Vanguard LTCA-10, LTCA-40 User Manual

USER’S MANUAL

for the

LTCA-10™
LTCA-40™

LOAD TAP CHANGER ANALYZER

Vanguard Instruments Company, Inc.

1520 S. Hellman Ave.
Ontario, California 91761

TEL: [phone] October 2011
FAX: [phone] Rev. 2.2

LTCA-10/LTCA-40 USER’S MANUAL

SAFETY SUMMARY

NOTICE

This manual applies to both the LTCA-10 and LTCA-40. The operating procedures are virtually
the same for both models, and any differences are clearly described within the step-by-step
procedures.

FOLLOW EXACT OPERATING PROCEDURES

Any deviation from the procedures described in this User’s Manual may create one or more
safety hazards, may damage the LTCA-10/40, damage the test transformer, or cause errors in the
test results. Vanguard Instruments Company, Inc. assumes no liability for unsafe or improper use
of the LTCA-10/40.

All safety precautions provided in this manual must be observed during all phases of testing
including test preparation, test lead connection, actual testing, and test lead disconnection.

SAFETY WARNING AND CAUTIONS

The LTCA-10/40 shall be used only by trained operators. All transformers under test shall be
off-line and fully isolated.

DO NOT MODIFY TEST EQUIPMENT

To avoid the risk of introducing additional or unknown hazards, do not install substitute parts or
perform any unauthorized modification to any LTCA-10/40 test unit. To ensure that all designed
safety features are maintained, it is highly recommended that repairs be performed only by
Vanguard Instruments Company factory personnel or by an authorized repair service.
Unauthorized modifications can cause safety hazards and will void the manufacturer’s warranty.

WARNING

Do not remove test leads during a test. Failure to heed this warning can result in electrical shock
to personnel and damage to the equipment.

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LTCA-10/LTCA-40 USER’S MANUAL

TABLE OF CONTENTS

CONVENTIONS USED IN THIS DOCUMENT .......................................................................... 5

1.0 INTRODUCTION ............................................................................................................... 6

1.1 General Description .......................................................................................................... 6

1.2 Functional Description ..................................................................................................... 6

1.3 Furnished Accessories ...................................................................................................... 7

2.0 TECHNICAL SPECIFICATIONS ...................................................................................... 8

2.1 LTCA-10 Technical Specifications .................................................................................. 8

2.2 LTCA-40 Technical Specifications .................................................................................. 9

3.0 CONTROLS AND INDICATORS.................................................................................... 10

3.1 LTCA-10 Controls and Indicators .................................................................................. 10

3.2 LTCA-40 Controls and Indicators .................................................................................. 12

4.0 PRE-TEST SETUP ............................................................................................................ 14

4.1 Operating Voltages ......................................................................................................... 14

4.2 LTCA-10/40 LCD Contrast Control .............................................................................. 14

4.3 LTCA-10/40 Printer Paper Control ................................................................................ 14

4.4 LTCA-10/40 Printer Paper ............................................................................................. 14

5.0 OPERATING PROCEDURES .......................................................................................... 15

5.1 Typical Connections to a Load Tap Changer (LTC) ...................................................... 15

5.2 LTCA-10 Cable Connections ......................................................................................... 15

5.3 LTCA-40 Cable Connections ......................................................................................... 16

5.4 General Procedures ........................................................................................................ 19

5.5 Performing a Resistance Test ......................................................................................... 20

5.5.1. Resistance Test Result Printouts ............................................................................. 27

5.6 Performing a Special Resistance Test ............................................................................ 29

5.6.1. Special Resistance Test Result Printout .................................................................. 34

5.7 Performing a Dynamic LTC Test ................................................................................... 35

5.7.1. Dynamic LTC Test Result Printouts ....................................................................... 40

5.8 Diagnostic Mode ............................................................................................................ 42

5.9 Setup Menu .................................................................................................................... 44

5.9.1. Entering the Transformer ID ................................................................................... 44

5.9.2. Restoring a Test Record .......................................................................................... 47

5.9.3. Printing the Test-Record Directory ......................................................................... 50

5.9.4. Erasing a Test Record ............................................................................................. 52

5.9.5. Enabling the Computer Interface ............................................................................ 54

5.9.6. Setting the Date and Time ....................................................................................... 55

5.9.7. Setting the Test Value Display Font ....................................................................... 56

6.0 LTCA-10/40 SPECIAL FEATURES ................................................................................ 57

6.1 Bypassing the Resistance Value Display Delay ............................................................. 57

6.2 Converting Resistance Measurements ........................................................................... 57

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LTCA-10/LTCA-40 USER’S MANUAL

LIST OF FIGURES

Figure 1.0 LTCA-10 Controls and Indicators ............................................................................... 10

Figure 2.0 LTCA-40 Controls and Indicators ............................................................................... 12

Figure 3.0 Typical Connections to a Load Tap Changer (LTC) ................................................... 15

Figure 4.0 Typical LTCA-10 Connection Diagram (Dynamic Resistance Test) ......................... 15

Figure 5.0 Typical LTCA-40 Connection Diagram (Dynamic Resistance Test) ......................... 16

Figure 6.0 Typical LTCA-40 Connection Diagram (2 Windings) ............................................... 17

Figure 7.0 Typical LTCA-40 Connection Diagram (3 Windings) ............................................... 18

Figure 8.0 Typical Triple Reading Test Report Printout .............................................................. 27

Figure 9.0 Typical Dual Reading Test Report Printout ................................................................ 27

Figure 10.0 Typical Single Reading Test Report Printout ............................................................ 28

Figure 11.0 Typical Single Reading Test Report Printout ............................................................ 34

Figure 12.0 Sample Normal Dynamic LTC Test Plot .................................................................. 40

Figure 13.0 Sample Dynamic LTC Test Expansion Plot .............................................................. 41

Figure 14.0 Typical Test Record Printout ..................................................................................... 49

Figure 15.0 Typical Record Directory Printout ............................................................................ 51

LIST OF TABLES

Table 1.0 LTCA-10 Specifications ................................................................................................. 8

Table 2.0 LTCA-40 Specifications ................................................................................................. 9

Table 3.0 Functional Descriptions of LTCA-10 Controls and Indicators .................................... 11

Table 4.0 Functional Descriptions of LTCA-40 Controls and Indicators .................................... 13

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LTCA-10/LTCA-40 USER’S MANUAL

CONVENTIONS USED IN THIS DOCUMENT

This document uses the following conventions:

• A key or switch on the LTCA-10/40 is indicated as [KEY]

•

Menu options are referenced as (MENU OPTION)
Screen and menu names are referenced as “SCREEN/MENU NAME”

•

• LTCA-10/40 LCD screen output is shown as:

1. OPTION 1

2. OPTION 2

3. OPTION 3

• Warning messages are indicated as:

Warning message

WARNING

• Important notes are indicated as:

Note details

NOTE

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LTCA-10/LTCA-40 USER’S MANUAL

1.0 INTRODUCTION

1.1 General Description

The Vanguard LTCA-10 and LTCA-40 are microprocessor-controlled winding resistance meters.
These devices are designed to accurately measure large transformer winding resistance, motor
winding resistance, or the resistance of large inductive devices. This manual addresses the
LTCA-10 and LTCA-40 as one device. Any differences between the LTCA-10 and LTCA-40 are
addressed separately.

The LTCA-10 uses a 60Vdc/10 Amperes Direct Current (DC) power supply while the LTCA-40
uses a 60VDC/40 Amperes DC power supply. Both devices are capable of reading winding
resistances ranging from 1 micro-ohm to 500 ohms. Three voltage sensing channels allow the
LTCA-10/40 to read three resistance values in the same test. To ensure operator safety, the
LTCA-10/40 automatically discharges the stored energy in the transformer at the end of each
test.

The LTCA-10/40 has one resistance reading channel (V1) dedicated for dynamic resistance
testing. The dynamic resistance test feature can be used to monitor the transformer LTC or
Voltage Regulator contact resistance while changing tap positions. A resistance plot shows the
transformer LTC contact and winding resistance and can be used to detect LTC/Voltage
Regulator contact problems.

The transformer LTC or Voltage Regulator AC motor current can also be monitored by the
LTCA-10/40 using an AC clamp on the current sensor. This feature can be used to monitor the
LTC motor “On-Time” at each tap change operation.

The LTCA-10/40 is rugged, portable, and easy to use, requiring little training for first-time users.
A 16-key membrane keypad is used to control the unit. The LTCA-10/40 features a back-lit LCD
screen (64 x 128 dot graphic) that is viewable in bright daylight as well as low-light conditions.
A built-in thermal printer can print results on 4.5-inch wide thermal paper.

The LTCA-10/40 can store 128 static test records (48 tests per record) and 11 dynamic resistance
test records in Flash EEPROM. Test records can be recalled locally or transferred to a PC via the
available interfaces (RS-232C port, USB port, USB Flash drive port). A built-in USB Flash drive
interface provides a convenient method for transferring test records to or from a USB Flash
drive. Test records can also be transferred directly to a PC via the RS-232C or USB interface
ports. If using a USB Flash drive, test records stored in the LTCA-10/40’s internal memory can
be transferred to the drive, and then the supplied PC software can be used to view the test records
stored on the drive. Up to 999 test records can be stored on a USB Flash drive.

1.2 Functional Description

The LTCA-10/40’s operation is based on the electrical relationship described by Ohm’s law:
R=V/I, where I is a known current and V is the DC voltage measured across the unknown
resistance. The value of the unknown resistance is calculated by dividing the measured voltage
by the current which is calculated by the microprocessor. Calculated resistance readings are then
displayed on the unit’s back-lit LCD screen.

A special current source allows the LTCA-10 to output 1, 5 and 10 Amperes of test current. The
LTCA-40 can output 1, 5, 10 or 40 Amperes of test current. For added safety, the current source

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LTCA-10/LTCA-40 USER’S MANUAL

circuit is thermally protected. Also, a built-in discharge circuit automatically discharges the
stored energy in the transformer at the end of each test.

1.3 Furnished Accessories

The LTCA-10/40 is furnished with eight 50-foot test cables with “quick disconnect” type test
plugs on the unit end and battery-type clamps at the test load end. One power cord, one ground
cable, one current sense cable, one LTC operation cable and a cable-carrying bag is also
included.

7

2.0 TECHNICAL SPECIFICATIONS

2.1 LTCA-10 Technical Specifications

Table 1.0 LTCA-10 Specifications

TYPE Load tap changer analyzer

PHYSICAL SPECIFICATIONS 21”W x 9” H x 17”D (53 cm x 24 cm x 43 cm); Weight: 33 lbs (15.4 kg)

OPERATING VOLTAGE 100 – 240 Vac, 50/60 Hz

RESISTANCE READING

RANGE

ACCURACY 1 – 19,999 micro-ohms: ±0.5% reading, ±1 count;

RESISTANCE CHANNELS Three static resistance reading channels, One dynamic resistance channel

TEST VOLTAGE 60 Vdc max

TEST CURRENTS 1 ampere, 5 amperes, 10 amperes

AC CURRENT PROBE Clamp-on current sensor, 1 – 20 Amperes, AEMC model MN106

DISPLAY Back-lit LCD Screen (64 x 128 dot graphic ); viewable in bright sunlight and

PRINTER 4.5-inch wide thermal printer

EXTERNAL DATA STORAGE One USB Flash drive interface port; stores up to 999 test records on a USB

COMPUTER INTERFACES One RS-232C port, One USB port

INTERNAL TEST RECORD

STORAGE

LOAD TAP CHANGER

CONTACT

SAFETY Designed to meet UL 61010A-1 and CAN/CSA C22.2 No. 1010.1-92

ENVIRONMENT Operating: -10˚C to 50˚ C (15˚F to +122˚ F); Storage: -30˚ C to 70˚ C (-

CABLES One 50-foot current cable set, Three 50-foot resistance cable sets, One

OPTIONS Transportation Case

WARRANTY One year on parts and labor

1 micro-ohm – 500 ohms

20 – 999 milli-ohms: ±1% reading, ±1 count;
1 – 500 ohms: ±1.5% reading, ±1 count

low-light levels

Flash drive (not included)

Stores up to 128 static resistance test records (48 tests per record) and 11
dynamic resistance test records

240 Vac, 1A

standards

22˚F to +158˚ F)

ground cable, One USB cable, One RS-232C cable, One current sense
cable, One LTC control cable, power cord, cable bag

LTCA-10/LTCA-40 USER’S MANUAL

NOTE

The above specifications are valid at nominal operating voltage and at a
temperature of 25°C (77°F). Specifications may change without prior notice.

8

2.2 LTCA-40 Technical Specifications

Table 2.0 LTCA-40 Specifications

TYPE Load tap changer analyzer

PHYSICAL SPECIFICATIONS 25”W x 8.5”H x 20”D (63.5 cm x 21.6 cm x 50 cm); Weight: 46 lbs (20 kg)

OPERATING VOLTAGE 100 – 240 Vac, 50/60 Hz

RESISTANCE READING

RANGE

ACCURACY 1 – 19,999 micro-ohms: ±0.5% reading, ±1 count;

RESISTANCE CHANNELS Three static resistance reading channels, One dynamic resistance channel

TEST VOLTAGE 60 Vdc max

TEST CURRENTS 1 ampere, 5 amperes, 10 amperes, 40 amperes

AC CURRENT PROBE Clamp-on current sensor, 1 – 20 Amperes, AEMC model MN106

DISPLAY Back-lit LCD Screen (64 x 128 dot graphic ); viewable in bright sunlight and

PRINTER 4.5-inch wide thermal printer

EXTERNAL DATA STORAGE One USB Flash drive interface port; stores up to 999 test records on a USB

COMPUTER INTERFACES One RS-232C port, One USB port

INTERNAL TEST RECORD

STORAGE

LOAD TAP CHANGER

CONTACT

SAFETY Designed to meet UL 61010A-1 and CAN/CSA C22.2 No. 1010.1-92

ENVIRONMENT Operating: -10˚C to 50˚ C (15˚F to +122˚ F); Storage: -30˚ C to 70˚ C (-22˚F

CABLES One 50-foot current cable set, Three 50-foot resistance cable sets, One

OPTIONS Transportation Case

WARRANTY One year on parts and labor

1 micro-ohm – 500 ohms

20 – 999 milli-ohms: ±1% reading, ±1 count;
1 – 500 ohms: ±1.5% reading, ±1 count

low-light levels

Flash drive (not included)

Stores up to 128 static resistance test records (48 tests per record) and 11
dynamic resistance test records

240 Vac, 1A

standards

to +158˚ F)

ground cable, One USB cable, One RS-232C cable, One current sense
cable, One LTC control cable, power cord, cable bag

LTCA-10/LTCA-40 USER’S MANUAL

The above specifications are valid at nominal operating voltage and at a
temperature of 25°C (77°F). Specifications may change without prior notice.

NOTE

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LTCA-10/LTCA-40 USER’S MANUAL

3.0 CONTROLS AND INDICATORS

3.1 LTCA-10 Controls and Indicators

The LTCA-10’s controls and indicators are shown in Figure 1.0 below. A leader line with an
index number points to each control and indicator, which is cross-referenced to a functional
description in Table 3.0. The table describes the function of each item on the control-panel. The
purpose of the controls and indicators may seem obvious, but users should become familiar with
them before using the LTCA-10/40. Accidental misuse of the controls will usually cause no
serious harm. Users should also be familiar with the safety summary found on the front page of
this User’s Manual.

Figure 1.0 LTCA-10 Controls and Indicators

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LTCA-10/LTCA-40 USER’S MANUAL

Table 3.0 Functional Descriptions of LTCA-10 Controls and Indicators

Item

Number

1
2
3
4

5

6

7

8

9

10

11

12

13

14
15

16
17

Panel Markings Functional Description

AC Current Clamp-on AC current probe connector

USB USB Interface Port

Flash Drive USB Flash Drive Interface Port

None Air Vents

120-240 7.5A, 50-60

Hz

Fuse: 250Vac, 1A

Fast-Blow

GROUND

None

None

LTC Control

DISCHARGE

HIGH VOLTAGE

PRESENT

None

RS-232C

V1, V2, V3,

CURRENT (I+, I-)

RAISE Fuse for the LTC Control Raise leads

LOWER Fuse for the LTC Control Lower leads

LTC CONTROL Load Tap Changer controller connector

Input power connector with third-wire safety ground, ON/OFF rocker toggle
switch with built-in fuse protection

5/16-18 threaded stud, with hand-turned wing nut, safety ground. This must be
connected to station ground before connecting LCTA-10 test leads to the
transformer

Built in 4.5-inch wide thermal printer.
NOTE: For best printing results, it is recommended that only VIC thermal
paper be used

Liquid-Crystal Display, 64 x 128 dot graphic display. Back-lit and viewable in
bright sunlight and low-light conditions. Displays menus, user selections,
status readouts and test results

Load Tap Changer Control. Allows the user to change the Load Tap Changer
position using the RAISE and LOWER buttons

Red LED indicator light. When lit, this indicator warns the operator that the
LTCA-10 is discharging the stored energy in the transformer.

Do not disconnect test leads when this light is on. Failure to heed this
warning can result in shock to personnel

Red LED indicator light. Lights to warn operator that there is a possibility that
voltage exists across test leads.

Do not disconnect test leads when this light is on. Failure to heed this
warning can result in shock to personnel

Membrane keypad, 10 alpha-numeric keys and 6 function keys (START,
STOP, CLEAR, ENTER, and CONTRAST/PAPER positioning UP and DOWN)

9-pin RS-232C interface port; female DB type. Data rate is set to 19,200 baud,
1 start bit, 2 stop bits, 8 data bits and no parity bit

Pin Signal

2 RX
3 TX
5 Signal Ground

Voltage sensing input channels 1, 2, and 3. Female test connector jacks for
connecting test current output test leads

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LTCA-10/LTCA-40 USER’S MANUAL

3.2 LTCA-40 Controls and Indicators

The LTCA-40’s controls and indicators are shown in Figure 2.0 below. A leader line with an
index number points to each control and indicator, which is cross-referenced to a functional
description in Table 4.0. The table describes the function of each item on the control-panel. The
purpose of the controls and indicators may seem obvious, but users should become familiar with
them before using the LTCA-10/40. Accidental misuse of the controls will usually cause no
serious harm. Users should also be familiar with the safety summary found on the front page of
this User’s Manual.

Figure 2.0 LTCA-40 Controls and Indicators

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LTCA-10/LTCA-40 USER’S MANUAL

Table 4.0 Functional Descriptions of LTCA-40 Controls and Indicators

Item

Number

1
2

3

4

5

6

7

8

9

10

11

12

13

14
15

16
17

Panel Markings Functional Description

AC Current Clamp-on AC current probe connector

USB USB Interface port

None

120-240 7.5A, 50-60

Hz

Fuse: 250Vac, 1A

Fast-Blow

GROUND

Flash Drive USB Flash Drive Interface Port

None

None

LTC Control

DISCHARGE

HIGH VOLTAGE

PRESENT

None

RS-232C

V1, V2, V3,

CURRENT (I+, I-)

RAISE Fuse for LTC Control Raise leads

LOWER Fuse for LTC Control Lower leads

LTC CONTROL Load Tap Changer controller connector

The air intake cooling fans maintain the internal temperature. There are output
air fans on the sides of the case

Input power connector with third-wire safety ground, ON/OFF rocker toggle
switch with built-in fuse protection

5/16-18 threaded stud, with hand-turned wing nut, safety ground. This must be
connected to station ground before connecting LCTA-40 test leads to the
transformer

Built in 4.5-inch wide thermal printer.
NOTE: For best printing results, it is recommended that only VIC thermal paper
be used

Liquid-Crystal Display, 64 x 128 dot graphic display. Back-lit and viewable in
bright sunlight and low-light conditions. Displays menus, user selections, status
readouts and test results

Load Tap Changer Control. Allows the user to change the Load Tap Changer
position using the RAISE and LOWER buttons

Red LED indicator light. When lit, this indicator warns the operator that the
LTCA-40 is discharging the stored energy in the transformer.

Do not disconnect test leads when this light is on. Failure to heed this
warning can result in shock to personnel

Red LED indicator light. Lights to warn operator that there is a possibility that
voltage exists across test leads.

Do not disconnect test leads when this light is on. Failure to heed this
warning can result in shock to personnel

Membrane keypad, 10 alpha-numeric keys and 6 function keys (START, ST OP,
CLEAR, ENTER, and CONTRAST/PAPER positioning UP and DOWN)

9-pin RS-232C interface port; female DB type. Data rate is set to 19,200 baud,
1 start bit, 2 stop bits, 8 data bits and no parity bit

Pin Signal

2 RX
3 TX
5 Signal Ground

Voltage sensing input channels 1, 2, & 3. Female test connector jacks for
connecting test current output test leads

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LTCA-10/LTCA-40 USER’S MANUAL

4.0 PRE-TEST SETUP

4.1 Operating Voltages

The LTCA-10/40’s operating voltages are 100-240 Vac and 50/60 Hz.

4.2 LTCA-10/40 LCD Contrast Control

To increase the LCD screen contrast, press and hold the [PAPER ∧ Contrast] key for two
seconds.

To decrease the LCD screen contrast, press and hold the [PAPER ∨ Contrast] key for two
seconds.

4.3 LTCA-10/40 Printer Paper Control

To advance the LTCA-10/40 printer paper, press and release the
To retract the LTCA-10/40 printer paper, press and release the

[PAPER ∧ Contrast] key.

[PAPER ∨ Contrast] key.

4.4 LTCA-10/40 Printer Paper

The LTCA-10/40’s built-in thermal printer uses 4.5-inch wide thermal paper for printing test
results. To maintain the highest print quality and to avoid paper jams, the use of thermal paper
supplied by Vanguard Instruments Company is highly recommended. Additional paper can be
ordered from the following sources:

Vanguard Instruments Co, Inc.

1520 S. Hellman Avenue
Ontario, CA 91761
Tel: [phone]
Fax: [phone]
Part Number: VIC TP-4 paper

BG Instrument Co.

13607 E. Trent Avenue
Spokane, WA 99216
Tel: [phone]
Fax: [phone]
Part Number: VIC TP-4 paper

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LTCA-10/LTCA-40 USER’S MANUAL

5.0 OPERATING PROCEDURES

The LTCA-10/40 is simple to operate and only requires the selection of choices from display
menus and responding to displayed prompts. However, first-time operators should review the
following operating procedures to become familiar with all LTCA-10/40 operations and the
logical branching for various test options. More experienced operators may use these procedures
as a handy help and reference guide.

5.1 Typical Connections to a Load Tap Changer (LTC)

Figure 3.0 Typical Connections to a Load Tap Changer (LTC)

5.2 LTCA-10 Cable Connections

Do not touch or disconnect any test lead that is connected to a transformer
terminal while high current is being conducted during a test. Failure to heed this
warning can result in electrical shock to personnel and/or damage to the

WARNING

equipment.

Figure 4.0 Typical LTCA-10 Connection Diagram (Dynamic Resistance Test)

WARNING

After discharge, always disconnect test clips slowly from transformer bushings
to prevent an accidental flash-over.

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LTCA-10/LTCA-40 USER’S MANUAL

5.3 LTCA-40 Cable Connections

Typical connection diagrams of the LTCA-40 are shown in Figure 4.0, 5.0, and 6.0.

Do not touch or disconnect any test lead that is connected to a transformer
terminal while high current is being conducted during a test. Failure to heed this
warning can result in electrical shock to personnel and/or damage to the

WARNING

equipment.

WARNING

Figure 5.0 Typical LTCA-40 Connection Diagram (Dynamic Resistance Test)

After discharge, always disconnect test clips slowly from transformer bushings to
prevent any accidental flash-over.

16

LTCA-10/LTCA-40 USER’S MANUAL

Figure 6.0 Typical LTCA-40 Connection Diagram (2 Windings)

17

LTCA-10/LTCA-40 USER’S MANUAL

Figure 7.0 Typical LTCA-40 Connection Diagram (3 Windings)

18