Diy Barberpole Indicator

Figure 2. 5-2. Electrical Power Subsystem - Power Interface Diagram (Sheet 3 of 3)

A-C power is provided to LM subsystems by either of two identical, redundant inverters; it is controlled by the EPS: INV 1 and ENV 2 circuit breakers (panel 11 and 16, respectively), the INVERTER switch, and the AC BUS A: BUS TIE or AC BUS B: BUS TIE circuit breakers on panel 11. The EPS: INV 1 or INV 2 circuit breaker supplies 28 volts dc from the LM Pilot's or Commander's 28-volt d-c bus to the chosen normally synced inverter, where the dc is changed to 115-volt, 400-cps, a-c power (350 volt-amperes, steady-state). The INVERTER switch selects the output of either inverter and routes it to the a-c buses via the respective AC BUS: BUS TIE circuit breakers. Normally, inverter No. 2 is energized when the LM subsystems are first activated and connected to the a-c buses. Inverter No. 1 functions as backup during the mission, except that it is the operating inverter during DPS and APS engine burns. An a-c bus voltage and frequency readout signal is supplied from a-c bus A, via the AC BUS A: AC BUS VOLT circuit breaker (panel 11), to the IS for telemetry and caution light display. An out-of-tolerance frequency (less than 398 cps or more than 402 cps) or a low-voltage condition (less than 112 volts ac) causes the INVERTER caution light (panel 2) to go on. The astronaut determines the cause of the malfunction and performs corrective action. The INVERTER caution light goes out when the malfunction is remedied. (When the INVERTER caution light goes on, the MASTER ALARM pushbutton/light on panels 1 and 2 goes on and a tone is generated for the astronaut headsets. Pressing either MASTER ALARM pushbutton/light extinguishes the pushbutton/lights and terminates the tone.) When set to AC BUS. the POWER/TEMPMON selector switch (panel 14) selects a-c bus A for voltage display on the VOLTS indicator (panel 14); the reading on the AMPS indicator has no significance.

2. 5. 3.4 Power Monitoring.

The primary a-c and d-c voltage levels, d-c current consumption, and the status of all main power feeders must be monitored periodically to ensure availability of proper power for all LM subsystems, throughout the mission. This monitoring is normally the responsibility of the LM Pilot, who controls the ELECTRICAL POWER portion of panel (14). This panel has talkbacks that indicate main power feeder status, indicators that display battery and bus voltages and battery current, and component caution lights that are used for detecting shorted buses or main power feeder lines and for isolating a malfunctioning battery. Availability of redundant a-c and d-c power permits the astronaut to disconnect, substitute or reconnect batteries, feeder lines, buses, or inverters to assure a continuous electrical supply. Battery Status-Monitoring Circuits. (See figure 2. 5-6.)

Talkbacks on panel 14 indicate the status of the descent and ascent batteries (on or off the line). A DESCENT POWER talkback barber-pole display signifies that the related battery is disconnected from its main power feeder; a gray display, showing LO, that the battery low-voltage tap is connected to the power distribution system via the main power feeder; a gray display, that the high-voltage tap is connected to the power distribution system. A DES BATS talkback gray display signifies that the descent battery outputs are connected to the ascent stage; a barber-pole display, that these power lines are disconnected and the ascent stage is isolated electrically from the descent stage. The ASCENT POWER talk-backs indicate that their related ascent battery is connected (gray) or disconnected (barber pole) from

I the respective normal feed or backup feed main power feeder lines. The LUNAR BAT talkback CDR, LMP, and barber-pole displays indicate that the lunar battery is on the CDR bus, the LMP bus, or is off-line.

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