Single Phase Transformers

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Question1

a low voltage winding connected in delta or in star connection?

Star

Question2

A Magnetic field can Produce by what?

Coil

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Introduction

A transformer is a device for increasing or decreasing an AC voltage.

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Constructional Features of Single-Phase Transformers

A transformer consists of two coils of wires known as primary and secondary windings.

Where:

• VP - is the Primary Voltage

• VS - is the Secondary Voltage

• NP - is the Number of Primary Windings

• NS - is the Number of Secondary Windings

• Φ (phi) - is the Flux Linkag

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Constructional Features of Single-Phase Transformers

A single-phase transformer can operate to either increase or decrease the voltage applied to the primary winding.

1) When a transformer is used to “increase” the voltage on its secondary winding with respect to the primary, it is called a Step-up transformer.

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Constructional Features of Single-Phase Transformers

2) When it is used to “decrease” the voltage on the secondary winding with respect to the primary it is called a Step-down transformer.

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Constructional Features of Single-Phase Transformers

3) a third condition exists in which a transformer produces the same voltage on its secondary as is applied to its primary winding.

This type of transformer is called an “Impedance Transformer”

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According to the design, transformers can be classified into two:

1. Core- Type Transformer. 2. Shell-Type Transformer.

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Oil Filled Self-Cooled Type.

Oil Filled Water Cooled Type.

Air Blast Type.

According to the type of cooling employed

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Question

On the outside of the transformer there are components what are the function of them?

1. Some help it to remain at a good working temperature.

2. Some help make it safer in the event of accident.

3. Some are used for monitoring.

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Theory of Operation The operation of a transformer is based on two principles:

1. A voltage is induced in a conductor when the conductor passes through a magnetic field.

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2. A current passing through a conductor will develop a magnetic field around the conductor.

Theory of Operation

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Question

True Or FalseThe winding which is connected to the supply mains is known as Secondary winding ( × )

The winding which is connected to the load is known as Primary winding ( × )

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Ideal of Transformers • Two magnetically coupled coils

• Primary: N1 turns

• Secondary: N2 turns

• Primary and secondary can be arbitrarily assigned

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Ideal of Transformers

Ideal assumptions

• No flux leakage.

• No eddy currents. Recall from magnetic circuits lecture

• No winding resistance.

• Near infinite core permeability.

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EMF equation and transformation ratio.

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Voltage Transformation Ratio (K)

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1. A 50Hz transformer primary voltage of the screw 300 and 5000, determining the taxa. Mutual flux Φm.b. If the 230 V secondary voltage of the secondary screw.Are,ƒ = 50Hz has been invokedNp = 5000 Qm =?Ep = 2300 Volt Ns =?Es = 230 Volt

A. Ep = 4.44 ƒNpΦ

Φ = Ep / 4.44ƒNp

= 2300/4.44 × 50 × 5000

= 2.09 mweb. Ans.

B. Es = 4.44 ƒNsΦ

Ns = Es / 4.44ƒΦ

= 230 / 4.44 × 50 × 2.09mweb

= 500 Ans

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