MBB2083-EXP 1 Transformer

8/2/2019 MBB2083-EXP 1 Transformer

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EXPERIMENT 1: TRANSFORMERS

MBB2083 - ELECTRICAL POWER & MACHINES (LAB)

MECHANICAL ENGINEERING PROGRAM

INSTRUCTION MANUAL

1. TRANSFORMERS LABORATORY

1.1 MEASUREMENT OF THE TRANSFORMER WINDINGSRESISTANCE

1.1.1 OBJECTIVES

Measure the primary and secondary windings resistance of single phase transformerswith the Volt-Ampere method (Ohm's Law).

1.1.2 THEORETICAL REVIEW

The transformers' windings resistance cause internal voltage drops that reduce theirefficiency. Therefore, it must be as low as possible. It is calculated by applying known DCvoltage and measuring the resulting current flow.

1.1.3 FORMULAE

PARAMETER SYMBOL UNIT

Winding Voltage V VoltsWinding Current I Amperes

Winding Resistance R Ohms

R=V/I for single phase transformer

R=V/I * 2 for STAR connected three phase transformers

1.1.4 COMPONENTS

Single Phase Transformer Model A4110Power Supply Model A0240Cables Model A4890

Cables Support Model A4891Ammeter (A) With adequate range for this testVoltmeter (V) With adequate range for this test

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INSTRUCTION MANUAL

1.1.5 CIRCUIT DIAGRAMS

Theoretical DiagramSingle Phase Transformer

Primary Secondary

PS3

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A

V

+

_


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INSTRUCTION MANUAL

Execution Diagram

ELWE POWER SUPPLY

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A

A4110

V


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INSTRUCTION MANUAL

1.1.6 EXECUTION

The components must be connected as shown in the circuit diagrams and must begrounded.

MANUAL DATA COLLECTION AND ANALYSIS

- Set the DC windings voltage PS3 = 0 V.

- Switch on the power supply.Increase input voltage gradually by operating on the front knob power supply. It mustbe increased in 2% steps up to 10 % max.Do not exceed 10 % of nominal winding voltage to avoid overheating of the windings.

- Measure the voltage and current for any step and enter them in the worksheettables.

- Repeat the above steps for all primary and secondary windings and calculate theirresistance with the formulae given above.

- Now calculate the average value of the resistance for each primary and secondarywinding. Similar windings should have similar resistance.

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INSTRUCTION MANUAL

1.1.7 WORKSHEETS

Parameter Symbol Unit Value

PRIMARY

Winding Voltage % 2 4 6 8 9

Winding Voltage V V

Winding Current I A

Winding Resistance R

SECONDARY

Winding Voltage % 2 4 6 8 9

Winding Voltage V V

Winding Current I A

Winding Resistance R

Winding Voltage V V

Winding Current I A

Winding Resistance R Transformer Model:

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INSTRUCTION MANUAL

1.2 MEASUREMENT OF THE TRANSFORMATION RATIO

1.2.1 OBJECTIVES

Calculate the transformation ratio of single phase transformers.


The transformation ratio is a characteristic value of every transformer and can becalculated either as a ratio between primary and secondary windings turns or voltages. Itis therefore >1 in a step-down transformer and


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INSTRUCTION MANUAL


Theoretical Diagram

Single Phase Transformer

Primary Secondary

PS2

Execution Diagram

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V1 V2


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INSTRUCTION MANUAL

Elwe Power Supply

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A4110

V1V2


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INSTRUCTION MANUAL

1.2.6 EXECUTION



- Set the AC input voltage PS2 or PS1 = 0 V.

- Switch on the power supply.Increase the input voltage gradually in 20% steps from 0% to 100% of transformersnominal voltage

- At each step measure the voltage readings of V1 and V2 and enter them in theworksheet tables.

- At each step compute the transformation ratio with the formulae given above andenter them in the worksheet tables.

- At this point calculate the average value of the transformation ratio.

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INSTRUCTION MANUAL

1.2.7 WORKSHEETS


Input Voltage % 20 40 60 80 100

Primary Voltage V1 V

Secondary Voltage V2 V

TransformationRatio K

Transformer Model:

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INSTRUCTION MANUAL

1.3 SHORT CIRCUIT TEST

1.3.1 OBJECTIVES

Calculate the resistance losses, determine the short circuit voltage and the short circuitpower factor, calculate the additional losses, the equivalent resistance and reactance.


With this test the transformer primary windings are fed with up to the nominal currentand the secondary windings are short-circuited. The power drawn is very low andtherefore it is possible to simulate the leakage fluxes in both primary and secondarywindings because the latter depends upon the load current in the two windings.

As the transformer is short-circuited, the input voltage must be very low, usually 5% ofthe nominal rating and the mutual flux is of the same order of magnitude. Since the corelosses are approximately proportional to the square of the mutual flux, they arenegligible.

This means that a wattmeter connected to measure the input power indicates only thecopper losses because there are no output power or core losses.

1.3.3 FORMULAE


Voltage V VoltsCurrent I AmperesInput Power W Watts

Single phase transformers: P = W

Cos = P/(V *I)I = P/(V* Cos )R = P/I2

Z = V/IX = Z2 - R2

1.3.4 COMPONENTS

Single Phase Transformer Model A4110Three Phase Transformer Model A4120Power Supply Model A0240Cables Model A4890

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INSTRUCTION MANUAL

Cables Support Model A4891Ammeters (A) With adequate range for this testWattmeters (W1, W2) With adequate range for this testVoltmeter (V) With adequate range for this test


Theoretical Diagram


Primary Secondary

PS2

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W1

V

A


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INSTRUCTION MANUAL

Execution Diagram

A0240 Section PS1 Sections PS2 - 3Section PS4

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V A

A

ACDC

> 230V> 24V

0v

220v

0v

160v

0v

110v

220v

Transformer

DigitalMultimeter

Power supply


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INSTRUCTION MANUAL

1.3.6 EXECUTION

The components must be connected as shown in the diagrams and must be grounded.



- Switch on the power supply.Increase the input voltage at 1% steps to about 5% of nominal rating until thenominal current can be read in the primary winding.

- At each step enter the readings in the worksheet tables.

- At the end calculate the Equivalent Secondary Reactance, Impedance and Resistancewith the above formulae.

- Plot the graphs

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INSTRUCTION MANUAL

1.3.7 WORKSHEETS


Input Voltage % 1 2 3 4 5

Winding Voltage V V

Current A A

Wattmeter W W

Power Factor Cos Reactance

Impadance

Resistance

Transformer Model:

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INSTRUCTION MANUAL

1.4 NO LOAD TEST

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Cos PV


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INSTRUCTION MANUAL

1.4.1 OBJECTIVES

Calculate the hysteresis losses, measure the no-load current and calculate the no loadPower Factor of single and three phase transformers.


The power absorbed by a transformer with its secondary windings open (no load) iscaused by hysteresis losses and eddy currents.

To reduce the hysteresis losses a ferromagnetic material is used that has a narrowhysteresis loop, while to reduce the eddy currents the magnetic iron core is laminatedand its sheets are insulated by means of special resins.

1.4.3 FORMULAE


Voltage V VoltsCurrent I AmperesInput Power P WattsPower W Watts

Power Factor Cos

Single phase transformers: P = W

I = P/(V * Cos )Cos = P/(V * I)

1.4.4 COMPONENTS

Single Phase Transformer Model A4110Power Supply Model A0240Cables Model A4890Cables Support Model A4891Ammeters (A) With adequate range for this test

Wattmeters (W) With adequate range for this testVoltmeter (V) With adequate range for this test

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INSTRUCTION MANUAL


Theoretical Diagram


Primary Secondary

PS2

Execution Diagram

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W1

V

A


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INSTRUCTION MANUALA0240 Section PS1 Sections PS2 - 3Section PS4

1.4.6 EXECUTION




- Switch on the power supply.Increase the input voltage gradually in 20% steps from 0% to 100% of thetransformer nominal voltage

- At each step measure the voltage, current and power readings and enter them in the

worksheet tables.

- Calculate the no load input power, power factor and no load current with the aboveformulae.

- Plot the graphs

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V mA

A

ACDC

230 V< 24v

0v

220v

0v

160v

0v

110v

220v

g

TransformerDigital Multimeter

Power supply


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INSTRUCTION MANUAL

1.4.7 WORKSHEETS


Input Voltage % 20 40 60 80 100

Winding Voltage V V

Current A A

Wattmeter W W

Power Factor Cos

Transformer Model:

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INSTRUCTION MANUAL

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PI

VTransformer Model:


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INSTRUCTION MANUAL

P 22

I

PI

VTransformer Model:

MBB2083-EXP 1 Transformer

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