Elgar 251b User manual

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ELGAR TWO-YEAR WARRANTY

Elgar Electronics Corporation (hereinafter referred to as Elgar) warrants its products to be free from defects

in

material and workmanship. This warranty is effective for two years from the date

of

shipment

of

the

product to the original purchaser. Liability

of

Elgar

under

this warranty shall exist provided that:

the Buyer exposes the product to normal use and service and provides normal maintenance

on

the

product;

Elgar is promptly notified

of

defects by the Buyer and that notification occurs within the warranty period;

the Buyer receives a Return Material Authorization {RMA) numberfrom Elgar's Repair Department prior to

the return

of

the product to Elgar for repair, phone 800-73-ELGAR (800-733-5427), ext. 2295;

the Buyer returns the defective product

in

the original,

or

equivalent, shipping container;

if,

upon examination

of

such product by Elgar it is disclosed that,

in

fact, a defect

in

materials and/or

workmanship does exist, that the defect

in

the product was not caused by improper conditions, misuse,

or

negligence; and,

that Elgar QA seal and nameplates have not been altered

or

removed and the equipment has not been

repaired or modified by anyone other than Elgar authorized personnel.

This warranty is exclusive and

in

lieu

of

all other warranties, expressed

or

implied, including, but not limited

to, implied warranties

of

merchantability and fitness

of

the product to a particular purpose. Elgar, its agents,

or

representatives shall in no circumstance be liable

for

any direct, indirect, special, penal,

or

consequential

loss

or

damage

of

any nature resulting from the malfunction

of

the product. Remedies under this warranty

are expressly limited to repair

or

replacement

of

the product.

CONDITIONS

OF

WARRANTY

To

return a defective product, contact an Elgar representative or the Elgar factory for

an

RMA

number.

Unauthorized returns will not be accepted and will be returned at the shipper's expense.

For Elgar products found to be defective within thirty days

of

receipt by the original purchaser, Elgar will

absorb all ground freight charges for the repair. Products found defective within the warranty period, but

beyond the initial thirty-day period, should be returned prepaid to Elgarfor repair. Elgar will repair the unit

and return it by ground freight pre-paid.

Normal warranty service is performed at Elgar during the weekday hours

of

7:30am

to 4:30 pm Pacific

time. Warranty repair work requested to be accomplished outside

of

normal working hours will be subject to

Elgar non-warranty service rates.

Warranty field service is available

on

an emergency basis. Travel expenses (travel time, perdiem expense,

and related air fare) are the responsibility

of

the Buyer. A Buyer purchase order is required by Elgar prior to

scheduling.

A returned product found, upon inspection by Elgar, to be

in

specification is subject to an inspection fee and

applicable freight charges.

Equipment purchased

in

the United States carries only a United States warranty for which repair must be

accomplished at the Elgar factory.

Committed

to

Quality...Striving for Excellence

1.1

1.3

1.9

1.14

1.16

2.1

2.3

2.5

2.8

2.17

3.1

3.3

4.1

4.6

4.8

5.1

5.3

5.5

5.7

5.9

5.12

5.14

TABLE

OF CONTENTS

SECTION I

GENERAL DESCRIPTION

Introduction . . .

General

Description .

Physical Description

Performance Specifications .

System Applications . . .

SECTION II

INSTALLATION

Introduction . . . . . . . .

Unpacking

and

Receiving Inspection

Rack Mounting

Installation

Checkout. . .

Introduction . . . .

Controls

and

Indicators

SECTION

Ill

OPERATION

SECTION

IV

THEORY OF OPERATION

Circuit Description . . . . . . . . . .

Power Supplies . . . . . . . . . . .

Interconnections

for

Multi-Phase Operation

Introduction .

Factory Repair

Test Points . .

Output Regulation Adjustment

Current

Limit

Adjustment

Periodic Maintenance

Troubleshooting . . . .

SECTION V

MAl

NTENANCE

iii

·,

1-1

1-2

2-1

2-2

2-3

3-1

4-1

4-3

5~1

5-1

5-2

6.1

6.3

7.1

7.3

1-1

3-1

1-1

1-2

2-l

2-.2

3-1

4-1

4-2

4-3

4-4

4-5

5-1

5-2

5-3

5-4

7-1

7-2

7-3

7-4

TABLE

OF

CONTENTS (Continued)

·

Introduction

Spare Parts .

Introduction

Diagrams . .

Performance Specifications .

Controls and Indicators . .

SECTION

VI

PARTS

LIST

SECTION

VII

DIAGRAMS

LIST

OF

TABLES

LIST

OF

ILLUSTRATIONS

Power

Output

Derating . . . . . . . . .

Typical Harmonic

Distortion

at Rated Power . •

Model

251

B Rear

View

. . .

Model

501

B Rear

View

. . . . . .

Front

View

Model 251 B, 501 B . . .

Model 251

Band

501 B Block Diagram .

Output

Configurations . . . . . .

Vector

Diagram . . . . . . . . .

Super Stable, Quasi-Square

Wave

Interconnections .

Signal Routing Plug-In Connections

Model 251 B

Top

View

Model

251

B

Bottom

View

Model

501

B

Top

View

Model

501

B

Bottom

View

Model

2518

Interconnect Diagram, 6201000-01 .

Model

251

B/Model 501 B

Amplifier

Board, Schematic 6200001 .

Modei251B/Model

501B

Amplivier

Board, Assembly Dwg.

5200001-01,-02.

Model

5018

Interconnect Diagram, 6051001-01

...........

.

iv

6-1

7-1/7-2

1-4

3-1

1-5

2-4

3-2

4-2

4-4

4-5

4-7

4-8

5-3

5-4

5-5

5-6

7-3/7-4

7-5/7-6

7-7/7-8

. 7-9/7-10

·1.1

INTRODUCTION

SECTION I

GENERAL DESCRIPTION

1.

2

This

manual

has

been

prepared

for

use

with

the

Elgar

Model 2518

and

5018 Power

Sources.

The

information

it

contains

is

intended

for

use

by

operators

and

trained

technicians.

The

manual

provides

information

regarding

the

installation,

theory

of

operation

and

maintenance

of

the

AC

Power

Source.

Also

included

is a

parts

list

and

schematic

diagrams

to

aid

in

maintaining

the

unit

at

optimum

performance.

1.3

GENERAL DESCRIPTION

1.4

The

Elgar

Model 2518

and

501

B Power

Sources

provides

AC

power

at

precise

frequencies

for

testing,

motor

operation,

and

frequency

conversion.

1.

5

The

basic

power

amplifier

consists

of

two

DC

power

supplies

and

a

direct-

coupled

amplifier

driving

a

tapped

output

transformer.

The

output

transformer

of

the

Model 2518

provides

nominal

output

voltages

of

28,

115,

and

230

VAC,

that

are

adjustable

between

0-32,

0-130,

and

0~260

VAC.

The

total

available

power

for

the

Model 2518 is 250VA

at

the

rated

output

voltages.

The

output

transformer

of

the

Model

5018

provides

nominal

output

voltages

of

60,

115

and

230

VAC,

that

are

adjustable

between

0-65,

0-130,

and

0-260 VAC.

The

total

available

power

for

the

Model 5018

is

SOOVA

at

the

rated

output

voltages.

1.6

·Power

at

less

than

full-rated

output

voltage

is

derated

as

shown

in

Figure

1-1.

Figure

1-2

shows

a

typical

harmonic

distortion

curve

over

the

frequency

range

of

both

units.

The

input

power

for

both

units

is

115

or

230

VAC

±10%,

47-53Hz,

10.

1.7

Output

power

frequency

is

established

by·

a

plug-in

oscillator

module.

Output

frequency

range

of

the

Model 2518

at

full

power

is

45

Hz

to

5kHz

and

at

rated

half

power

is

5kHz

to

1OkHz.

The

output

frequency

range

of

the

Model

5018

at

full

power

is

45

Hz

to

5

kHz.

A

variety

of

fixed

and

variable

frequency

plug-in

oscillator

modut·es

are

available

with

frequency

tolerances

up

to

.0001%.

(Refer

to

the

specific

oscillator

manual.)

1.8

The

basic

power

source

output

is

single

phase.

Multi-phase

power

can

be

obtained,

however,

by

stacking

two

or

three

power

sources,

all

driven

by

a

multi-phase

plug-in

oscillator

module.

1-1

1.9

PHYSICAL

DESCRIPTION

1.10

The

Elgar

Model

251

B

is

contained

in

an

all

aluminum

enclosure

designed

with

a

standard

19-inch

rack-mounting

and

slide-out

capability.

Refer

to

para-

graph

2-4,

Section

II

for

mounting

instructions.

The

front

panel

of

the

Model

251

B

contains

a

voltm.eter,

a

voltage

amplitude

control,

a

power

circuit

breaker

and

indicator

light.

The

Elgar

Model

501

B

is

contained

in

an

enclosure

that

consists

of

aluminum

interior

metal

and

a steel

chassis.

The

front

panel

material

is

aluminum.

This

enclosure

is

also

designed

with

a

standard

19

inch

rack

mounting

and

slide

out

capability.

The

front

panel

of

the

Model

501

B

contains

a

voltmeter,

a

voltage

amplitude

control,

a

power

circuit

breaker

and

indicator

light.

1.11

The

wind

tunnel

contains

the

output

power

heatsink

assemblies,

which

comprise

a

two-section

power

amplifier.

The

voltage

amplifier

and

control

circuitry

is

contained

on a

snap-in

circuit

board

with

test

points

and

adjust-

ment

controls

available

at

the

top

of

the

board.

Output

power

of

Model

251

B.

is

available

for

all

output

ranges

at

the

output

power

terminal

block

located

on

the

rear

of

the

chassis.

Output

power

of

the

Model

251

B

is

also

available

at

the

red

and

white

binding

posts

.on

the

front

panel

for

the

0-130

VAC

range

only.

Output

power

for

the

Model

501

B

is

available

for

all

output

ranges

at

the

output

power

terminal

block

located

on

the

rear

of

the

chassis

and

the

red

and

white

binding

posts

on

the

front

panel.

The

0-65VAC

range

on

the

Model

501

B

requires

internal

.jumpering

on

TB2

located

inside

the

unit

on

the

upper

right

side

of

the

chassis.

(Refer

to

schematic

#6051

001).

1.12

The

Elgar

Plug.;...

In

Oscillator

module

(supplied

separately)

mounts

in

the

blank

space

located

on

the

front

panel

of

the

power

source.

In

most

cases,

however,

the

power

source

will

already

be

equipped

with

this

module

depending

on

the

original

purchase

order.

If

removal

of

the

oscillator

assembly

is

necessary,

the

two

thumb

screws

will

facilitate

its

removal

or

installation.

1.13

The

grill

openings

located

on

the

front

panel

and

rear

panel

provide

the

fan

with

the

necessary

air

intake

and

outlet

locations

for

proper

operation.

The

air

is

drawn

into

the

front

grill

and

exhausted

through

the

rear

grill.

CAUTION

Under

no

circumstances

should

the

front

or

rear

grill

openings

be

blocked

or

serious

damage

to

the

power

source

may

occur,

1.14

PERFORMANCE

SPECIFICATIONS

1.15

The

performance

specifications

for

the

Model

251

B

and

Model

501

B

appear

in

Table

1-1;

A

graph

illustrating

output

power

derating

appears

in

Figure

1-1,

while

still

another

graph

illustrating

the

typical

harmonic

distortion

of

the

power

sources

at

rated

power

appears

in

Figure

1-2.

1.16

SYSTEM

APPLICATIONS

1.17

The

Model

251

B

and

501

B can be

connected

in

two's

or

three's

with

a

common

oscillator

to

provide

double

power,

single-phase,

two-phase

and

three-phase

power.

The

various

standard

system

model

numbers

available

are

as

follows:

1-2

1-18

Model

2518

Systems

1.

System

500-1

This

system

consists

of

(2)

Model

251

B's,

(1) Model 400BT

Signal-

Routing

Plug-In

and

(1)

interconnecting

cable.

Not

included

with

the

system

but

necessary

to

complete

it,

is

(1)

400(T)

plug-in

oscillator.

This

system

provides

500VA

single

phase,·

output

power,

at

65VAC,

130VAC,

or

260VAC

output

voltage.

2.

System

500-2

This

system

consists

of

(2)

Model

251

B's

(1)

4008

Signal-Routing

Plug-In,

and

(

1)

interconnecting

cable.

Not

included

with

the

system,

but

necessary

to

complete

it,

is

{1)

Elgar

2-phase

plug-in

oscillator.

This

system

provides

250VA

output

power

per

phase

at

32VAC,

130VAC

or

260VAC

output

voltage.

3.

System

500-30

This

system

consists

of

(2)

Model

251

B's

(

1)

Model

4008

Signal-

Routing

Plug-In,

and

(1)

interconnecting

cable.

Not

included

with

the

system

but

necessary

to

complete

it,

is

(1)

Elgar

3-phase

plug-in

oscillator.

This

system

is

connected

in

a

3-phase,

open-delta

configuration.

The

output

power

per

phase

is

166

VA

at

32

VAC,

130V

AC

or

260VAC

output

voltage.

4.

System

500-3Y

This

system

consists

of

{2)

Model

251

B's

(1)

Model 4008

Signal-

Routing

Plug-In,

and

(1)

interconnecting

cable.

Not

provided

with

the

system,

but

necessary

to

complete

it

is

(2)

Elgar

3-phase

plug-in

oscillator.

This

system

is

connected

in

a

3-phase,

phantom-wye

configuration.

The

output

power

per

phase

is

166VA

at

32VAC,130VAC

or

260VAC

output

voltage.

5.

System

750-3

This

system

consists

of

(3)

Model

251

B's

(1)

Model

4008,

(1)

Model

400C,

and

(1)

interconnecting

cable.

Not

provided

with

the

system,

but

necessary

to

complete

it

is

(1)

Elgar

3-phase

plug-in

oscillator.

This

system

is

connected

in

a

three

amplifier,

3-phase,

wye

configuration.

The

output

power

is

2SOVA

per

phase

at

32VAC,

l30VAC

or

260VAC

output

voltage.

1

...:19

Model

501

B

Systems

1.

System

1000-1

This

system

consists

of

(2)

Model

501

B's

(1)

Model 400BT

Signal-Routing

Plug

in,

and

{1)

interconnecting

cable.

Not

included

with

the

system,

but

necessary

to

complete

it,

is

(1)

400(T)

plug-in

oscillator.

This

system

requires

the

two

power

sources

be

connected

'in

tandem

thus

providing

1000VA

(1

KVA)

single-phase

output

power

at

130V

AC

or

260

VAC

output

voltage.

2.

System

1000-2

This

system

consists

of

(2)

Model

501B's

(1)

Model

400V,

and

(1}

interconnecting

cable.

Not

included

with

the

system,

but

necessary

to

complete

it,

is

(1)

Elgar

2-phase

plug-in

oscillator

•.

This

system

provides

500

VA

power

output

per

phase

at

65

VAC,

130

VAC

or

260

VAC

output

voltage.

1-3

3.

System

1000-3D

This

system

consists

of

(2)

Model

501

B's

(1)

Model

400V,

and

(1)

interconnecting

cable.

Not

included

with

the

system,

but

necessary

to

complete

it,

is

(1)

Elgar

3-phase

plug-in

oscillator.

This

system

is

connected

in

a

3-phase

open-delta

configuration.

The

output

power

per

phase

is

333

VA

at

65

VAC

I

130

VAC

or

260

VAC

output

voltages.

4.

System

1

ooo.;..3Y

This

system

consists

of

(2)

Model

501B's,

(1)

Modei400V

Signal-Routing

Plug-In,

and

(1)

interconnecting

cable.

Not

included

I

but

necessary

to

complete

the

system,

is

(

1)

Elgar

3,-phase

plug-in

osciIIa

tor.

The

system

is

connected

in

a

3-phase,

phantom-wye

configuration

and

has

333

VA

power

output

per

phase

at

65VAC,

130VAC

or

260VAC

output

voltage.

5.

System

1500-3

This

system

consists

of(#)

Model

501B's~

(1)

Model

400V,

(1}

Model

400C,

and

(1)

interconnecting

cable.

Not

included

with

the

system,

but

necessary

to

complete

it

is

(

l)

Elgar

3-phase

plug-in

oscillator.

The

system

is

connected

in

a

three-amplifier

3-phase

wye

configuration.

The

output

power

pwer

phase

is

500

VA

at

output

voltages

of

65VAC,

130VAC

or

260VAC

output

voltage.

1.

20

Whenever

a

standard

Elgar

System

has

been

ordered

with

a

cabinet,

the

system

model

number

will

be

preceded

with

the

letter

C.

Information

concerning

the

output

connections

of

any

of

the

standard

systems

appears

in

Section

II

of

this

instruction

manual.

Information

concerning

calibration

of

System

500-1

appears

in

Section

V.

Table

1-1.

Performance

Specifications

OUTPUT

INPUT

Power:

(VA)

Power

Factor

@

Full

VA

Voltage

Ranges

(VRMS)

Frequency

Range

(Hz)

Distortion

%@

Full

Load -

45-200 Hz

200-1000 Hz

1

000-5000 Hz

5000-1 0000 Hz

Voltage

(VAC)

Phase

Frequency

(Hz)

Power

(approx.max.W.)

PHYSICAL

Height

(in

& mm)

Width

(in

& mm)

Depth

(in

& mm}

Weight,

net

(lbs.

kg.)

shipping

(lbs.

kg.)

MODEL

251

B

250

±0.7

0-32,0-130,0-260

45-10000

0.6

0.4

0.6

0.9

115

or

230

Single

47-63

800

5.25

19

16

55

65

1-4

133

482

406

25

29

MODEL

501

B

500

±0.7

0-65,00-13010-260

45-5000

0.6

0.4

0.6

115

or

230

Single

47-63

1700

7.00

19.00

90

1

OS

178

482

41

47

.ti

.8

.7

10

'f.

DlSTOlmON

.5

.4

.3

.2

.I

0

100

80

GO

40

-,.OUTPUT VOLTS

Figure 1-1. Power

Output

Derating

-

--

IZOV

NO

LOAD

--

IZOV

FULL

LOAD

100

FREQUENCY

HZ

I

1.000

zo

0

~-,

/ '

/

Figure

1-2.

Typical Harmonic

Distortion

at

Rated Power

1-5

2.1 INTRODUCTION

SECTION

II

INSTALLATION

2.2

The

Model

251

B

and

Model

501

B Power Source have

been

calibrated

and

·

quality.

tested

prior

to

shipment.

The

unit

is,

therefore,·

ready·

for .installatl.on

and operation upon

receipt.

Instructions

in

this

section must be followed

to

ensure

proper

inspection upon

receipt

of

the

unit

and

to

ensure

correct

installation.

2.3

UNPACKING

AND

RECEIVING

.INSPECTION

2. 4 .

The

unit

has

been. packed

.in

accordance with

industrial

standards

for

safe shipment. Upon receipt

ofthe

unit,

unpack

and

inspect.

the

unit

as

described

in

the

following

steps:

. . . .

1. Visually

..

inspect

the

unit

exterior

for

any

signs

of

damage,

such

as

dents,

scratches,

or

distortion.

2. Check

the

front

panel controls for ease

of

operation.

3.

Ensure

that

the

front panel indicators

are

not damaged.

4.

Inspect

the

front

panel mounted meters

and

ensure

they

are

not

· damaged. · ·

s.

Remove

_the

top

cover

and

ensure

the

circuit

board

is securely

seated·

on

its

standoffs

and

that

the

five

connectors

going · · ·

.

to

it

are

also

securely

seated.

·Re-install

top

cover.·

·

.6.

If

the. power

source

has been equipped with a

plug-in

module,

remove and

inspect

it

for

any

signs

of

damage. Reinstall the

plug-in

module. Removal and reinstallation

of

the

plug-in

module

is

facilitated by

the

use

of

two

thumb-screws

located

on

the

front

of

the

plug-in

module.:

Insure

plug-in

module mates

securely

to

the

amplifier

board.

NOTE

If

obvious damage is evident, both the shipping agency and Elgar should

be

notified

immediately. It is important to save all shipping material for inspection. To notify Elgar

send a damage report

to

Elgar Repair Department. Elgar

in

return, will provide

instructions for repair or replacement

of

the damaged unit. Under

no

circumstances

should the unit

be

returned without the approval of Elgar.

2-1

ELGAR

Repair Department

9250 Brown Deer Road

San Diego,

CA

92121-2294

1-800-733-5427

Tel: (858) 450-0085

Fax: (858) 678-4482

www.elgar.com

2. 5

RACK

MOUNTING

2.6

Both power

sources

have

been

designed

to allow

rack

mounting. in a

standard

19-inch

instrument

rack.

The

physical dimensions

of

the

units

are.

given in Table

..

1.-1

of

Section

l.

2.7

For

slide.:.out"

capability,

the

power

sources

have

been

built

with

threaded

screw holes on

both

sides

of

the

unit

to

allow for installation

of

the

Zero Mfgs. Co.

chassis

slides,

pa.rt

number

CTN~120

•.

CAUTION

When

mounting

the

Model

2518

or

Model

5018,

ensure

that

the

flow

of

air

·into

the

fan

intake

or

outlet

is

not.

·

obstructed

or

serious

damage may

occur

· to

the

unit.

2.8

INSTALLAT.ION

2.9 Power

Requirements

2.10

This

AC

Power

Source

<?Perates from

either

115VAC

or

230VAC,

single

phase~

47

Hz

to

63

Hz

·input

power~

The

maximum

input

power

(approximately)

of

the

Model

2518

at

worst

case

is

1000

watts.

The

maximum

input

power ·

(approximately)

of

the

Model 5018

at

worst

case

is 1700

watts.

2.11.

·Unless

specified,

the

Model

2518

and

5018.

will be·

wired

for

115

VAC

input

voltage

operation.

·.For

230

VAC

oper.ation, remove

jumper

wire

from

3

.

and

pin 4

of

TB2. Locate

wire

connecting

TB2

1

to

input

transformer

Tl

2~

.·

Disconnect.

at

TB2

1.

and

reattach

to TB2 pin 4.

(Refer

to Fig.

7~1

and

Fig.

7-2,

Schematics in

Section

VII.}

· ·

. .

2.12. ·

Plug-In

Modules·

2.13

·In

most

cases,

the

Model

2518

and

Mod.el

5018

will

already

have

a

plug-in

oscillator,

signal-routing

plug-in

or

a

blank

panel

installed.

However~

in

the

event

installation

.of

one

of.

these

plug-in

modules is

necessary,

the

two

thumb screws will facilitate

their

installation

or

removal.

2.

llJ

External

Oscillators,

Programming

and

Synchronization

2.15 . In some

applications

it

may

be

desirable

to

use

an

external

oscillator

rather

than

an Elgar

plug-in

moduie. If

this

situation

exists,

the

blank

space

in

the

front

panel

should.

contain

a

blank

filler panel

(supplied

separately).

2-2

2.16 When

using

an

external

oscillator,

all

input

and

control

signals

should

be

connected

to

J1,

a

12-pin

Cinch-Jones

connector.

Jl

is

located

on

the

rear

panels

of

the

Model

251

B

and

Model

501

B.

(Refer

to

Figure

2-1 . )

Connector

Jl

may also

be

used

for

external

amplitude

programming

and

synchronization

of

the

internal

Elgar

plug-in

oscilla.to.r

to

an

external

timing

source.

It

is

important

to

know

that

when

an

external

oscillator

is

used,

the

input

impedance

must

be

matched

to

the

input

operational

amplifier

to

obtain

a

gain

of

1.

2.17

CHECKOUT

2.18

The

Model

251

B

and

501 B may be

checked

out

as

follows:

1.

Inspect

the

plug-in

oscillator.

2.

Connect

the

load

to

the

appropriate

terminal

of

the

rear

panel

power

output

terminal

block

(See

Figures

2-1

and

2-2).

For

bench-mounted

applications;

the

front

panel

binding

posts

may be

used

for

130V

output

only

on

the

Model

251

B.

The

front

panel

binding

posts

may

be

used

for

130V

or

260V

output

on

the

Model

50.1

B.

3.

Connect

the

input

power

cord

on

the

rear

panel

to

an

appropriate

source

of

single-phase

power.

4.

Set

the

front

panel

power

switch

to

the

ON

position.

The

indicator

lamp

that

lights

indicates

power

has been

applied

to

the

unit.

5.

Adjust

front

panel

AMPLITUDE

control

for

the

desired

output

voltage

as

indicated

on

the

front

panel

voltmeter.

2-3

CORD

Figure

2-1.

Modef2518

Rear

View.

TB30UTPUT

RTB

Figure

2-2.

Model

501

B

Rear

View

2-4

81

SECTION

Ill

OPERATION

3.1

INTRODUCTION

3.

2

This

section

describes

the

controls

and

indicators

of

the

Model

251

B

and

501

B.

The

controls

and

indicators

are

called

out

in

Figures

3-1

and

3-2.

The

functions

of

the

controls

and

indicators

are

given

in

Table

3-1.

(Refer

to

Oscillator

Instruction

Manual

for

a

description

of

the

controls

on

the

oscillator

plug-in

module.)

3.3

CONTROLS

AND

INDICATORS

3.4

The

controls

and

indicators

of

Model 251B

and

501B

is

described

in

Table

3-1.

TABLE

3-1.

CONTROLS

AND

INDICATORS

Control

and

Indicator

Function

Input

Power

Circuit

Breaker

CB1

Indicator

Lamp

DS1

AC

Voltmeter

M1

AMPLITUDE

Control

Potentiometer

R1

3-1

Applies

AC

input

power

to

unit.

Lights

to

indicate

power

has been

applied

to

unit.

Monitors

output

voltage

0-150

Adjust

input

signal

amplitude

of

oscillator.

OUTPUT

VOLTMETER

POWER

ON

SWITCH/Cl

RCUIT

BREAKER

M1

OUTPUT

VOL

CB1

CIRCUIT

BREAKER

Modei251B

ON/OFF

SWITCH

Model 5018

Figure 3-1.

Front

View

3-2

\

OUTPUT

POWER

BINDING

POSTS

OUTPUT

POWER

SECTION

IV

THEORY OF OPERATION

4.1

CIRCUIT

DESCRIPTION

(Refer

to

Figures

4-1,

7-1,

and

7-2)

4.2

The

input

signal,

approximately

3VRMS,

is

provided

by

the

plug-in

oscillator.

For

most

oscillators,

the

input

signal

amplitude

is

controlled

by

front

panel

AMPLITUDE

control.

The

signal

is

applied

to

the

first

amplifier

stage

of

differential

amplifier

Ql.

The

differential

amplifier

provides

high

DC

stability.

The

emitter

currents

are

supplied

by

R2

from

a +12V

supply

regulated

by

CR1.

The

output

of

Ql

is

coupled

to

the

base

of

Q2

which

provides

drive

signals

to

the

complementary

driver

stage,

Q6

and

QS.

QS

operates

as an

emitter-follower

to

drive

emitter-follower

Ql

of

upper

heatsink

assembly,

which

provides

base

drive

signals

to

the

upper

half

of

the

push-pull

class

B

power

amplifier.

Q6

is

operated

as a common

emitter

stage

to

provide

phase

inversion

of

the

drive

signals

to

the

lower

half

of

the

power

amplifier.

The

output

of

Q7

is

applied

to

emitter-follower

Q2

of

the

lower

heatsink

assembly

which

provides

base

drive

signals

to

the

lower

half

of

the

power

amplifier.

4.3

The

power

amplifier

consists

of

a

number

of

power

transistors

mounted

on

two

heatsinks.

The

.22 ohm

emitter

resistors

ensure

equal

current

sharing

of

the

output

transistors.

The

driver

and

output

stages

are

operated

from

nominal ±42VDC

supplies.

Thermal

switch

51

shown

on

heatsink

No.

1

turns

drive

signals

off

to

the

power

amplifier

in

the

event

the

power

amplifier

overheats

from

excessive

load

or

restricted

airflow

through

the

wind

tunnel.

4.4

The

power

amplifier

is

also

protected

from

overloads

or

short

circuits

on

the

output

by

current

limit

transistors

Q3

and

Q4.

The

current

in

the

upper

half

of

the

power

amplifier

is

sampled

by

R2

and

applied

across

upper

limit

adjustment

potentiometer

R25.

The

current

signal

is

then

applied

to

the

base

of

Q3

through

R18. When

the

voltage

at

the

base

of

Q3

reaches

Q3's

conduction

threshold

(approximately

0.6V)

the

drive

signal

is

diverted

from

the

base

of

QS,

preventing

any

further

increase

in

output

current.

Simultaneously,

the

current

in

the

lower

half

of

the

power

amplifier

is

sampled

across

R32

and

applied

across

lower

limit

adjustment

potentiometer

R4.

This

signal

is

then

applied

to

the

base

of

Q4

through

R22. When

the

voltage

at

the

base

of

Q4

reaches Q4's

conduction

threshold,

the

drive

signal

is

diverted

from

the

base

of

Q6

preventing

a

further

increase

in

output

current.

4.5

Amplifier

output

(TP2)

is

connected

to

output

transformer

T2,

which

steps

up

the

amplifier

voltage

to

the

required

output

level.

Negative

AC

feed-

back

path

is

from

TP2

through

RlS

to

a base

of

Ql.

Capacitor

C7

across

R15

is

used

to

prevent

high-frequency

oscillations

in

output.

Load

regulation

is

accomplished

by

passing

the

TP2

wire

from

the

heatsink

plug

through

a

current

4-1

-'==

I

IV

J1.4

EXT.

OSCILLATOR

INPUT

ELGAR

PLUG·

IN

OSCILLATOR

R1

AMPLITUDE

CONTROL

REGULATED

FEEDBACK

AC

FEEDBACK

Figure 4-1.

Modei251B

and

5018

Block Diagram

OUTPUT

j

transformer

T3.

Positive

current

feedback

is

taken

across

the

secondary

through

regulation

adjustment

potentiometer

R7

and

to

the

base

of

Q1

through

R8.

R7

and

CS

are

used

as

a

high-frequency

regulation

boost

network.

4.6

POWER

SUPPLIES

4.

7

Plus

and

minus 42VDC

for

the

amplifier

is

developed

by

the

full-wave

brrdge

rectifier

on

the

secondary

T1.

Filter

capacitors

and

supply

bleeder

resistors

R28

and

R29

located

on

the

amplifier

board

are

connected

across

the

output

of

the

bridge.

4.8

INTERCONNECTIONS FOR MULTI-PHASE OPERATION

4.

9 Two

or

three

Power

Sources

may

be

used

to

generate

two-phase

or

three-phase

AC

power.

Two-phase

or

three-phase

signals

are

generated

in a

two-phase

or

three-phase

oscillator.

installed

in

the

master

power

amplifier.

Signals

from

the

oscillator

are

carried

to

one

or

two

slave

power

amplifiers

{see

Figure-4-2),

each

of

which

has

a

blank

signal

routing

plug-in

which

makes

the

required

signal

interconnections

to

the

power

amplifier.

The

front

panel

AMPLITUDE

control

on

the

master

amplifier

controls

the

amplitude

of

all

the

amplifiers

outputs

simultaneously.

Upon initial

installation

of

the

system,

the

A

phase

power

amplifier

should

be

turned

on

first

and

the

output

voltage

adjusted

to

the

desired

level.

the

8

phase

unit

and

set

its

output

voltage

to

equal

the

A

phase

unit.

When

applicable,

repeat

for

C

phase

power

amplifier.

Some minor

adjustments

to

the

A,

8,

and

C

phase

units

will

be

necessary

to

initially

calibrate

the

system.

4.10

Two-phase

operation

requires

two

power

sources.

Three-phase

operation

may

be

accomplished

with

three

power

sources

in

wye

connection,

or

with two

power

sources

in

open-delta

connection.

A more

detailed

description

of

two-phase

and

three-phase

power

generation

is

provided

in

the

oscillator

instruction

manual.

4.11 In

the

open-delta

configuration,

two

power

amplifiers

of

equal

VA

rating

are

driven

by

a

standard

three-phase

oscillator

having

120°

phase

angle

between

0A,

08

and

0C. An

open

delta

requires

that

the

two

amplifiers

have

a

G0°

phase

angle

between

them

and

this

is

accomplished

by

inverting

the

second

amplifier.

4.12 In

these

systems,

the

amplifier

containing

the

plug-in

oscillator

is

referred

to

as

the

master

or

A-phase

source.

The

second

amplifier

is

referred

to

as

the

slave

or

8-phase

source.

·

4.13

The

open

delta

hook-up

shown

in

Figure

4-2

is

shown

as

a

vector

diagram

in

Figure

4-3.

4.14

Certain

specialized

oscillators

such

as

the

Super

Stable

(55)

series

and

the

Quasi-Square

wave

series

are

designed

only

for

open-delta

configurations

using

two

amplifiers

and

having

the

phase

angle

between

the

0A

and

08

drive

signals

at

G0°.

4.15 When

using

the

SS

series

or

quasi-square

wave

systems

the

intercon-

nections

would

be

as

shown

in

Figure

4-4.

4-3

Elgar 251B User manual

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