EG&G ORTEC 402D Bedienings- en onderhoudshandleiding - Pagina 12

Blader online of download pdf Bedienings- en onderhoudshandleiding voor {categorie_naam} EG&G ORTEC 402D. EG&G ORTEC 402D 16 pagina's.

Pagina afdrukken

OPERATING INSTRUCTIONS

4.1

POWER SUPPLY LIMITATIONS

The available current from the Power Supply is given in

Section 2. Care must be used to ensure natural convec

tion of heat dissipated by the heat sinks and power trans

former. For best resuits, when using at maximum power

loadings, the Bin and Power Supply should be in an open

space, piaced upon blocks at least 1 in. off the table

mounting surface to allow maximum ventilation. When

used in a rack, maximum attention should be paid to

placement of other heat-generating equipment. Ade

quate unobstructed space on all sides is necessary for

convection ventilation and cooling. If the Bin contains

other heat-generating equipment, a blower may be

advisable to remove the dissipated heat.

When it is necessary to rack-mount severai bins and

power supplies, especially when other heat-generating

equipment is located within the rack, the term "ambient

temperature" becomes less clearly defined. A better

guide to maximum power loading capability is to monitor

the heat sink temperature. Never allow the heat sink

temperature to continuously run above lOCC. Although

this is not the maximum operation temperature, any addi

tional temperature rise due to other conditions of the sys

tem may force the Supply out of tolerance and may cause

it to automaticaily shut down operation. Should your

operation produce a temperature of 100°C, a blower to

remove the dissipated heat is recommended.

4.2

6-V POWER SUPPLIES CROWBAR

OPERATION

Both the -f-e-V and the -S-V outputs are protected

against overvoltage. If for any reason one of these output

voltages exceeds 7.5 V maximum in absolute value an

internal "crowbar circuit" is triggered, which places a

short-circuit across the output of the corresponding volt

age. Since this circuit contains an SCR, normal opera

tion, after suppression of the cause of the overvoitage,

can be resumed only by turning the power switch of the

4001 Bin to Off for a couple of seconds, and then turning it

to On again.

If in normal operation it is suddenly discovered that the

+6-\/ or -6-V output is missing, first check whether it can

be restored by following this procedure, after having

removed all the modules from the Bin. The crowbar pro

tection circuit of the corresponding voitage may have

been triggered by a temporary fault in one module or

even by a strong spurious voltage transient.

5. CIRCUIT DESCRIPTION

5.1. GENERAL DESCRIPTION

The 402D Power Supply produces six dc output voltages;

±12 V, ±24 V, and ±6 V. A power transformer reduces the

input ac line volfage into six separate low voltage

sources. Each voltage source has a separate full-wave

bridge, a filter capacitor, and an electronic series regula

tor. Each regulator is composed of discrete solid-state

devices and is completely independent from all other

output regulators.

The six regulators are packaged on three plug-in printed

circuit boards. The board closest to the heat sink

includes regulators for the ±6 V supplies. The board in

the middle includes regulators for the negative 12 and 24

V supplies. The other board includes regulators for the

positive 12 and 24 V supplies. The 12 V and 24 V regulator

boards are identical and may be interchanged.

The rectifiers, series pass transistors, sense resistors,

and the SCRs for the 6 V supplies are all located on the

large heat sink. The filter capacitors for the 12 V and 24 V

supplies are located on their regulator boards. The filter

capacitors for the 6 V supplies are mounted in the power

suppiy chassis.

5.2. OPERATION OF REGULATORS

The operation of the ±12 V and ±24 V regulators are all

identical. The +24 V regulator is discussed here as an

example that is typical for all four of these supplies. The

circuit is shown on schematic 402D-0201-S1.

The circuit consists of two parts; these are the voltage

regulator and the current foldback circuit. The voltage

regulator includes Q10, Q11, Q3, Q4, Q2, Q1, and Q101.

The current foldback circuit includes Q5, Q7, Q8,06, and

09.

Transistors 010 and Oil operate as a differential ampli

fier, comparing the voltage from the reference diode, D4,

at the base of 010 to the output voltage divided down by

resistors R21, R22, and R23. Potentiometer R22 is used to

adjust the output voltage to the desired level. The differ

ence voltage is amplified by 03 and 04 to reduce the

current through 02 and to increase the output voltage or