Category Archive for: «Energy and Power»

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The Philosophy Of Breaker Failure Protection

High speed protection scheme The separation of equipment into zones will only work successfully if the outputs of the protections can be guaranteed to do their job. This makes logical sense. For the bus protection in Figure 1 for example, the breakers X and Y must trip on a fault, otherwise the adjacent zone providing […]

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Few Aspects of Copper versus Aluminium

Conductor connections and terminations The constructions of aluminum wire and terminals have both been revised from past years. At one time the conductor was nearly pure aluminum, now they are all much stronger 8000 series alloys, with physical characteristics similar to copper. The wire terminations also have much more severe UL test requirements, resulting in […]

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5 Most Common Motor Load Types

Load profile (speed range, torque and power) Certain load types are characteristic in the industrial world. Knowing the load profile (speed range, torque and power) is essential when selecting a suitable motor and frequency converter for the application. Some common load types are shown. There may also be combinations of these types. Constant Torque Quadratic […]

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Important Guidelines To Startup and Shutdown a Large Generator

Operating Conditions // The purpose of this guidelines is to ensure the continuing operational integrity of generators. Operating conditions (startup and shutdown) that have forced units off-line or have damaged or shortened the life of turbine (or generator) components in the past are highlighted in the guideline to prevent recurrences in the future. Startup Operation […]

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Motor Connection for Clockwise and Counterclockwise Direction of Rotation

Star-delta (Y-Δ, wye-delta) starting Star-delta (in North America the designation “wye-delta” is commonly used instead) starting is the simplest method for reducing the starting current of a motor. The technique can be used with all squirrel-cage induction motors that are delta-connected for normal operation and whose windings ends are individually connected to terminals. The reduction […]

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3 Overcurrent Protective Device Ratings You Must Properly Select

Ampere, voltage and interrupting rating In order for an overcurrent protective device to operate properly, the overcurrent protective device ratings must be properly selected. These ratings include: Voltage rating Ampere rating and Interrupting rating - Minimum Interrupting Rating. If the interrupting rating is not properly selected, a serious hazard for equipment and personnel will exist. Current […]

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Single versus Parallel Generators – 7 Factors To Consider

7 factors to consider when deciding // Paralleling is the synchronous operation of two or more generator sets connected together on a common bus in order to provide power to common loads as shown in Figure 1. In deciding whether a single or multiple generators should be installed there are various factors to be considered, such as: Reliability […]

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Calculating The Short-Circuit Heating Of Busbars

Short-Circuit Effects Like all electrical circuits, busbars need to be protected against the effects of short-circuit currents. The open construction of busbars increases the risk of faults, e.g. by the ingress of foreign bodies into air gaps, and the risk of consequent damage is high due to their high normal operating currents and the amount […]

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Cable Sizing of Sub-Main Circuits – Working Examples

Few words about Sub-main circuits… A sub-main circuit can be defined as a circuit connected directly from the main LV switchboard to a sub-main distribution panel or a rising main for final connection of the minor current-using equipment. The Code requires that the maximum copper loss in every sub-main circuit should not exceed 1.5% of the total active power […]

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5 Types of equipment which generates the most harmonics

Non-linear loads // Harmonic load currents are generated by all non-linear loads. This includes: Switched mode power supplies (SMPS) Electronic fluorescent lighting ballasts Variable speed drives (VSDs) Uninterruptible power supplies (UPS) Magnetic-cored devices 1. Switched mode power supplies (SMPS) The majority of modern electronic units use switched mode power supplies (SMPS). These differ from older […]

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