Technical Articles

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Lightning and surge protection of multi-megawatt wind turbines

Importance of protecting wind turbines There is an unabated trend for the utilisation of regenerative energy gained from wind turbines, solar, photovoltaic and biogas plants or geothermal heat. This is an enormous market potential not only for the energy industry but also for the suppliers and the electrical trade and that worldwide. In Germany meanwhile about 19,000 wind […]

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8 NEC Basic Feeder Circuit Sizing Requirements

Feeder circuit loads Once the branch circuit loads are calculated, the feeder circuit loads may be calculated by applying demand factors to the branch circuit loads. General Lighting Loads (Article 220.42) Show window or track lighting (Article 220.43) Receptacles in other than dwelling units (Article 220.44) Motors (Article 220.50) Fixed Electric Space Heating (Article 220.51) […]

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Transformer Routine Test – Partial Discharge Measurement

Transformer insulation structure This routine test aims to measure the partial discharges which may occur in the transformer insulation structure during test. Partial-discharges are electrical arks which form the surges between electrodes of any area of the insulating media of a transformer between the conductors. These discharges may occur in air bubbles left in the […]

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Danger And Control Of Static Electricity Buildup

Troubles that you can run into… The following are the dangers posed by static electricity: Ignition causing fire or explosion Damage to sensitive electronic components Electric shock to humans followed by accidents such as a fall Damage to mechanical components such as bearings due to sparking through the oil films on bearing surfaces. It is necessary […]

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PLC Implementation Of Forward/Reverse Motor Circuit With Interlocking

Forward/Reverse Motor Interlocking Figure 1 illustrates a hardwired forward/reverse motor circuit with electrical and push button interlockings. Figure 2 shows the simplified wiring diagram for this motor. The PLC implementation of this circuit should include the use of the overload contacts to monitor the occurrence of an overload condition. The auxiliary starter contacts (M1 and […]

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Characteristics And Work Principles of Switched Reluctance (SR) Motor

SR Motor Characteristics The Switched Reluctance (SR) motor is very different from the other polyphase machines described because both the stator and the rotor have salient poles. The motor can only be used in conjunction with its specific power converter and control, and consequently only overall characteristics are relevant. The intuitively straight forward principle of […]

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Bonding of isolated, common and integrated grounding systems as a means of surge proofing

Clean vs Dirty Ground In this article we covered in detail the physics related to lightning phenomenon and how the surges due to lightning strokes are safely conducted to ground using a lightning protection system consisting of air terminations, down conductors and grounding electrodes. Both these grounding systems are inherently noise prone, since conduction of […]

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Providing capacitive reactive compensation with shunt capacitor banks

Few words about shunt capacitor banks Shunt capacitor banks are mainly installed to provide capacitive reactive compensation – power factor correction. The use of SCBs has increased because they are relatively inexpensive, easy and quick to install and can be deployed virtually anywhere in the network. Its installation has other beneficial effects on the system […]

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Electrical life (durability) of LV circuit breakers due to the switching operations

Test requirements According to the standard IEC 947-2, there is actually no defined stipulation regarding the requirements of electrical life of a circuit breaker. The numbers of switching operations which a circuit breaker under no-load, normal load, overload and short-circuit conditions has to make and/or break are stipulated. These numbers vary between two switchings (O-t-CO) […]

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The Most Typical Indices For Measuring Power Quality Disturbances

Power quality metrics There are various methods for categorizing the severity of power disturbances. The most typical indices for measuring power quality disturbances are listed and explained below: Distortion factor Crest factor Notch area Recovery time Displacement power factor Total power factor K factor 1. Distortion Factor The ratio of the root square value of […]

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