AS/NZS 60076.10.1:2023

AS/NZS 60076.10.1:2023 Power transformers Determination of sound levels - Application guide (IEC 60076-10-1:2016 (ED. 2.1) MOD)

CONTENTS

FOREWORD

1 Scope

2 Normative references

3 Basic physics of sound

3.1 Phenomenon

3.2 Sound pressure, p

3.3 Particle velocity, u

3.4 Sound intensity,

3.5 Sound power, W

3.6 Sound fields

3.6.1 General

3.6.2 The free field

3.6.3 The diffuse field

3.6.4 The near-field

3.6.5 The far-field

3.6.6 Standing waves

4 Sources and characteristics of transformer and reactor sound

4.1 General

4.2 Sound sources

4.2.1 Core

4.2.2 Windings

4.2.3 Stray flux control elements

4.2.4 Sound sources in reactors

4.2.5 Effect of current harmonics in transformer and reactor windings

4.2.6 Fan noise

4.2.7 Pump noise

4.2.8 Relative importance of sound sources

4.3 Vibration transmission

4.4 Sound radiation

4.5 Sound field characteristics

5 Measurement principles

5.1 General

5.2 A-weighting

5.3 Sound measurement methods

5.3.1 General

5.3.2 Sound pressure method

5.3.3 Sound intensity method

5.3.4 Selection of appropriate sound measurement method

5.4 Information on frequency bands

5.5 Information on measurement surface

5.6 Information on measurement distance

5.7 Information on measuring procedures (walk-around and point-by-point)

6 Practical aspects of making sound measurements

6.1 General

6.2 Orientation of the test object to avoid the effect of standing waves

6.3 Device handling for good acoustical practice

6.4 Choice of microphone spacer for the sound intensity method

6.5 Measurements with tank mounted sound panels providing incomplete coverage

6.6 Testing of reactors

7 Difference between factory tests and field sound level measurements

7.1 General

7.2 Operating voltage

7.3 Load current

7.4 Load power factor and power flow direction

7.5 Operating temperature

7.6 Harmonics in the load current and in voltage

7.7 DC magnetization

7.8 Effect of remanent flux

7.9 Sound level build-up due to reflections

7.10 Converter transformers with saturable reactors (transductors)

Annex A (informative) Sound level built up due to harmonic currents in windings

A.1 Theoretical derivation of winding forces due to harmonic currents

A.2 Force components for a typical current spectrum caused by a B6 bridge

A.3 Estimation of sound level increase due to harmonic currents by calculation

Bibliography