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Backup Power

Admin — Mon, 06 Apr 2009 06:09:33 +0000

Backup Power is also known as an Emergency Power System, Backup Power Systems are types of systems that may include generators, lighting and many other apparatus, to provide a backup of resources (power) incase regular power systems fail or incase of a crisis. Backup Power is by many different people / companies / industries around the world, these include: Residential Homes, Data Centre, Modern Naval ships, Scientific Laboratories, Telecommunications Equipment and one of the most important places where Backup Power is needed is in Hospitals. Hospitals greatly rely on the knowledge that should anything happen to their power system they have Backup Power in place. A hospital could not run efficiently with out it, if there was to be a power failure every single piece of medical equipment in a hospital would shut down. This could be minor things like computers or monitoring equipment… but in some cases this could be dangerous, if a patient was on a Life Support Machine that machine would fail rendering it useless and putting the patients life at risk. Every Hospital should have its own form of backup power, usually backup generators and large hospitals may even have multiple of these incase the unlikely incident of a backup Power system also failing.

The History of Backup Power

Backup Power systems can date back to as early as World War II, they were used on Naval ships. These Naval Ships were at danger of loosing the function of their steam engines during combat, the steam engines powered the steam driven turbines for the generator. In this case they used one or often more than one diesel engines to drive back up the generators. Early transfer switches were not automatic tho and they relied on manual operation. There would be two switches that would be placed horizontally, in line and the on position of the switch would be facing each other. A rod was placed in between the two switches and in order for the switch to function one source must be turned off, when switched off this moves the rod to the other side where the other source is turned on.

Control of the Backup Power System

To avoid a long supply of electric wires a central battery system with automatic controls is used, this is located in the power station building itself. This type of system is used for a 208 VAC Backup Power Systems. The central battery system of the Backup Power consists of lead-acid battery cell units, these make up a 24 or 12 VDC System, stand-by cells are also used each with its own battery charging unit. Voltage sensing units are also required and they must be capable of receiving 208 VAC. Incase the 208 VAV station supply fails an automatic systems is required, this automatic system must be able to signal and activate the emergency supply unit.

Nuclear Plants also require a for of Backup Power, however this is slightly different and is know as EDG’s (Emergency Diesel Generators).

About Author:
Daniel Owen writes about Back Up Power. To know more about Back Up Power, visit http://www.businessmagnet.co.uk

Types And Usages Of Abrasive

Admin — Sun, 22 Mar 2009 03:40:20 +0000

Abrasives are commonplace and are used in a wide range on domestic, industrial and technological applications, they are used extensively in these sectors. An abrasive is a type of material, it can often be a mineral. Abrasives are used to finish or shape a workpiece, rubbing the abrasive on the workpiece leads to part of the workpiece being worn away. When finishing a material it is often thought of as a means to polish the material to gain a smooth surface or even reflective surface, however some finishes require roughening as in beaded, matte or satin finishes.

Common uses for abrasives include the following:

Buffing
Drilling,
Grinding
Sanding
Polishing
Cutting
Sharpening

Abrasion is a term given rise by Abrasives describing a wound or excoriation, Abrasions can occur from strong contact with certain surface like: Stone, Concrete, Carpet and Wood.

The Mechanics of Abrasion

The difference in hardness between the Abrasive and the surface they are worked on is what allows the Abrasive to work, the Abrasive being the harder of the 2 substances. However any 2 solid materials that tend to rub against eachother will eventually wear eachother away. An example of this is the sole of a shoe, after decades it will eventually wear away wooden or stone steps that are repeatedly walked upon.

Abrasives – Manufactured

You will find abrasives come in different shapes and these are because they have different purposes. Natural Abrasives are often in the form of a rectangular block and often solid as dressed stone. Both synthetic and natural Abrasives can be found in a wide variety of shapes, they are often Coated or Bonded Abrasives including, Wheels, Blocks, Discs, Belts, Rods, Loose Grain and Sheets.

Coated Abrasives

The most common type of Coated Abrasive is Sandpaper, a Coated Abrasive is an Abrasive fixed on to a form of backing material like paper, metal, rubber, resin, cloth and polyester. Coated abrasives tend to use the same minerals as Bonded Abrasives. A bonding agent like a resin or an adhesive is applied to the flat surface (paper for example) in which the mineral is applied, this forms the grit like surface of sandpaper.

Coated abrasives are often shaped for a specific purpose like to wrap around hand pads or sanding blocks, they can also be shaped for use in orbital or rotary sanders. The striking surface of a matchbox is a good example of how an abrasive can be used, Belt grinders are also another form of abrasive.

Bonded Abrasives

The most common abrasive used here is Aluminium Oxide, Bonded Abrasives are an Abrasive material contained within a matrix. A sharpening stone is a Bonded Abrasive; these tend to be in the form of a block with both sides having different densities of grit.

Another type of Bonded Abrasive is a Grinding Wheel, this is a cylinder that is rotated at a very high speed the cylinder has an Abrasive surface in with the material to be finished is pressed against whle it spins.

About Author:
Daniel Owen writes about Abrasives. To know more about Abrasives, visit http://www.businessmagnet.co.uk

AC-DC Power Supplies And Currents

Admin — Sun, 22 Mar 2009 03:38:20 +0000

Power Supplies can be divided into two types for electronic devices, linear and switching power supplies. A switching mode power supply has the same rating as a Linear Power Supply but will be a lot more complex and usually Switching Mode Power Supplies are smaller. A Linear Power Supply is used for high current devices. They tend to be a lot bigger and bulkier than the Switching Mode Power Supply and a lot simpler in design.

Linear Power Supplies powered by AC tend to require the use of a transformer to convert the voltage from the mains outlet to a different voltage, this tends to be converted to a lower voltage. However a Rectifier is needed if it is used to produce DC, In addition a capacitor will be used smoothing the pulsating current from the rectifier. AC Power Frequency’s relate the frequency the pulsations occur at (a multiple of 50Hz or 60Hz is a good example).

An unregulated power supply will produce a varying voltage depending on the variations and on the load of the AC Supply Voltage. A Linear Regulator will be used for critical electronics applications, the Linear Regulator will adjust and stabilise the voltage. When a Linear Regulator is used with a DC current it will greatly reduce the noise and ripple in the output of the current. They can also protect the Power Supply from overcurrent due to current limiting.

The AC supply in series with a single resistor and diode form the simplest DC Power Supply Circuit, these are very common in the use of rechargeable flashlights.

AC stands for Alternating Current, in Alternating Current the flow of electric charge reverses direction periodically, for instant an AC Current will move forward the backwards over and over again repeating the cycle of movement.

Electricity that is delivered to Residences and Businesses is in the form of AC Electricity. A ‘Sine Wave’ is the usual waveform of an AC Circuit; different waveforms can be used in different applications tho such as: Square Waves or Triangular Waves. Another example of an alternating current is electrical wires passing audio and radio signals.

DC stands for Direct Current and this is the unidirectional flow of electric current. Batteries, Solar Cells and Thermocouples are a few examples of sources that produce Direct Current. Semiconductors, Vacuum (Ion or Electron), insulators and wires are examples of conductors that DC (Direct Current) can flow through. Direct Current was formally known as Galvanic Current.

By use of a Rectifier, a Direct Current can be obtained from an Alternating Current. The rectifier contains electromechanical elements that will only allow the current to flow in one direction.

Nearly all electronic Power Supply Systems used Direct Current, it is also the current used to charge batteries. Electrochemical processes and the production of aluminium use very large amounts of direct current power supply, railway propulsion also requires a DC Current.

AC DC Power Supply is a very important source of power in the world we live in and many applications require them.

About Author:
Daniel Owen writes about AC-DC power Supplies. To know more about AC-DC power Supplies, visit http://www.businessmagnet.co.uk