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TODAY IN HISTORY

    AMERICA'S FIRST ASPHALT PAVEMENT
    July 29, 1870

    Was laid in Newark, N.J. Previously, coal tar was used for many pavements laid in the 1860s. The first recorded asphalt pavement in the U.S. was a sand mix placed in front of the City Hall in Newark, N.J., in 1870. Edmund J. DeSmedt, a Belgian chemist (who became the inspector of asphalt and cements for the District of Columbia) held a U.S. patent for this asphalt paving method, granted on 31 May 1867. In that century most roads, even in cities, were wide dirt pathways, severely affected by weather. Smooth surfaced asphalt roads originally were for the benefit of bicyclists. By 1904, only 141 miles were surfaced, but commonplace by 1916. Natural asphalt deposits were originally used, but almost all of the asphalt used commercially is now made from petroleum.

    THE FIRST IRON LUNG
    July 29, 1927 - United States

    (Electric Respirator) was installed at Bellevue hospital in New York for the post war polio epidemic. The first iron lung was developed at Harvard University by Phillip Drinker and Louis Agassiz Shaw built with two vacuum cleaners. The iron lung is a negative pressure machine which surrounds the patient's body except for the head, and alternates a negative atmospheric pressure with the ambient one, resulting in rhythmic expansion of the chest cage (and thus inhalation) in response to the negative extra thoracic pressure. During periods of ambient extrathoracic pressure, the lungs deflate. This type of machine is rarely used today.

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Types Of Switchgear :

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ARTICLE INFORMATION :

Switchboards are used in many electronic applications. Do you know what switchgear is? What do small companies use to direct power where it is needed? Large power plants use switchboards to distribution power.

ARTICLE CONTENT :

There are two systems or panels that are used to redistribute power or electric current to other equipment or circuits. One is the switchboard and the other is switchgear.

Electric switchboards are a device that directs the electricity from one source to another. It is composed of an assembly of panels. Each panel contains switches to allow electricity to be redirected.

With a switchboard, a technician is protected from possible electrocution. The switches in the board control the amount of current that goes into the switchboard. Such switches are fed from a generator which has AC frequency and load sharing controls. It also has gauges that show the frequency and synchroscope.

It is important that the amount of electric power that goes into the switchboard is equal to the electric power going. When you take a look inside the switchboard, you will see a bank of busbars.

The busbars, which are generally bare and supported by insulators, are wide strips of copper that connect to switchgear. The busbars act to allow passage of large electric current through the switchboard.

Before the switchboard is opened for maintenance, it is important to isolate the power because the busbars are bare. These active busbars are a deadly source of power. When working on live switchboards, precautionary measures are crucial. Be ready with your protective equipment such as thick rubber mats and gloves, when working with an open switchboard.

Switchboards are isolated and protected with other equipment including substations, motors, high or medium voltage distribution networks and transformers.

Switchgear are also essential a type of electrical distribution device that is used to convert incoming electrical power into several smaller voltages. Switchgear can also be used as a circuit breaker.

There are many different types of circuit breaker switchgear. Vacuum circuit switchgear have minimal arcing. The arc quenches when it is stretched to less the 2 to 3 mm. They?re frequently used in modern medium-voltage switchgear of up to 35,000 volts.

If you need to de-energizing equipment, you can use switchgear. It also clears faults downstream and comes in varied parameters, which include number of panels, electrical specifications and mounting style.

The common types of switchgear are vacuum circuit breakers, oil insulated switchgear, gas insulated switchgear, and a simple open air circuit breaker. Oil insulated switchgear depend on an oil vaporization blast through its arc.

The gas insulated switchgear stretches the arc with a magnetic field and also depends on the dielectric strength of the gas to quench the stretched arc. The open air switchgear circuit breakers use compressed air to blow out the arc. The displaced air that tries to escape thus blows out the arc.

Circuit breakers are a unique type of switchboards that interrupts fault currents. Their design is especially made for interruption of fault currents.

The Classifications of switchboards are based on the current rating, the amount of interrupting rating, by voltage class, insulating medium, construction types, operating method, type of current, interrupting type, and application.

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  • November 30, 2014Date Added :
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