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086-627
Name

The Voltech Handbook of Transformer Testing

Description
This article covers a wide range of transformer theory and Voltech's testing capability.
The Voltech Handbook of Transformer Testing
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Expand 1 Transformer Basics1 Transformer Basics
Collapse 2 Available Tests2 Available Tests
2.1 CTY - Continuity
2.2 R - Winding Resistance
2.3 RLS or RLP - Equivalent Series or Parallel R
2.4 LS_LP - Primary Inductance
2.5 LSB_LPB - Inductance With Bias Current
2.6 QL - Q factor
2.7 D - Dissipation Factor
2.8 LL - Leakage Inductance
2.9 C - Inter-winding Capacitance
2.10 TR - Turns Ratio and Phasing
2.11 TRL - Turns Ratio by Inductance
2.12 Z_ZB - Impedance_Impedance with Bias
2.13 R2 - DC Resistance Match
2.14 L2 - Inductance Match
2.15 C2 - Capacitance Match
2.16 GBAL - General Longitudinal Balance
2.17 LBAL - Longitudinal Balance
2.18 ILOS - Insertion Loss
2.19 RESP - Frequency Response
2.20 RLOS - Return Loss
2.21 ANGL - Impedance Phase Angle
2.22 PHAS - Inter-winding Phase Test
2.23 TRIM - Trimming Adjustment
2.24 OUT - Output To User Port
2.25 IR - Insulation Resistance
2.26 HPDC - DC HI-POT
2.27 HPAC - AC HI-POT
2.28 SURG - Surge Stress Test
2.29 STRW - Stress Watts
2.30 MAGI - Magnetizing Current
2.31 VOC - Open Circuit Voltage
2.32 WATX - Wattage (External Source)
2.33 STRX - Stress Watts (External Source)
2.34 MAGX - Magnetizing Current (Ext. Source)
2.35 VOCX - O.C. Voltage (External Source)
2.36 LVOC - Low Voltage Open Circuit
2.37 ILK - Leakage Current
2.38 LSBX - Inductance with External Bias (Series)
2.39 LPBX - Inductance with External Bias (Parallel)
2.40 ZBX - Impedance with External Bias
2.41 ACRT - AC HI-POT Ramp
2.42 DCAT - DC HI-POT Ramp
2.43 ACVB - AC Voltage Break Down
2.44 DCVB - DC Voltage Break Down
2.45 WATT - Wattage
2.0 Available Tests On The AT Series
Expand 3 Examples of Different Transformer Types3 Examples of Different Transformer Types

2. Available Tests, Where Used and Measurement Conditions.

2.0 Available Tests On The AT Series

The following table summarizes the tests available for the AT and indicates where they might be used: -

LSBX, LPBX and ZBX require the use of one or more Voltech DC1000 Precision DC Bias Current Sources. Contact your Voltech sales office for details.

1. LV Tests





TEST

DESCRIPTION

Main Application

Winding Tested

Reason for Test

CTY

Continuity

All transformers

All windings

Properly installed fixture

R

DC Resistance

All transformers

All windings

Properly installed fixture. Correct wire used. Integrity of terminations

LS

Inductance (Series circuit)

Most transformers, but usually not line frequency transformers

One winding, usually the primary

Correct primary turns. Right grade of core material. Core correctly assembled

LP

Inductance (Parallel circuit)

Most transformers, but usually not line frequency transformers

One winding, usually the primary

Correct primary turns. Right grade of core material. Core correctly assembled

QL

Quality Factor

Most transformers, but usually not line frequency transformers

One winding, usually the primary

Right grade of core material. Core correctly assembled. Check for shorted turns

RLS

Equivalent Series Resistance

Most transformers, but usually not line frequency transformers

One winding, usually the primary

Right grade of core material. Core correctly assembled. Check for shorted turns

RLP

Equivalent Parallel Resistance

Most transformers, but usually not line frequency transformers

One winding, usually the primary

Right grade of core material. Core correctly assembled. Check for shorted turns

D

Dissipation Factor

Most transformers, but usually not line frequency transformers

One winding, usually the primary

Right grade of core material. Core correctly assembled. Check for shorted turns

LL

Leakage Inductance

SMPS transformers Communication Transformers Others as applicable

Selected windings

Check windings have been installed in the correct position relative to the core

C

Interwinding Capacitance

High frequency transformers. Isolating transformers

Selected windings

Check winding positioning. Check insulation thickness between windings

TR

Turns Ratio and Phasing

Most transformers, but usually not line frequency transformers

All windings

Check windings have correct turns and phasing

TRL

Turns Ratio by Inductance

As with Turns Ratio but used where there is poor flux linkage between windings.

All windings

Check windings have correct turns and phasing

LVOC

Low Voltage Open Circuit

Usually line frequency transformers

All other windings

Correct secondary turns. Correct phasing

IR

Insulation Resistance

All transformers

Between selected windings

Winding isolation check where safety is not involved

LSB

Inductance with Bias Current (Series Circuit)

Transformers for use in applications where passing significant (dc) bias current is part of the normal operation

One winding

Correct number of turns. Right grade of core material. Core correctly assembled.

LPB

Inductance with Bias Current (Parallel Circuit)

Transformers for use in applications where passing significant (dc) bias current is part of the normal operation

One winding

Correct number of turns. Right grade of core material. Core correctly assembled.

OUT

Output To User Port

n/a

n/a

Allows the AT to perform external switching as part of the test program.

R2

DC Resistance Match

SMPS, audio & telecom

All windings

Checks matching between windings

L2

Inductance Match

SMPS, audio & telecom transformers

All windings

Checks matching between windings

C2

Capacitance Match

SMPS, audio & telecom transformers

All Windings

Checks correct winding position on bobbin

GBAL

General Longitudinal Balance

Audio & telecom transformers

Selected Windings

Checks common mode rejection ratio

LBAL

Longitudinal Balance

Audio & telecom transformers

Selected Windings

Checks common mode rejection ratio

ILOS

Insertion Loss

Audio & telecom transformers

Selected Windings

Checks losses within the transformer

RESP

Frequency Response

Audio & telecom transformers

Selected Windings

Checks losses over a range of frequencies

RLOS

Return Loss

Audio & telecom transformers

Selected Windings

Checks losses returned by a transformer

Z

Impedance

Audio & telecom transformers

Selected Windings

Checks impedance at a given frequency

ZB

Impedance + bias

Audio & telecom transformers

Selected Windings

Checks impedance at a given frequency

ANGL

Impedance Phase Angle

Audio & telecom transformers

Selected Windings

Finds phase shift between Voltage and Current on a winding.

PHAS

Interwinding Phase Test

Audio & telecom transformers

Selected Windings

Measures phase shift between a pair of windings


2.HV Tests





TEST

DESCRIPTION

Main Application

Winding Tested

Reason for Test

HPDC

Hi-Pot (DC)

All transformers especially those used for safety insulation

Between selected windings usually primary to secondary, screens and core

High voltage safety insulation

HPAC

Hi-Pot (AC)

All transformers especially those used for safety insulation

Between selected windings usually primary to secondary, screens and core

High voltage safety insulation

ACRT

Hi-Pot Ramp (AC)

All transformers especially those used for safety insulation

Between selected windings usually primary to secondary, screens and core

High voltage safety insulation

DCRT

Hi-Pot Ramp (DC)

All transformers especially those used for safety insulation

Between selected windings usually primary to secondary, screens and core

High voltage safety insulation

ACVB

Voltage Breakdown (AC)

Transformers with MOV fitted

Between selected windings usually primary to secondary, screens and core

High voltage safety insulation

DCVB

Voltage Breakdown (DC)

Transformers with MOV fitted

Between selected windings usually primary to secondary, screens and core

High voltage safety insulation

WATT

Wattage

50Hz Iron core transformers

One winding

Correct core material. Properly assembled

ILK

Leakage Current Test

Medical applications

Between Primary and Secondary Windings

Checks for a common mode current due to capacitance

STRW

Stress Wattage

Line frequency & High Frequency Transformers

One Winding (Usually the primary)

Checks integrity of inter-turn insulation, the magnetic material and joints

SURG

Surge Stress Test

All transformers, especially those using fine wire

Selected windings

To identify shorted turns

MAGI

Magnetising Current

Usually line frequency transformers

One winding, usually the primary

Correct primary turns Correct core material properly assembled

VOC

Open Circuit Voltage

Usually line frequency transformers

All other windings

Correct secondary turns. Correct phasing


3. DC1000





TEST

DESCRIPTION

Main Application

Winding Tested

Reason for Test

LSBX

Inductance with External Bias (Series Circuit)

Wound components that usually carry a significant DC Bias current in normal operation.

Selected Windings

Checks number of turns, right grade of correctly assembled core material, where bias current is greater than LSB test can handle.

LSBX

Inductance with External Bias (Parallel Circuit)

Wound components that usually carry a significant DC Bias current in normal operation.

Selected Windings

Checks number of turns, right grade of correctly assembled core material, where bias current is greater than LPB test can handle.

ZBX

Impedance with External Bias

Audio & Telecom

Selected Windings

Checks impedance at a given frequency, while applying a greater bias current than is possible with ZB test.

4. AC I/F





TEST

DESCRIPTION

Main Application

Winding Tested

Reason for Test

MAGX

MAGI (External Source)

Usually line frequency transformers

One winding, usually the primary

Correct primary turns. Correct core material properly assembled.

VOCX

VOCX (External Source)

Usually line frequency transformers

All other windings

Correct secondary turns. Correct phasing.

WATX

WATT (External Source)

50Hz Iron core transformers

One winding

Correct core material. Properly assembled.

STRX

STRW (External Source)

Line frequency & High Frequency Transformers

One Winding (Usually the primary)

Checks integrity of inter-turn insulation, the magnetic material and joints.

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