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Generators:Standards.

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August 03, 2015

Standards

The leading international, regional and national standards adopted by users and sup- pliers of generators for manufacturing and testing are shown in Table 5.4.

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Power Electronics:Thyristor Devices

September 08, 2015

Power Electronics Introduction The modern age of power electronics began with the introduction of thyristors in the late 1950s [1]. There are now a number of power devices available for high-power and high-frequency applications. The most notable include: • Gat e turn-off (GTO) thyristor • Power Darlington transistor • Power MOSFET • I nsulated-gate bipolar transistor (IGBP) These power devices are used primarily as switches to convert energy from one form to another. They are used in motor control systems, uninterruptible power supplies, high-voltage dc transmission, ac-to-dc power supplies, induction heating, and other power-conversion applications. Thyristor Devices The thyristor, also called a silicon-controlled rectifier (SCR), is basically a four-layer three-junction pnpn device [1]. It has three terminals: anode, cathode, and gate. The device is turned on by applying a short pulse across the gate and cathode. After the device turns on, the gate loses its control t...

Power Factor:PF Correction Techniques

September 08, 2015

PF Correction Techniques The term compensation is used to describe the intentional insertion of reactive power devices, either capacitive or inductive, to achieve one or more desired effects in an electric power system. These effects include improved voltage profiles, enhanced stability, and increased transmission capacity. The devices are either in series or in shunt (parallel) with the load(s) at one or more points in the power circuit. To keep the power factor as close as possible to 100%, utility companies place capacitor banks in par- allel with the load at various locations in the distribution system, offsetting the inductive loading (lagging power factor) of most user equipment. The goal is to create an equal amount of leading PF in the system to match the lagging PF of the load. When balanced, the power factor is 100%. In practice, this is seldom attainable because loads are switched on and off at random times, but utilities routinely maintain an overall power factor of appr...

Grounding Practices:Terms and Codes and The Need for Grounding.

September 10, 2015

Introduction The attention given to the design and installation of a facility ground system is a key element in the day-to- day reliability of the plant. A well-designed and -installed ground network is invisible to the engineering staff. A marginal ground system, however, will cause problems on a regular basis. Grounding schemes can range from simple to complex, but any system serves three primary purposes: • Provides for operator safety • Protects electronic equipment from damage caused by transient disturbances • Diverts stray radio frequency energy from sensitive audio, video, control, and computer equipment Most engineers view grounding mainly as a method to protect equipment from damage or malfunction. However, the most important element is operator safety. The 120 or 208 Vac line current that powers most equipment can be dangerous — even deadly — if handled improperly. Grounding of equipment and structures provides protection against wiring errors or faults that could enda...