Chapter 5. FUNCTIONING OF EQUIPMENT

CHAPTER 5

FUNCTIONING OF EQUIPMENT

s i l i c o n controlled rectifier is fired will deter-

5-1. Circuit Description

mine the output voltage amplitude. Conduction

Single phase, 115 volts, 60 cycles per second

o f the silicon-controlled rectifier applies dc

( c p s ) , is applied to the primary windings of

v o l t a g e to the power supply output terminals

v a r i a b l e transformer T3 and auxiliary power

f o r the remainder of that half cycle. The gate

t r a m f o r m e r T1. Transformer T3 controls the

current pulse will then be applied to the outer

v o l t a g e to the power transformer T2 primary

silicon-controlled rectifier w h e n positive volt-

w i n d i n g s . The power transformer T2 second-

age is applied to the anode.

ary voltage is applied to the silicon-controlled

rectifiers SCR1 and SCR2 anodes, and diodes

52. Circuit Regulation

C R 4 and CR5. The auxiliary power trans-

T h e negative output terminal is connected

f o r m e r T1 secondary voltage is applied to

to the output sense terminal. The output volt-

d i o d e s CR2 and CR3. Through the full-wave

age is then applied to variable resistor R3 and

rectifying action of diodes CR2 and CR3 and

compared with the reference voltage. If a dif-

t h e clipping action of diode CR1, a 20-volt

f e r e n c e in the output and reference voltages

a m p l i t u d e square-wave reference voltage is

exists, the difference will be amplified by am-

f o m e d . Transistor Q4 provides regulation of

plifier transistor Q1. Transistor Q1 output will

the reference voltage. Zener diode CR6 clamps

turn transistor Q2 on. Resistor R5 and capaci-

t h e transistor Q4 base voltage. The reference

tor Cl comprise a stabilizing feedback circuit.

v o l t a g e is then applid to the pulse generator

Transistor Q2 then assumes a collector current

unijunction transistor Q3 base to develop a

such that the output voltage error is corrected.

g a t e current pulse as determined by the time

Choke Ll, resistor R16, and capacitor C5 form

constant of resistor R8 and phase-delay capaci-

t h e output voltage filtering network. Variable

tor C3. The gate current pulse is applied to fire

transformer T3, variable resistor R3, and

the silicon-controlled rectifier having a positive

v o l t a g e vernier resistor R2 adjust the power

voltage applid to the anode. The time that the

supply output level.

5-1