Quarter-Start Generator.

TM 11-6130-377-14

the voltage of the + input as long as the +120 vdc input

charge on capacitor C28 holds transistor Q10 on, which

voltage remains below approximately 142 vdc. If the

inhibits the voltage fault sensor circuits. U6-3 goes low

+120 vdc input voltage rises to approximately 142 vdc,

and provides a discharge path for capacitor C28 through

U9-6 goes low and Q9 turns on Q11 through R45.

resistor R42 and U6-3 to common. When capacitor C28

Transistor Q11 operates the shunt trip of CB1.

discharges to a voltage below the cutoff point of transistor

Q10 (approximately 50 milliseconds), the transistor turns

k. Shunt Trip Relay Driver. The shunt trip relay

off and removes the inhibit command from the voltage

driver consists of transistor Q11 and photocoupler U10.

fault sensors; that is, it allows the faults sensors to turn on

When transistor Q10 in the sensor delay circuit and

Q11 through Q9. The total delay prevents the faults

transistor Q9 in the high and low voltage fault sensor are

sensors from reacting to transients that may be present at

held off, the shunt trip driver is off. After the sensor delay

the turn-on of the inverter.

has timed out, turning off transistor Q10, either sensor U8

h. Quarter-Start Generator. The quarter-start gene-

or U9 turning on allows the base of transistor Q9 to go

low. This action turns on transistor Q11 and energizes the

rator consists of U6 and U7. During the 2 second power-

shunt trip through connector J1 pin 5. During parallel

on delay, U6-3 is off and transistor Q7 is on, grounding

operation, transistor Q9 turning on also forward-biases the

U7-5 and holding U7-6 low. With U7-6 low, U4-4 and -10

photodiode in the photocoupler (U10) and light from the

are low and the 60-Hz on U4-5 is inhibited. When U6-3

photodiode turns on the light-sensitive transistor. The

goes low, transistor Q7 turns off and U7-5 goes high. The

photocoupler is not used during nonparallel operation.

next 120 Hz-clock from U3-8 through Q8 to U7-2 causes

U7-6 to go high and stay high. When U7-6 goes high, U4-

l. Parallel Sensor Interconnection.

When the

4 and -10 go high and the 60-Hz signal is applied to Q4

inverter is connected for parallel operation of two units,

and Q5.

the photocoupler (U10) of the master inverter is

i. Low Voltage Fault Sensor. The voltage fault

connected to operate the slave inverter's shunt trip driver

and the photocoupler of the slave inverter is connected to

sensors monitor the +120 vdc input voltage at connector

operate the master inverter's shunt trip driver. This is

J1 pin 2 through voltage divider R29 and R30. The low

accomplished by use of the cable between connector P2

voltage fault sensor consists of operational amplifier U8

of each inverter drive circuit board. The collector of the

and transistors Q9 and Q11. A reference voltage is set

photocoupler transistor of the master inverter is

up at the + input of the operational amplifier by

connected through P2 pin 1 to +5 vdc of the slave inverter

potentiometer R32 and resistors R31 and R33.

at connector P2 pin 3. The emitter of the master inverter

Potentiometer R32 is set so that the voltage of the + input

photocoupler transistor is connected through connector

is above the voltage of the - input as long as the +120 vdc

P2 pin 4 to the base of shunt trip driver transistor Q11 of

input voltage remains above approximately 95 vdc. If the

the slave inverter at connector P2 pin 9. When the

+120 vdc input voltage drops to approximately 95 vdc,

master inverter photocoupler transistor turns on, the slave

the + input drops below the - input. This action causes

inverter +5 vdc is conducted to the .base of transistor Q11

the output to go low which turns on transistor Q9. When

in the slave inverter, causing the shunt trip drivers to

transistor Q9 turns on, Q21 is turned on through R45 and

operate simultaneously. The photocoupler of the slave

causes the shunt trip of CB1 to operate.

inverter operates the shunt trip driver of the master

j. High Voltage Fault Sensor. The high voltage fault

inverter similarly, except that master inverter +5 vdc is

sensor consists of operational amplifier U9 and transistors

obtained at slave inverter connector P2 pin 10. Other

Q9 and Q11. The high voltage fault sensor operates

connections to connector P2 during parallel operation are

similar to the low voltage fault sensor, except that the

described in the parallel SCR driver input description.

amplified inputs are reversed. Potentiometer R37 is set

so that the voltage of the - input of the amplifier is below

Change 1

5-9