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Transformers, image - Coggle Diagram
Transformers
Unique Selling Point
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Any voltage, high or low, can be obtained from the supply voltage, 230 V in Europe
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Components
The transformer, like the induction coil uses two coils wound round each other.
Unlike the induction coil, the transformer takes an AC current, which means that there is an EMF induced continually in the secondary coil.
The two coil windings are electrically isolated from each other but are magnetically linked through the common core allowing electrical power to be transferred from one coil to the other.
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Transformers have a soft-iron core, as soft iron concentrates magnetic flux, making magnetically more efficient.
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EMF Ratio
The ratio of the EMF in the secondary coil to the EMF in the primary coil equals the ratio of turns in the secondary to the primary.
If the secondary EMF is higher than the primary, the transformer is a ‘step-up’ transformer.
If the secondary EMF is less than the primary, it is a ‘step-down’ transformer.
However, a third condition exists in which a transformer produces the same voltage on its secondary as is applied to its primary winding.
Secondary Voltage
VP is the voltage on the primary coil,
VS is the voltage on the secondary coil,
NP is the number of turns on the primary coil
NS is the number of turns on the secondary coil
Power
Gain
Naturally, the power in the secondary can never exceed the power in the primary, and due to energy losses, it will always be less.
So if the secondary EMF is greater than the primary EMF, the secondary current will be less.
Rating
The power rating of a transformer is obtained by multiplying the current by the voltage to obtain a rating in Volt-amperes, (VA).
Ratio
In an ideal transformer (ignoring any losses), the power available in the secondary winding will be the same as the power in the primary winding, they are constant wattage devices and do not change the power only the voltage to current ratio.
Regulation
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The secondary voltage, V2, of a transformer will fall as the transformer is loaded.
The fall is caused by the resistance and reactance of the windings.
The regulation of the transformer is usually expressed as a percentage of the no-load secondary voltage, E2.
Copper Loss
The resistive losses, often called the copper loss, are found from the equation:
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