Category Archive for: «Energy and Power»

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4 Main Means For The Generation Of Reactive Power

It’s all about reactive power… The four main means for the generation of reactive power are: Synchronous alternators Synchronous compensators (SC) Static var compensators (SVC) and Banks of static capacitors 1. Synchronous alternators Synchronous alternators are the main machines used for the generation of electrical energy. Besides, without going into technical details, by acting on […]

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Take Into Account the Losses When Purchasing Power Transformer

Transformer Price and Losses The Connection Losses and purchase price should be considered when deciding which transformer to purchase. The purpose of this technical article is to present a uniform approach that can be used to determine the dollar value of these losses over the life of the transformer. Below is typical wording of a transformer loss evaluation clause […]

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Example for Coordination of Cascaded Circuit Breakers

Inputs for Coordination Calculation A 440 V 60 Hz switchboard feeds a 4-wire distribution board for small loads such as socket outlets. The switchboard has a fault making capacity of 100kA rms. After applying diversity factors to the loads the total load current is 90 A. Moulded case circuit breakers (MCCBs) rated at 16 A […]

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Calculation of motor starting time as first approximation

Motor starting operations The problems connected to motor starting operations are fundamentally linked to the type of motor which a determined motor operational torque “CM” offers, to the starting modality and to the connected load which has a determined load torque “C ”. A generic curve of the above mentioned quantities is shown in the Figure […]

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5 Copper Busbar Jointing Methods

Efficient joints in copper busbar conductors Efficient joints in copper busbar conductors can be made very simply by: Bolting Clamping Riveting Soldering Welding Bolting and clamping are used extensively on-site. Shaped busbars may be prefabricated by using friction stir welding. 1. Bolted joints (most common) Bolted joints are formed by overlapping the bars and bolting […]

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When To Use a Solidly Grounded System?

Very low-impedance ground connection As is evident from the name, a solidly grounded system is one where the neutral of the system is directly connected to ground without introducing any intentional resistance in the ground circuit. A solidly grounded system clamps the neutral tightly to ground and ensures that when there is a ground fault […]

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Selective Coordination with Circuit Breakers

Introduction to Selective Coordination Selective coordination is often referred to simply as coordination. Coordination is defined in NEC® 240.2 as: “The proper localization of a fault condition to restrict outages to the equipment affected, accomplished by the choice of selective fault-protective devices.” The figure below shows the difference between a system without selective coordination and […]

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What Is Poor Power Quality?

Term “good power quality” Most electrical and electronic equipment is designed to operate from a power supply with a particular specification that usually defines the minimum and maximum limits for RMS (root mean-square) voltage and frequency. Electricity is unlike any other product in that quality cannot be assessed before delivery. It is used at the […]

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Understanding Transfer Switch Transition Types

Transfer sequence steps Transfer switches are used for quickly and safely transitioning all electrical power consumed by the circuit, equipment, or systems connected to the transfer switch output between those normal and emergency power sources. A typical transfer sequence includes following steps: The normal power source fails. When power from the generator or the backup utility […]

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Power distribution configurations with three three-phase hot power lines

Local distribution Power leaves the substation on three, three-phase “hot” power lines that are strung adjacent to highways or along local roads to points of use. All three phases share a single neutral line and have the same voltage, but they are 120 electrical degrees out of phase with each other. The local electrical utility […]

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