VOLTAGE SURGE PROTECTOR DIODE CR6

TM 11-5820-765-34

VOLTAGE SURGE PROTECTOR DIODE CR6:

Connected across transformer's power secondary winding.

Protects voltage regulator rectifier SCR1 (Q1) and bridge rectifier diodes CR1-CR4 from

transient voltage spikes.

V O L T A G E REGULATION CIRCUIT

Built into circuit card assembly PC101 (A1).

Controls firing time of silicon controlled rectifier SCR1 (Q1).

Keeps dc voltage at adjusted setting.

EXPLANATION:

SCR1 (Q1) fires twice each cycle of ac input voltage. By controlling firing time, SCR1 (Q1)

can be varied from full on when fired at start of each half-cycle to full off when fired

at end of half-cycle.

Bridge rectifier's dc output voltage can thus be varied from maximum possible voltage to

zero.

OVERVOLTAGE

CIRCUIT

CIRCUIT PARTS:

Silicon controlled rectifier SCR2 (Q2).

Low-resistance resistor R3.

Protects equipment being powered from overvoltages.

Activated when malfunction causes rise in output voltage.

ACTION:

C i r c u i t r y in PC101 (A1) senses trouble, fires SCR2 (Q2).

RESULTS:

Firing applies short-circuit load to output terminals which reduces output voltage to very

low value.

Short-circuit load opens circuit breaker CB1, which turns power supply OFF.

This prevents possible damage to power supply and equipment being pawered.

VOLTAGE ADJUST CIRCUIT (DC OUTPUT)

CIRCUIT PARTS:

Variable dc voltage adjust resistors R4, R8.

Stabilizing

capacitor

C3.

Fixed

resistor

R11.

CONNECTION:

Do output voltage fed through resistors to PC101(A1).

VOLTAGE

PATH:

output

negative

()

terminal

PC101

(A1).

Adjusts power supply's dc output voltage.

Activated when dc output voltage changes.

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