what are the types of current transformer ?

Types of CT:    

                   Irrespective of the types of CT due to core material selected more types of CT's are popular on the basic of their use and winding.

1. CT Wound Type:

          It is type of CT in which the primary winding of more than one full turns wound on the core. The wound types CT's are used for measuring current in a circuit of high voltage where a very precise dimension is not essential.

2. CT  Bar Type:

           It is CT in which the primary winding consists of a bar of suitable size and material forming an integral part of the CT. the current line on which we have to measure current is linked to the bar. This type of CT is suitable to measure high currents.transformer lamination manufacturer

3. CT Liquid Immersed:

              Ordinary CT'S are of dry type they do not require and oil or cooling medium other than   natural air for its operation.

but a special class of C's has been developed which require use of oil or other suitable liquid of suitable characteristics arequisitioning and closing medium. These types of CT's are used in switch yards and substations for the purpose of measurement and for connecting relays etc. for protection of the device

4. Hermetically sealed CT:

                  It is a liquid immersed CT which is sealed and does not communicate with atmospheric air. A casing of appropriate material is made which does not allowed the air to be in touch with CT.

5. Ring type CT:

             It is type of CT which has an opening in the centre to provide accommodations a primary conductor through it. In these types of CT's the core is wound only for secondary winding. The conductor passing through CT itself acts as primary winding. These are the most popular type of CT's. Because of their easy availability and ready to use property.

6. Multi core CT:

                It is CT having more than one secondary core and winding with a common primary winding.The different cores of such a CT are used to connect different relays and protective devises with it. Such as one core is used for determining current other is connected with differential protection relay.

7. Multi Ratio CT:

             It is type of CT in which more than one ratio is obtainable by reconnection, tapping’s etc. in primary or secondary winding. This is the advantage of this type of CT on others. It can be used for measuring a wide range of currents conferring to the measuring conditions.

What is Instrumental Transformer?

 Instrumental Transformer:

 

The instrument transformer are special type of transformers these transformers are defined as the transformer intended to supply measuring instruments, meters, relay and other similar apparatus.

In the measuring large current in a do circuit current and voltage is measured by using low range ammeter with a suitable shunt. For measuring high voltage high resistance is used in parallel.

For AC circuit capacities especially for high voltage measurement the simple instruments are not suitable as these are designed for low voltage. Also high rating instruments are not suitable on the economic point of view.

The measurement of these numbers is done with special device known as instrument transformers. These transformers or.  transformer lamination manufacturer  steps down current and voltage in definite proportion. This reduced quantity is measured with the help of low range ammeters and voltmeters and are then changed to actual value by knowing the transformation ratio of the transformer.

How to choose the Correct Coils for Transformer?

The reason rectangular and elliptical coils have been around for so long is that they work for certain standard applications and their construction favors high volume manufacturing processes.

If your need is truly for a standard distribution transformer subjected only to limited available fault currents, equipped with fusing or protection devices, subject to stable loading with little variation, or is a small to medium sized core transformer with star connected primary and secondary windings, then rectangular windings might work for you.

If on the other hand, your application is more "exposed" to higher levels of fault currents, repeated events, or high current requirements with lower designed impedance, like motor starting, the answer is yes you should buy a layer wound, round coil design and preferably one with robust bracing incorporating heavy duty pressure plates to add axial stability to counteract the strong physical forces experienced during faults.

Unlike wound cores, as are typically used with rectangular or elliptical coils, round coils allow for the utilization of miter cut, cruciform cores. Cruciform cores are comprised of multiple width lamination which, when assembled present a round cross-section and largely fill the core window in the round coils. Round coils with a cruciform core provide superior resistance to radial forces to which the transformer is subjected during faults and severe duty cycles.

The improved cooling available with the round coil construction also helps dissipate short circuit thermal effects after the fault has cleared and the Transformer Lamination Manufacturer resumes normal loading. The improved cooling is possible because, unlike wound cores, cruciform cores in conjunction with specially designed upper and lower pressure plates allow the cooling fluid to flow throughout the coils thereby substantially reducing hot spots in the insulation system, which in turn leads to longer transformer life expectancy.

If your purchases include larger transformers, 10 MVA and above, or higher BIL levels, 350 kV BIL and above, you should also consider buying disc-wound, round coils. The disc-wound design and construction gives all the benefits of layer wound round coils with miter cut cruciform cores and even more mechanical strength and transient fault withstand capability.

Furthermore, the disc construction minimizes electrical stresses within the coil caused by switching surges, lightening strikes, and voltage disturbances frequently found in the network at higher voltage levels and seen by larger transformers.

It is our recommendation that for most substation applications, for essentially all station transformer applications, and for those high-risk distribution transformer applications, you should buy wisely and purchase the round coil design for lower total cost of ownership.

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What re the Benefits of Lamination:

As far as finishing touches to printed materials go, few are more useful than lamination. Lamination is one of the simplest ways to keep printed documents looking pristine for longer. Laminating documents also gives them a professional finish and protects them from damage. These two factors combined present an attractive option to anyone wanting to get the most out of the documents they use.

Lamination is an ideal finishing option for a number of document types and any good printing company will usually offer laminating services, often as an add-on to make a professionally printed item look extra-polished. It is worth investigating the types of laminated finish that are available, ensuring the right finish is selected to do the print job justice.

Some of the best uses of lamination are as follows.

Poster lamination

Laminating a printed poster can turn it from a simple message into a durable sign. Poster lamination is of particular use for signs that need to be displayed over a long period of time, or that are displayed somewhere that they could easily be damaged. An example is the health and safety poster, which is displayed in a kitchen where it could easily come into contact with water.

Pass lamination

Passes or name badges that are printed onto standard paper can be made to last over a period of time by laminating them. This is particularly handy for businesses that have guests or visitors; a temporary visitor's security pass can be simply printed and laminated.

Business card lamination

Business cards are an essential part of entrepreneurial networking and cards are exchanged on a daily basis. One way to help a business card stand out from the crowd - and more prominently, retain its pristine condition even after expenses time in someone's wallet - is to get these business cards laminated.

Wipe-clean document lamination

Laminated documents make an excellent wipe-clean surface, ideal for writing on with a dry-wipe marker. This means booklets that change regularly, such as shift rotas and time tables, can be constantly updated without the need for reprints.

Lamination is technically defined as putting two layers of material together and the process has been around for a number of years. Curiously, the lamination process was invented in 1938 by a dentist, who created a process that would evolve to become what we know today as lamination. Lamination first became a popular way to preserve photographs that were originally printed on paper.

Today, laminating printed documents is commonplace, simply because lamination is a fast, effective way of protecting the printed element created. Transformer Lamination can protect documents from a variety of things, including saving documents from fading through sun damage to ensuring that they are no stained by dirt, dust or dampness. Any individual or organization looking to create printed material that can be reused or displayed for a long time would benefit from laminating their documents. This helps both time and budget to be utilized as effectively as possible.

Given the versatility of lamination, it is no surprise that many people see it as an essential part of producing professional-looking documents that have a long shelf life.

The author has worked in printing services and lamination for over 30 years. Lyndon writes for Minuteman Press UK; a print franchise organization. Read more here http://www.powercores.com/home.php