PSC 101 - Theory of Operation

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ЗЕСПОМ

3

THEORY

OF

OPERATION

MOD

power

sources

are

all-silicon

voltage

and

current

regulated

modules.

The

units

are

designed

to

operate

on

a

line

voltage

ranging

from

105

to

130

volts

AC

at

a

line

frequency

ranging

from

50

to

60

Hz.

The

power

source

consists

of

six

basic

elements:

(1)

the

power

transformer,

rectifier

and

filter,

(2)

an

auxiliary

DC

supply,

(3)

a

reference,

with

voltage

and

current

amplifiers,

(4)

the

automatic

crossover

circuit,

(5)

an

optional

overvoltage

crowbar

circuit,

and

(6)

the

series

control

element.

The

line

voltage

is

connected

to

the

primary

of

transformer

Т1;

the

output

of

secondary

No.

1

of

TI

is

connected

to

an

AC-to-DC

conversion

unit.

The

conversion

unit

consists

of

a

fullwave

bridge

rectifier

anda

large

capacitor.

The

positive

(+)

output

is

connected

to

the

positive

output

terminal

via

the

series

control

element.

The

negative

(-)

output

is

connected

directly

to

the

negative

output

terminal.

The

auxiliary

DC

supply

power

is

supplied

by

secondary

No.

2

of

transformer

T1

and

rectified

by

a

full-

wave

bridge

and

filtered

by

capacitor

C3.

The

auxiliary

DC

supply

provides

a

regulated

plus

(+)

13

volts

and

minus

(-)

13

volts

(with

respect

to

the

positive

(+)

output

of

the

unit)

to

the

regulator

board.

The

regulator

board

consists

of

a

voltage

and

current

reference,

two

low-drift

differential

amplifiers

(one

for

voltage

and

one

for

current),

an

analog

OR

circuit,

anda

driver

amplifier

for

the

series

control

ele-

ment.

The

voltage

servo

is

connected

in

an

operational

configuration

and

the

current

servo

is

connected

in

a

potentiometric

configuration.

The

analog

OR

circuit

provides

automatic

crossover

from

voltage-to-

current

and

current-to-voltage

regulation.

The

most

negative

voltage

to

the

two

inputs

of

the

analog

OR

circuit

determines

the

mode

of

regulation.

The

supply

may

operate

in

both

modes

simultaneously

if

the

inputs

to

the

analog

OR

circuit

are

of

an

equal

magnitude.

The

optional

overvoltage

crowbar

circuit

consists

of

an

adjustable

level

detector

and

a

silicon

controlled

rectifier

(SCR).

The

purpose

of

the

overvoltage

crowbar

is

to

protect

external

equipment

from

possible

power

supply.

failure

or

the

operator

from

truning

the

voltage

up

too

high.

When

the

voltage

reaches

a

pre-selected

point

the

SCR

is

turned

on

and

the

output

of

the

supply

is

short-circuited.

In

order

to

re-

turn

the

supply

to

normal

operation,

adjust

the

voltage

control

to

zero

volts

and

then

back

to

the

desired

voltage.

FRONT

PANEL

VOLTAGE

POWER

TRANSFORMER

RECTIFIER

AND

FILTER

CAPACITOR

ANALOG

VOR”

CIRCUIT

PASS

TRANSISTOR

ASSEMBLY

CURRENT

-

NSE

RESISTOR

FRONT

PANEL

MOD

POWER

SUPPLY

BLOCK

DIAGRAM

FIGURE

3-1