be ... Read More