8
VI. FUNCTlONAL DESCRIPTlON OF VARlOUS MODULES :
1. Mains Transformer : This trasnformer is mounted on a plate towards the Rear
Panel . This takes 230V/110V A.C. and steps it down to 16V, 10V & 5V A.C.
voltages required for generating dc power.
2. P.T. Transformer : This is also mounted on the plate towards the Rear Panel &
steps down PT input from 110V AC to 3.3V AC. which is used for sensing
PT voltage.
3. Main PCB : This module generates ±12V DC, +5V DC required for circuit
operation. Three pin regulator ICs 7812, 7912, 7805 are used to
give regulated +12V, -12V & + 5V D.C. Supplies. The PT input is stepped
down in the ratio 110/3.3. This stepped down voltage is rectified, filtered and
amplified by IC10. This voltage is used for comparison with reference voltage
settings (on Display PCB). L, R, UV/OV signals are received from Display PCB.
On receiving any of L or R signals, IC5 generates Time Delay followed by LR and
RR commands generated by IC4 for energizing appropriate relay. The NO
contacts are brought out on the Rear Panel Terminal Block. In case of UV/OV
condition, the relays are blocked and no control pulses are available. The IC8 is
used to convert the analog voltage to digital voltage and display the same on 7
segment display on Display PCB.
4. Display PCB : R set, Nom set, L set potentiometers allow the required settings
to be set. The L, R, UV, OV settings are compared with the DC output by IC3
and the L, R, UV/OV LEDs indicate these conditions. Selector switch selects
the Nominal Value L and R settings and PT I/P to be displayed on the 7 segment
display. LR, RR LEDs indicate the relay operation condition.Time Delay
potentiometer allows the required time delay to be set.
5. IC1 generates 15 minutes delay for CFR condition which is indicated by CFR
LED.
6. When LDC option is required %R & %X potentiometers allow for %R & %X
compensation. SW3 & SW4 allow for polarity selection. IC7 sums the PT I/P &
LDC O/P.
7. TPI PCB : This PCB generates constant current which is used for generating
100mV per step. The IC2 is used to convert analog voltage to digital voltage &
display the same on 7 segment display.
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