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A transformer is a device that steps up, or steps down voltage. During this process current is also stepped up or down:however, voltage and current are inversely proportional ( meaning an increase in voltage results in a decrease in current and vice versa ) As an example: A step up transformer of 10:1 ratio with 12 volts and 10 amper of current applied to the primary will have ten times the voltage ( 120 volts ) and ten times less current ( 1 amrere ) at the secondary...and a step down transformer with the same turns ratio with 120 volts and 1 ampere applied to the primary will have 12 volts and ten ampere available at the secondary. The electricity supplied into homes and business uses wires carrying very high voltage and low current over long distances, then uses step down Transformers to step down the voltage and step up the current.

However, in power engineering and protective relaying applications, there are what are called "instrument transformers" which have the specific purpose of providing information to devices (such as relays or meters) about the voltages or currents in the power system. Therefore, there are some differences in construction and connectivity between a Current Transformer (CT) and a Voltage (or Potential) Transformer (PT).

A CT will typically have a toroidal core and evenly distributed secondary windings so as to minimize leakage reactance. The primary is typically the main power line conductor, which passes directly through the toroidal core. This type of transformer is specifically for the purpose of measuring current values, and the secondary windings cannot be left open-circuited, or a large voltage will be produce, resulting in dielectric failure (and often an explosion). If a device is not connected to the CT, its secondary must be short-circuited.

A PT is connected between the main conductor and ground and can be either wound in the normal way, or the voltage can be taken from a subsection of a string of capacitors (this is called a Capacitive Voltage Tansformer or CVT, and is usually cheaper than the wound type, but is typically not as accurate). This type of transformer measures voltage values, and the secondary winding cannot be short-circuited, as this will produce excessively high currents, resulting in the failure of the PT or the wires it is connected to. A PT can be left open-circuited.

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The incoming voltage from the source to the transformer is called primary voltage.


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The term 'constant voltage transformer' is used to differentiate the operation of transformers that are intended to change voltage levels, from those intended to change current levels -a current transformer (CT), for example, is termed a 'constant current transformer'.


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the incoming voltage from the current source to the transformer is called primary voltage.....


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Voltage Tarnsformer transforms only voltage. While power transformer transforms both voltage and current.


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A transformer. it steps up / down voltage, and steps down / up current.


What are the output voltage and current of a transformer determined by?

The secondary (output) voltage is determined by the primary voltage and the turns ratio of the transformer. The secondary current is determined by the secondary voltage and the load resistance.


A transformer can increase or deacrease what?

Voltage and current.


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A transformer can be used to change the voltage to an appliance. The voltage rating of the transformer should be right for the voltages used, and the current rating of the transformer should not be less than the current drawn by the equipment.


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