Technical Articles

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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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12 Transformer Factory Tests Briefly Explained

Factory tests The remainder of the twelve factory tests are briefly summarized below. The details of the test set connections and formulas of some of the listed tests are already described in separatly published articles, and for the rest you are directed to ANSI/IEEE Standard C57.12.90 for these details. This list is not complete, there […]

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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 Components of Current Drawn by the DC Voltage Testing of Insulation

Current drawn by the insulation When DC voltage is applied to an insulation, the electric field stress gives rise to current conduction and electrical polarization. Consider an elementary circuit as shown in Figure 1 below, which shows a DC voltage source, a switch, and an insulation specimen. However, this current immediately drops in value, and […]

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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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Basics of DC Motors For Electrical Engineers – Beginners

General about DC motors Separate field excitation DC motors are still sometimes used for driving machines at variable speed. These motors are very easy to miniaturize, and essential for very low powers and low voltages. They are also particularly suitable, up to high power levels (several megawatts), for speed variation with simple, uncomplicated electronic technologies […]

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Procedure for Transformer Lightning Impulse Test

Purpose of the test The purpose of the impulse voltage test is to secure that the transformer insultations withstand the lightning overvoltages which may occur in service. Testing equipment Impulse generator Where: C1 – Impulse capacitor Rc – Charging resistor Rs – Series resistor Ra – Low-ohmic discharging resistor for switching impulse, Rb – High-ohmic discharging resistor for […]

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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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