1. AC POWER REQUIREMENTS & AC TO AC CONVERTER
CECOM LAR Tropo Operation Course
AC POWER REQUIREMENTS & AC TO AC CONVERTER
CECOM LAR Course
Logistics Assistance Division
Fort Gordon, Georgia
In this class we will discuss the AC Power requirements and AC to AC converter operation for the all models of TROPO systems.

2. CECOM LAR Tropo Operation Course
Purpose
AC Input is required to power the TROPO system.
TROPO Power requirements are:
AN/TRC-170(V)2 – 30 KW
AN/TRC-170(V)3 W/O ECU 10 KW
AN/TRC-170(V)5 with ECU 15 KW
Now lets discuss the AC Voltage and Power requirements for the TROPO systems:
1. AC 3 Phase Voltage input is required to power the TROPO systems.
2. The AN/TRC-170(V)2 requires a power source of 30 KW.
3. The AN/TRC-170(V)2 requires a power source of 10 KW when no ECU’s are utilized.
4. The AN/TRC-170(V)2 requires a power source of 15 KW when an ECU’s is utilized.

3. AC Input Power Requirements
CECOM LAR Tropo Operation Course
AC Input Power Requirements
Prime Power Frequency: 50, 60 or 400 Hertz
Frequency Tolerance: Hz, Hz
Prime Power Voltage Phases A, B, & C
108 to 132 VAC
Will shut down if any phase is more than 140 VAC or less than 100 VAC.
All phases must be within 5 VAC of each other.
Now lets continue discussing the AC Voltage and Power requirements for the TROPO systems:
1. Prime Frequency is 50, 60 or 400 Hertz.
2. Frequency Tolerance is 47 to 62 Hertz and 380 to 420 Hertz.
3. The system requires a 3 Phase power source. The Phases are A, B, and C. Neutral and ground are also required.
4. Voltage input tolerance is 108 to 132 VAC.
5. System will shut down by design if any phase is more than 140 VAC or less than 100 VAC.
6. All phases must be within 5 VAC of each other or system will also shut down.

4. Prime Power Current Draw
CECOM LAR Tropo Operation Course
Prime Power Current Draw
No HPA – 5 Amps each phase
HPAs in High Power
1 HPA – 30 Amps each phase
2 HPAs – 55 Amps each phase
Main Circuit Breaker
TRC-170(V)2 – Amps
TRC-170(V)3 – Amps
Let discuss the Prime Power Current Draw and requirements for the TROPO systems:
1. With no High Power Amps (HPAs) turned on, five (5) amps will be drawn on each phase.
2. When the HPA is in the High Power Mode. With one HPA on thirty (30) amps is drawn on each phase.
3. When the HPAs are in the High Power Mode. With two HPAs on fifty-five (55) amps is drawn on each phase.
4. The Main Circuit Breaker utilized in the AN/TRC-170(V)2 is a ninety (90) amp breaker.
5. The Main Circuit Breaker utilized in the AN/TRC-170(V)3 is a sixty (60) amp breaker.

5. CECOM LAR Tropo Operation Course
Over/Under Relay K1
Trips the Interior Main Prime Power Circuit when:
Over voltage of 140 VAC or under voltage of 100 VAC condition exists.
Will also trip if a five (5) volt difference occurs between any two phases.
Now lets discuss the Over/Under Relay K1 and how it functions with the input AC voltage requirements of the TROPO systems.
1. The Over/Under Voltage Relay K1 in the Power Distribution is designed to protect the TROPO system from a Over or Under Voltage condition.
2. Relay K1 trips the Interior Main Circuit Breaker when an over voltage condition of 140 VAC or greater is present on any one of the three (3) phases.
3. Relay K1 trips the Interior Main Circuit Breaker when an under voltage condition of 100 VAC or less is present on any one of the three (3) phases.
4. Will also trip the Interior Main Circuit Breaker if there is a five (5) volt difference occurs between any of two phases.
5. This Relay K1 functions the same for all models of the TROPO system.

6. Prime Power Cable Pin-Outs
CECOM LAR Tropo Operation Course
Prime Power Cable Pin-Outs
LINE CABLE CONNECTOR PIN
Phase A A
Phase B B
Phase C C
Neutral N
Safety Ground G1
Safety Ground G2
Safety Ground G3
Safety Ground G4
Now lets discuss the Main AC Power cable utilized with the TROPO systems.
1. Here is how the Main Power Cable that connects to connector J1 on the Power Entry Panel is configured.
2. Phase A is connected to Pin A, Phase B is connected to Pin B, and Phase C is connected to Pin C.
3. Neutral is connected to Pin N.
4. The Safety Grounds 1-4 are connected to G1 through G4.

7. CECOM LAR Tropo Operation Course
Power Entry Panel
Now lets discuss the functional operation for the Power Entry Panel for all the TROPO systems Refer to FO 2-1
1. The Power Entry Panel accepts three 3-Phase voltage (Phase A, B, & C) along with Neutral and ground to power the TROPO systems.
2. The main system ground is located on the Power Entry Panel.
3. The Power Entry Panel is located on the Roadside of the shelter for both the AN/TRC-170(V)2 and the AN/TRC-170(V)3 systems.
4. The Power Entry Panels are almost same with these two exceptions: the ECU Circuit Breaker is different because of the more current capability and the ECU Power connector is also larger for the V2 because of the more current capability required by the 18 thousand BTU ECU. This assembly will be covered once for both systems.
5. The Surge Protection Fault Assembly is in parallel with the 3 Phase input AC voltages and Neutral.

8. Power Entry Panel Voltage & Current Flow
CECOM LAR Tropo Operation Course
Power Entry Panel Voltage & Current Flow
Now lets discuss the voltage and current flow for the Power Entry Panel Refer to FO 2-1
1. Connector J1: accepts 3 Phase Power in and the 3 Phases and Neutral are paralleled with the Surge Protection Fault Assembly.
2. Surge Protection Fault Assembly: When a High Voltage surge occurs the Metal Oxide Arrestors (MOV) will short causing the fuse to blow, and the associated lamp to light. The system will continue to operate but with no protection on that associated phase or Neutral. This item is the same in all models of the TROPO systems.
3. Transformers T1, T2, T3: the inducted input voltage is taken off the main power input via transformer windings T1, T2, and T3. 4. The output of these transformers are sent to RFI filters FL2 through FL5.
4. RFI FL2 through FL5: these RFI filters blocks any RF signals riding on the AC input voltages and neutral. The outputs of these RFI filters is passed to the Power Distribution Assembly monitor metering circuits.
5. RFI Filter FL1: filters Phases A, B, C, & Neutral prior to leaving the Power Entry Panel.
6. The Power Entry Panel: is the very similar for both TROPO systems with the exceptions of the Exterior and ECU circuit breakers to include the ECU power connector on the V2 for a higher current capability. It is located on the Roadside of the shelter.

9. Power Entry Panel Voltage & Current Flow continued
CECOM LAR Tropo Operation Course
Power Entry Panel Voltage & Current Flow continued
Now lets continue our discussion on the Power Entry Panel Refer to FO 2-1
1. Exterior Main Circuit Breaker CB1: this fifty (50) amp circuit breaker receives 3-Phase AC voltages from connector J1. When closed allows all three (3) phases to be applied to the ECU Circuit Breaker CB2.
2. ECU Circuit Breaker CB2: when closed allows all 3-phases to be passed to connector J6 called the ECU power.
3. External (Ext) Convenient (CNVC) Outlet Circuit Breaker CB4: is a fifteen (15) amp circuit breaker. When closed allows Phase A to be passed to connector J7 called CNVC Outlet.
4. ANT ½ Deicing Circuit Breaker CB5: is a five (5) amp circuit breaker. When closed allows Phase B to be passed to connector J8 and J9.

10. Power Entry Panel Control & Indicators
CECOM LAR Tropo Operation Course
Power Entry Panel Control & Indicators
Now lets discuss the Power Entry Panel Control & Indicators
1. Exterior Main Circuit Breaker: Applies prime power to the shelter exterior and provides overload protection. CB1 is a 3-phase circuit breaker.
2. ECU connector: power connection for environmental control unit (air conditioner)
3. ANT 1 DEICING connector: for antenna 1 de-icing cable
4. CNVC OUTLET connector: for accessory equipment
5. ANT 2 DEICING connector: connector for antenna 2 de-icing cable
6. PRIME POWER connector: for 208 VAC 3 phase or 400 Hz connector for prime power from external source.
7. CNVC OUTLET Circuit Breaker: applies power to CNVC OUTLET connector and provides overload protection. CB4 is a single-phase 15-amp GFI breaker.
8. ANT 1 / 2 DEICING Circuit Breaker: applies power to DEICING connectors and provides overload protection. CB3 is a single-phase 5-amp breaker.
9. ECU PWR Circuit Breaker: applies power to ECU connector and provides overload protection. CB2 is a 3-phase 35-amp breaker.
10. GROUND terminal lug: external ground terminal connection for shelter ground.

11. Surge Protection Fault Assembly
CECOM LAR Tropo Operation Course
Surge Protection Fault Assembly
Now lets discuss the Surge Protection Fault Assembly in the Power Entry Panel refer to FO 2-1.
1. Surge Protection Fault Assembly: uses metal oxide varistors, one for each phase A, B, C, and neutral.
2. When a high voltage surge has occurred: the MOV will absorb the high voltage surge and it will short circuit to ground , causing the lamp to light alerting the operator that a high voltage surge has shorted the MOV.
Each phase and neutral: has an individual fuse in parallel with the lamps. The surge protection fault assembly is connected in parallel with each input leg and neutral.
The system can continue to operate but with out surge protection. This means that if another high voltage spike occurs on that same leg it may damage the equipment. The Surge Protection Fault Assembly is the same in both the AN/TRC-170(V)2 and AN/TRC-170(V)3 systems.

12. Power Distribution Panel (V)3
CECOM LAR Tropo Operation Course
Power Distribution Panel (V)3
Now lets discuss the AC Input Voltage & Current Flow through the Power Distribution Panel Assembly for the (V)3. Please refer to FO 2-2a.
1. Switch S1 Meter Transfer Switch Phase Select: This input power is used by the Phase Select switch S1 and allows monitoring of the current draw for each input phase by ammeter M3. Allows monitoring of the voltage and frequencies of each input phase by voltmeter M4 and frequency meters, M1 for 50/60 hertz and M2 for 400 hertz. Control Circuit Breaker CB13 protects these meters.
2. Control Circuit Breaker CB13: Receives Phase A, B, and C from the Power Entry Panel. Must be activated for the TROPO system to power up. Applies power to the Over/Under Voltage Relay K1 and Phase Select Switch 1. Provides protection for the meters M1 through M4 and Switch S1. If this circuit breaker opens, it will illuminate the Control CB Tripped Lamp DS1 on the Power Distribution Panel. This Control Circuit Breaker CB13 is on the inside of the Power Distribution panel along with fuse F1.
3. Over/Under Voltage Relay K1: The K1 Relay monitors the Voltage & Frequency of the input power. The voltage from each leg to neutral is 120 VAC  10 %. Should any phase exceed 140 VAC or be less than 100 VAC, a sensor circuit in the Over/Under voltage relay will cause K1 to denergize causing the Interior Main Prime Power Circuit Breaker CB1 contacts to open removing power from all units in the shelter. Also, a five (5) volt difference between any two phases will cause K1 to denerigize causing CB1 contacts to open removing power from the shelter.

13. Power Distribution Panel (V)3 continued
CECOM LAR Tropo Operation Course
Power Distribution Panel (V)3 continued
Now lets continue to discuss the AC Input Voltage & Current Flow through the Power Distribution Panel Assembly for the (V)3. Please refer to FO 2-2a.
1. Interior Main Prime Power Interrupt Circuit Breaker CB1: Next the AC Power comes to the Interior Main Prime Power Circuit Breaker. This circuit breaker is a 3-phase 60-amp circuit breaker. Power is then applied to all the other circuit breakers on the Power Distribution Panel Assembly. If voltage is removed from the coil of this circuit breaker it will cause this circuit breaker to open removing power from inside the shelter.
2. Circuit Breakers CB2: this circuit breaker is a 3-phase 30 amp circuit breaker that when closed provides 3-phase power to the High Power Amplifier (HPA).

14. Power Distribution Panel (V)3 continued
CECOM LAR Tropo Operation Course
Power Distribution Panel (V)3 continued
Now lets continue to discuss the AC Input Voltage & Current Flow through the Power Distribution Panel Assembly for the (V)3. Please refer to FO 2-2b.
Fan Power Converter (AC-to-AC Converter) Circuit Breaker CB10: this circuit breaker is a 3-phase 10-amp circuit breaker. When closed allows 3-phase power to be applied to AC-to- AC converter assembly.
2. Circuit Breaker CB9: this circuit breaker is a 3-phase 20-amp circuit breaker. When closed allows 3-phase power to be applied to the shelter heater assembly.
3. Circuit Breaker CB8: this circuit breaker is a 3-phase 10-amp circuit breaker. When closed allows 3-phase power to be applied to both of the Low Voltage Power Supplies.
4. Circuit Breakers CB8 & CB9: both these circuit breakers can be tripped if the coil is energized by the +28vdc that is applied through Thermal Switch S1 in the Road Side Air Duct Assembly (4A4) and Curb Side Air Duct Assembly (7A5). If the temperate reaches 150 degrees Fahrenheit the contacts in the Thermal Switch will close, applying +28vdc to the coils of these circuit breaker CB8 and CB9, causing these circuit breakers to open. The circuit breakers that are affected by this circuitry are; the DGM Group, DLED1/ 2, LVPS 1/ 2, and the Shelter Heater.

15. Power Distribution Panel (V)3 continued
CECOM LAR Tropo Operation Course
Power Distribution Panel (V)3 continued
Now lets continue to discuss the AC Input Voltage & Current Flow through the Power Distribution Panel Assembly for the (V)3. Please refer to FO 2-2c.
1. Circuit Breaker CB6 DGM Equipment: this circuit breaker is a single phase 10-amp circuit breaker. When closed allows voltage to be applied to the DGM equipment.
2. Circuit Breaker CB7 DLED 1 & 2: this circuit breaker is a single phase 2-amp circuit breaker. When closed allows voltage to be applied to the KG-84 DLEDs 1 & 2.
3. Circuit Breaker CB12 CNVC Outlets: this circuit breaker is single phase 15-amp circuit breaker. When closed allows voltage to be applied to the convenience outlets.
4. Circuit Breaker CB5 Vent Fan: this circuit breaker is single phase 2-amp circuit breaker. When closed allows voltage to be applied to the Vent fan.
5. Circuit Breaker CB4 Lights: this circuit breaker is single phase 5-amp circuit breaker. When closed allows voltage to be applied to the shelter lights.
6. Circuit Breakers CB6 & CB7: both these circuit breakers can be tripped if the coil is energized by the +28vdc that is applied through Thermal Switch S1 in the Road Side Air Duct Assembly (4A4) and Curb Side Air Duct Assembly (7A5). If the temperate reaches 150 degrees Fahrenheit the contacts in the Thermal Switch will close, applying +28vdc to the coils of these circuit breaker CB6 and CB7, causing these circuit breakers to open. The circuit breakers that are affected by this circuitry are; the DGM Group, DLED1/ 2, LVPS 1/ 2, and the Shelter Heater.

16. Power Distribution Panel (V)3 Controls & Indicators
CECOM LAR Tropo Operation Course
Power Distribution Panel (V)3 Controls & Indicators
Now lets discuss the Power Distribution Panel Assembly Control and Indicators for the (V)3.
1.INTERIOR MAIN - prime power interrupt circuit breaker Applies prime input power to shelter equipment and provides overload protection. CB1 is a 3-phase 60-amp breaker.
2. HPA – circuit breaker Applies prime power to the power amplifier and provides over­ load protection. CB2 is a 3-phase 30-amp breaker.
3. CONTROL CB TRIPPED - indicator lamp (red) indicates control circuit breaker is open.
4. FREQUENCY METER- a reed-type frequency meter that indicates 400 Hz line frequency.
5. PHASE SELECT – switch selects phase A, B, or C of primary power to be monitored by meter.
6. VOLTS – meter indicates the voltage of phase A, B, C of primary power.
7. LIGHT INTLK OVERRIDE - NORMAL – switch in OVERRIDE position, the shelter interior lights remain on when door is opened. In NORMAL position, the shelter interior lights turn off when door is opened and red blackout light comes on.
8. DGM GROUP - circuit breaker Applies prime power to LGM 1, GM, TGM, and LGM-2 or LSCDM and provides overload protection. CB6 is a single-phase 10-amp breaker.

17. Power Distribution Panel (V)3 Controls & Indicators
CECOM LAR Tropo Operation Course
Power Distribution Panel (V)3 Controls & Indicators
Now lets continue the discussion the Power Distribution Panel Assembly Control and Indicators for the (V)3.
9. DLED ½ - circuit breaker applies prime power to DLED 1 & 2 and provides overload protection. CB7 is a single-phase 2-amp breaker.
10. SHELTER HEATER – circuit breaker applies prime power to shelter heaters and provides overload protection. CB9 is 3-phase 20-amp breaker.
11. INTR CNVC OUTLET – circuit breaker applies prime power to convenience outlets in shelter and provides overload protection. CB12 is a single-phase 15-amp breaker.
12. FAN PWR CONV - circuit breaker applies prime power to AC-to-AC Converter and provides over­load protection. CB10 is 3-phase 10-amp breaker.
13. LVPS 1 / 2 - circuit breaker applies prime power and provides overload protection for both Low Voltage Power Supplies. CB8 is a 3-phase 10-amp breaker.
14. VENT FAN - circuit breaker applies prime power and provides overload protection for the vent fan. CB5 is a single-phase 2-amp breaker.
15. LIGHTS – circuit breaker applies prime power and provides overload protection for the shelter interior lights. CB4 is a single-phase 5-amp breaker.
16. AMPERES – meter that indicates the input current for each phase.
17. FREQUENCY METER - a reed-type frequency meter that indicates 50/60 Hz line frequency.

18. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)3 POWER UP PROCEDURES
Now lets discuss the Power Up Procedures for the AN/TRC-170 (V)3.
Step
Action
Observation 1
On the Power Entry Panel outside the shelter make sure that the Main Power cable is connected to the Prime AC Power Connector J1 and the system ground connection is made.
Prime power and ground connections are made and securely tighten. 2
Ensure that all of the Air Exhaust and Air Inlet Panels are open.
Air Exhaust and Air Inlet Panels are open. 3
On the Power Entry Panel open the circuit breaker cover and ensure that all the circuit breakers are in the OFF position.
Prime circuit breakers are in the OFF position. 4
Ensure that all circuit breakers on the Power Distribution Panel are in the OFF position.
All circuit breakers on the Power Distribution Panel are in the OFF position. 5
Turn on Prime power at the source. Note the frequency (50, 60,or 400 Hz) of prime power.
Prime Power is on. 6
On the Power Entry Panel, set the Exterior Main circuit breaker to “ON”.
On the Power Distribution Unit, CB Tripped indicator is off.

19. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)3 POWER UP PROCEDURES
Now lets discuss the Power Up Procedures for the AN/TRC-170 (V)3.
Step
Action
Observation 7
Set the Interior Main circuit breaker to the ON position.
Prime power is on in the system.
Note
If blackout condition exists, set Light Intlk Override switch to the Normal position.. The white shelter lights will turn off when the shelter door is opened. 8
Set the Lights circuit breaker to the ON position.
Lights circuit breaker is in the ON position. Ensure that each light switch is pulled out. The shelter lights go on. 9
Set the Light Intlk Override switch to the Override position.
The shelter lights remain on when the door is open. 10
Select Phase Select switch to Phase A.
The Voltmeter indicates 120 ± 12 VAC. The frequency meter indicates 55 ± 7 or 400 ± 20 Hertz. 11
Select Phase Select switch to Phase B.
Same as for phase A, listed in step 10. 12
Select Phase Select switch to Phase C.

20. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)3 POWER UP PROCEDURES
Now lets discuss the Power Up Procedures for the AN/TRC-170 (V)3.
Step
Action
Observation 13
On the DGM Group circuit breaker to ON.
Turn on the DGM equipment and observe the Power Indicators are illuminated. 14
Set the DGM Group circuit breaker to the ON position.
The DGM Equipment indicators are illuminated. 15
Set the LVPS ½ circuit breaker to the ON position.
LVPS Power front panel indicators are illuminated.
Shelter Hour Meter starts operating. A white mark will appear intermittently between the first two meter digits indicating that the meter is operating. The meter will become stabilized within 30 seconds. 16
Set the Fan Pwr Conv (AC-to AC) circuit breaker to the ON position.
AC-to-AC input power indicator is on. You will hear a high pitch noise from the 400 hertz fans that are running. 17
Make sure all air inlet and outlet vents are open on the outside of the shelter.
Normal airflow is present at all the outlets.

21. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)3 POWER UP PROCEDURES
Now lets discuss the Power Up Procedures for the AN/TRC-170 (V)3.
Step
Action
Observation 18
Set the HPA circuit breaker to the ON position.
HPA circuit breaker is in the on position. 19
If the Voice Orderwire Control Unit alarms sounds, depress the SUPPR/TEST push-button.
No alarms heard. 20
If the FAULT-SUMMARY indicator on the Voice Orderwire Control
Indicator goes off. 21
If the remaining circuit breakers the Vent Fan, DLED ½, Shelter Heater, and INTRO ON Outlet are required to be ON. Then proceed by turning them ON.
The circuit breakers are in the ON position.

22. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)3 INPUT AC VOLTAGE DISTRIBUTION
Now lets discuss the AC Voltage Distribution for the AN/TRC-170 (V)3.
Three 3-Phase power is applied to J1 on the Power Entry Panel and filtered by RFI Filter FL1.
The 3-Phase power is then distributed by the Power Distribution Panel.
The AC 3-Phase power is applied to the Low Voltage Power Supplies LVPS 1 & 2.
The 3-Phase power is applied to the AC-to-AC converter
The 3-Phase power is applied to the High Power Amplifier (HPA).
Single phase voltage is applied to the DGM equipment, Shelter lights, Convenience outlets, and the KG-84 DLEDs.

23. Power Entry Panel Voltage & Current Flow for the V2
CECOM LAR Tropo Operation Course
Power Entry Panel Voltage & Current Flow for the V2
Now lets discuss the voltage and current flow for the Power Entry Panel for the AN/TRC-170(V)2 Refer to FO 2-1.
1. Connector J1: accepts 3 Phase Power in and the 3 Phases and Neutral are paralleled with the Surge Protection Fault Assembly.
2. Surge Protection Fault Assembly: When a High Voltage surge occurs the Metal Oxide Arrestors (MOV) will short causing the fuse to blow, and the associated lamp to light. The system will continue to operate but with no protection on that associated phase or Neutral. This item is the same in all models of the TROPO systems.
3. Transformers T1, T2, T3: the inducted input voltage is taken off the main power input via transformer windings T1, T2, and T3. 4. The output of these transformers are sent to RFI filters FL2 through FL5.
4. RFI FL2 through FL5: these RFI filters blocks any RF signals riding on the AC input voltages and neutral. The outputs of these RFI filters is passed to the Power Distribution Assembly monitor metering circuits.
5. RFI Filter FL1: filters Phases A, B, C, & Neutral prior to leaving the Power Entry Panel.
6. The Power Entry Panel: is the very similar for both TROPO systems with the exceptions of the Exterior and ECU circuit breakers to include the ECU power connector on the V2 for a higher current capability. It is located on the Roadside of the shelter.

24. Power Entry Panel Voltage & Current Flow V2 continued
CECOM LAR Tropo Operation Course
Power Entry Panel Voltage & Current Flow V2 continued
Now lets continue our discussion on the Power Entry Panel Refer to FO 2-1
1. Exterior Main Circuit Breaker CB1: this ninety (90) amp circuit breaker receives 3-Phase AC voltages from connector J1. When closed allows all three (3) phases to be applied to the ECU Circuit Breaker CB2.
2. ECU Circuit Breaker CB2: when closed allows all 3-phases to be passed to connector J6 called the ECU power.
3. External (Ext) Convenient (CNVC) Outlet Circuit Breaker CB4: is a fifteen (15) amp circuit breaker. When closed allows Phase A to be passed to connector J7 called CNVC Outlet.
4. ANT ½ Deicing Circuit Breaker CB5: is a five (5) amp circuit breaker. When closed allows Phase B to be passed to connector J8 and J9.

25. Power Entry Panel Controls & Indicators for the (V)2
CECOM LAR Tropo Operation Course
Power Entry Panel Controls & Indicators for the (V)2
Now lets discuss the Power Entry Panel Control & Indicators
1. Exterior Main Circuit Breaker: Applies prime power to the shelter exterior and provides overload protection. CB1 is a 3-phase circuit breaker.
2. ECU connector: power connection for environmental control unit (air conditioner)
3. ANT 1 DEICING connector: for antenna 1 de-icing cable
4. CNVC OUTLET connector: for accessory equipment
5. ANT 2 DEICING connector: connector for antenna 2 de-icing cable
6. PRIME POWER connector: for 208 VAC 3 phase or 400 Hz connector for prime power from external source.
7. CNVC OUTLET Circuit Breaker: applies power to CNVC OUTLET connector and provides overload protection. CB4 is a single-phase 15-amp GFI breaker.
8. ANT 1 / 2 DEICING Circuit Breaker: applies power to DEICING connectors and provides overload protection. CB3 is a single-phase 5-amp breaker.
9. ECU PWR Circuit Breaker: applies power to ECU connector and provides overload protection. CB2 is a 3-phase 35-amp breaker.
10. GROUND terminal lug: external ground terminal connection for shelter ground.

26. Surge Protection Fault Assembly for the (V)2
CECOM LAR Tropo Operation Course
Surge Protection Fault Assembly for the (V)2
Now lets discuss the Surge Protection Fault Assembly in the Power Entry Panel for the AN/TRC-170(V)2 refer to FO 2-1.
1. Surge Protection Fault Assembly: uses metal oxide varistors, one for each phase A, B, C, and neutral.
2. When a high voltage surge has occurred: the MOV will absorb the high voltage surge and it will short circuit to ground , causing the lamp to light alerting the operator that a high voltage surge has shorted the MOV.
Each phase and neutral: has an individual fuse in parallel with the lamps. The surge protection fault assembly is connected in parallel with each input leg and neutral.
The system can continue to operate but with out surge protection. This means that if another high voltage spike occurs on that same leg it may damage the equipment. The Surge Protection Fault Assembly is the same in both the AN/TRC-170(V)2 and AN/TRC-170(V)3 systems.

27. Power Distribution Panel Voltage & Current Flow (V2)
CECOM LAR Tropo Operation Course
Power Distribution Panel Voltage & Current Flow (V2)
Now lets discuss the AC Input Voltage & Current Flow through the Power Distribution Panel Assembly for the (V)2. Please refer to FO 2-4a.
1. Switch S1 Meter Transfer Switch Phase Select: This input power is used by the Phase Select switch S1 and allows monitoring of the current draw for each input phase by ammeter M3. Allows monitoring of the voltage and frequencies of each input phase by voltmeter M4 and frequency meters, M1 for 50/60 hertz and M2 for 400 hertz. Control Circuit Breaker CB13 protects these meters.
2. Control Circuit Breaker CB13: Receives Phase A, B, and C from the Power Entry Panel. Must be activated for the TROPO system to power up. Applies power to the Over/Under Voltage Relay K1 and Phase Select Switch 1. Provides protection for the meters M1 through M4 and Switch S1. If this circuit breaker opens, it will illuminate the Control CB Tripped Lamp DS1 on the Power Distribution Panel. This Control Circuit Breaker CB13 is on the inside of the Power Distribution panel along with fuse F1.
3. Over/Under Voltage Relay K1: The K1 Relay monitors the Voltage & Frequency of the input power. The voltage from each leg to neutral is 120 VAC  10 %. Should any phase exceed 140 VAC or be less than 100 VAC, a sensor circuit in the Over/Under voltage relay will cause K1 to denergize causing the Interior Main Prime Power Circuit Breaker CB1 contacts to open removing power from all units in the shelter. Also, a five (5) volt difference between any two phases will cause K1 to denerigize causing CB1 contacts to open removing power from the shelter.

28. Power Distribution Panel Voltage & Current Flow (V2) continued
CECOM LAR Tropo Operation Course
Power Distribution Panel Voltage & Current Flow (V2) continued
Now lets continue the discussion the AC Input Voltage & Current Flow through the Power Distribution Panel Assembly for the (V)2. Please refer to FO 2-4a.
1. Interior Main Prime Power Interrupt Circuit Breaker CB1: Next the AC Power comes to the Interior Main Prime Power Circuit Breaker. This circuit breaker is a 3-phase 90-amp circuit breaker. Power is then applied to all the other circuit breakers on the Power Distribution Panel Assembly. If voltage is removed from the coil of this circuit breaker it will cause this circuit breaker to open removing power from inside the shelter.
2. Circuit Breakers CB2 and CB3: these circuit breaker are a 3-phase 30 amp circuit breaker that when closed provides 3-phase power to the High Power Amplifiers (HPA).
Circuit Breaker CB2 powers HPA 1 and Circuit Breaker CB3 powers HPA 2.
3. Circuit Breaker CB11: this circuit breaker is a 3-phase 10 amp circuit breaker that when closed provides 3-phase power to the Fan Power Converter 2 (AC-to-AC Converter # 2).

29. Power Distribution Panel Voltage & Current Flow (V2) continued
CECOM LAR Tropo Operation Course
Power Distribution Panel Voltage & Current Flow (V2) continued
Now lets continue to discuss the AC Input Voltage & Current Flow through the Power Distribution Panel Assembly for the (V)2. Please refer to FO 2-4b.
Fan Power Converter (AC-to-AC Converter 1) Circuit Breaker CB10: this circuit breaker is a 3-phase 10-amp circuit breaker. When closed allows 3-phase power to be applied to AC-to- AC converter#1 assembly.
2. Circuit Breaker CB9: this circuit breaker is a 3-phase 20-amp circuit breaker. When closed allows 3-phase power to be applied to the shelter heater assembly.
3. Circuit Breaker CB8: this circuit breaker is a 3-phase 10-amp circuit breaker. When closed allows 3-phase power to be applied to both of the Low Voltage Power Supplies LVPS-1 and LVPS-2.
4. Circuit Breakers CB8 & CB9: both these circuit breakers can be tripped if the coil is energized by the +28vdc that is applied through Thermal Switch S1 in the Road Side Air Duct Assembly (4A4) and Curb Side Air Duct Assembly (7A5). If the temperate reaches 150 degrees Fahrenheit the contacts in the Thermal Switch will close, applying +28vdc to the coils of these circuit breaker CB8 and CB9, causing these circuit breakers to open. The circuit breakers that are affected by this circuitry are; the DGM Group, DLED1/ 2, LVPS 1/ 2, and the Shelter Heater.

30. Power Distribution Panel Voltage & Current Flow (V2) continued
CECOM LAR Tropo Operation Course
Power Distribution Panel Voltage & Current Flow (V2) continued
Now lets continue to discuss the AC Input Voltage & Current Flow through the Power Distribution Panel Assembly for the (V)2. Please refer to FO 2-4c.
1. Circuit Breaker CB6 DGM Equipment: this circuit breaker is a single phase 10-amp circuit breaker. When closed allows voltage to be applied to the DGM equipment.
2. Circuit Breaker CB7 DLED 1 & 2: this circuit breaker is a single phase 2-amp circuit breaker. When closed allows voltage to be applied to the KG-84 DLEDs 1 & 2.
3. Circuit Breaker CB12 CNVC Outlets: this circuit breaker is single phase 15-amp circuit breaker. When closed allows voltage to be applied to the convenience outlets.
4. Circuit Breaker CB5 Vent Fan: this circuit breaker is single phase 2-amp circuit breaker. When closed allows voltage to be applied to the Vent fan.
5. Circuit Breaker CB4 Lights: this circuit breaker is single phase 5-amp circuit breaker. When closed allows voltage to be applied to the shelter lights.
6. Circuit Breakers CB6 & CB7: both these circuit breakers can be tripped if the coil is energized by the +28vdc that is applied through Thermal Switch S1 in the Road Side Air Duct Assembly (4A4) and Curb Side Air Duct Assembly (7A5). If the temperate reaches 150 degrees Fahrenheit the contacts in the Thermal Switch will close, applying +28vdc to the coils of these circuit breaker CB6 and CB7, causing these circuit breakers to open. The circuit breakers that are affected by this circuitry are; the DGM Group, DLED1/ 2, LVPS 1/ 2, and the Shelter Heater.

31. Power Distribution Panel Controls and Indicators (V2)
CECOM LAR Tropo Operation Course
Power Distribution Panel Controls and Indicators (V2)
Now lets discuss the Power Distribution Panel Assembly Control and Indicators for the (V)2.
INTERIOR MAIN - prime power circuit breaker applies prime input power to shelter equipment and provides overload protection. CB1 is a 3-phase 90-amp breaker.
HPA # 1 - circuit breaker applies prime power to the High Power Amplifier (HPA #1) and provides over­ load protection. CB2 is a 3-phase 30 amp breakers.
HPA # 2 - circuit breaker applies prime to the High Power Amplifier (HPA # 2) and provides over­ load protection. CB3 is a 3-phase 30 amp breakers.
CONTROL CB TRIPPED - indicator lamp (red) indicates control circuit breaker is open.
FREQUENCY METER - a reed-type frequency meter that indicates 400 Hz line frequency.
PHASE SELECT – switch that selects phase A, B, or C of primary power to be monitored by meter.
VOLTS – meter that indicates the voltage of phase A, B, C of primary power.
LIGHT INTLK OVERRIDE - NORMAL switch in the OVERRIDE position, the shelter interior lights remain on when door is opened. In NORMAL position, the shelter interior lights turn off when door is opened. and red blackout) light comes on.
DGM GROUP - circuit breaker that applies prime power to LGM 1, GM, TGM, and LGM-2 or LSCDM and provides overload protection. CB6 is a single-phase 10-amp breaker.

32. Power Distribution Panel Controls and Indicators (V2)
CECOM LAR Tropo Operation Course
Power Distribution Panel Controls and Indicators (V2)
Now lets continue the discussion the Power Distribution Panel Assembly Control and Indicators for the (V)2.
10. DLED 1/2 - circuit breaker applies prime power to DLED 1 and 2 and provides overload protection. CB7 is single-phase 2-amp breaker.
11. SHELTER HEATER - circuit breaker applies prime power to shelter heaters and provides overload protection. CB9 is a 3-phase 20-amp breaker.
12. INTR CNVC OUTLET - circuit breaker applies prime power to convenience outlets in shelter and provides overload protection. CB12 is a single-phase 15-amp breaker.
13. FAN PWR CONV 1 - circuit breaker applies prime power to AC-to-AC CONV 1 and provides over­load protection. CB10 is a 3-phase 10 amp breaker.
14. FAN PWR CONV 2 - circuit breaker applies prime power to AC-to-AC CONV 2 and provides over­load protection. CB11 is a 3-phase 10 amp breaker.
15. LVPS 1 / 2 - circuit breaker applies prime power and provides overload protection for both LVPS. CB8 is a 3-phase 10-amp breaker.
16. VENT FAN - circuit breaker applies prime power and provides overload protection for vent fan. CB5 is a single-phase 2-amp breaker.

33. Power Distribution Panel Controls and Indicators (V2)
CECOM LAR Tropo Operation Course
Power Distribution Panel Controls and Indicators (V2)
Now lets continue the discussion the Power Distribution Panel Assembly Control and Indicators for the (V)2.
17. LIGHTS – circuit breaker applies prime power and provides overload protection for shelter interior lights. CB5 is a single-phase 5-amp breaker.
18. AMPERES – meter that indicates the input current for each phase.
19. FREQUENCY METER - a reed-type frequency meter that indicates 50/60 Hz line frequency.
20. SHELTER HOURS METER - that provides accurate shelter operating time. Activated when the LVPS Circuit breaker is turned on and +28 VDC is applied from LVPS #1.

34. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)2 POWER UP PROCEDURES
Now lets discuss the Power Up Procedures for the AN/TRC-170 (V)2.
Step
Action
Observation 1
On the Power Entry Panel outside the shelter make sure that the Main Power cable is connected to the Prime AC Power Connector J1 and the system ground connection is made.
Prime power and ground connections are made and securely tighten. 2
Ensure that all of the Air Exhaust and Air Inlet Panels are open.
Air Exhaust and Air Inlet Panels are open. 3
On the Power Entry Panel open the circuit breaker cover and ensure that all the circuit breakers are in the OFF position.
Prime circuit breakers are in the OFF position. 4
Ensure that all circuit breakers on the Power Distribution Panel are in the OFF position.
All circuit breakers on the Power Distribution Panel are in the OFF position. 5
Turn on Prime power at the source. Note the frequency (50, 60,or 400 Hz) of prime power.
Prime Power is on. 6
On the Power Entry Panel, set the Exterior Main circuit breaker to “ON”.
On the Power Distribution Unit, CB Tripped indicator is off.

35. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)2 POWER UP PROCEDURES CONTINUED
Now lets continue out discussion the Power Up Procedures for the AN/TRC-170 (V)2.
Step
Action
Observation 10
Set the Phase Select Switch to Phase A.
The Voltmeter indicates 120 ± 12 VAC. The frequency meter indicates 55 ± 7 or 400 ± 20 Hertz. 11
Set the Phase Select Switch to Phase B.
Same as for Phase A, listed in step 10. 12
Set the Phase Select Switch to Phase C. 13
Set the DGM equipment circuit breakers to the ON position. 14
Set the DGM Group circuit breaker to the ON position.
The DGM equipment indicators are illuminated. 15
Set the LVPS ½ circuit breaker to the ON position.
LVPS Power front panel indicators are illuminated.
Shelter Hour Meter starts operating. A white mark will appear intermittently between the first two meter digits indicating that the meter is operating. The meter will become stabilized within 30 seconds.

36. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)2 POWER UP PROCEDURES CONTINUED
Now lets continue out discussion the Power Up Procedures for the AN/TRC-170 (V)2.
Step
Action
Observation 16
Set the FAN PWR CONV 2 (AC-to AC # 2) circuit breaker to the ON position.
AC-to-AC Converter # 2 input power indicator is on. You will hear a high pitch noise from the 400 hertz fans that are running. 17
Set the FAN PWR CONV 1 (AC-to AC # 1) circuit breaker to the ON position.
AC-to-AC Converter # 1 input power indicator is on. You will hear a high pitch noise from the 400 hertz fans that are running. 18
Make sure all air inlet and outlets vents are open on the outside of the shelter.
Normal airflow is present at all the outlets. 19
Set the HPA 1 circuit breaker to the ON position.
HPA 1 circuit breaker 1 is in the ON position. 20
Set the HPA 2 circuit breaker to the ON position.
HPA 1 circuit breaker 2 is in the ON position. 21
If the Voice Orderwire Control Unit alarm sounds, depress the SUPPR/TEST push-button.

37. CECOM LAR Tropo Operation Course
AN/TRC-170 (V)2 POWER UP PROCEDURES CONTINUED
Now lets continue out discussion the Power Up Procedures for the AN/TRC-170 (V)2.
Step
Action
Observation 22
If the FAULT-SUMMARY indicator on the Voice Orderwire Control Unit is on, press the FAULT-RESET switch.
Indicator goes off. 23
If the remaining circuit breakers the Vent Fan, DLED ½, Shelter Heater, and CONV INTR Outlets are required to be ON. Then proceed by turning them ON.
The circuit breakers are in the on position.

38. CECOM LAR Tropo Operation Course
AN/TRC-170(V)2 Input AC Voltage Distribution
Now lets discuss the AC Voltage Distribution for the AN/TRC-170 (V)2.
Three 3-Phase power is applied to J1 on the Power Entry Panel and filtered by RFI Filter FL1.
The 3-Phase power is then distributed by the Power Distribution Panel.
The AC 3-Phase power is applied to the Low Voltage Power Supplies LVPS 1 & 2.
The 3-Phase power is applied to both the AC-to-AC converters
The 3-Phase power is applied to both High Power Amplifiers (HPAs).
Single phase voltage is applied to the DGM equipment, Shelter lights, Convenience outlets, and the KG-84 DLEDs.

39. CECOM LAR Tropo Operation Course
AN/TRC-170 System Grounding
Now lets discuss AN/TRC-170 System Grounding.
1. GROUNDING: The TROPO system must be grounded in 3 places:
(1). The generator or the power source
(2) The shelter power entry panel
(3) At both signal entry panels.
2. GROUND SYSTEM: A very important part of setting up the shelter is the installation of these grounds. Bad grounds are one of the most common causes of poor tactical communications. A suitable ground system is needed to provide personnel safety, equipment protection, and electrical noise reduction. A low resistance ground cable attached to the equipment provides personnel safety and equipment protection. Electrical noise reduction is accomplished on communications circuits by ensuring the resistance to earth ground is minimal between signal ground points throughout the communication facility. These ground points prevent noise sources within the van from radiating the noise to the communication circuits.
3. FACTORS: factors that may affect resistance in ground are temperature, amount of moisture in soil, mineral content, and topsoil thickness. The most common ways to improve a ground system is to use larger ground rods in diameter and length. Drive the ground rods deeper than usual.

40. CECOM LAR Tropo Operation Course
AN/TRC-170 Air Duct Thermal Switch Circuitry
Now lets discuss the AN/TRC-170 System Air Duct Thermal Switch Circuitry.
Both of the AN/TRC-170(V)2 and the AN/TRC-170(V)3 systems Air Duct Assemblies utilize a Thermal Switch to detect temperature.
The Thermal Switch S1 contacts close when the temperature reaches 150 degrees Fahrenheit, which allows +28vdc to be applied to the coils of Circuit Breakers CB6 through CB9. The +28vdc will then cause these circuit breakers to open.
The circuit breakers that are affected by this circuitry are; the DGM Group, DLED1/ 2, LVPS 1/ 2, and the Shelter Heater. The temperature has to drop to 146 degrees before the Thermal Switch S1 contacts open again.
This circuitry is designed to prevent damage to the equipment when the Air Duct Assembly temperate reaches 150 degrees Fahrenheit.
The one Air Duct Assembly in the AN/TRC-170(V)2 is the 2A1 assembly.
The two Air Duct Assemblies in the AN/TRC-170(V)3 are the Roadside 4A4 and Curbside 7A5 assemblies.

41. CECOM LAR Tropo Operation Course
AC-to-AC Converter
Now lets discuss the purpose of the AC-to AC Converters utilized in both AN/TRC-170 Systems.
1. PURPOSE: The function of the AC-AC Converter is to convert 50, 60, and 400 Hz prime power to a 400 HZ, 255 volts 3-phase (quasi-square wave) for the purpose of driving the 400 HZ fans in the Transmit Modem, Receive Modem, Upconverter, Shelter Rack, and the High Power Amplifier (Klystron and unit fans to include the FAINT, and the three Inverters).
2. The AN/TRC-170(V)3 contains only one AC-to-AC Converter (7A4).
3. The AN/TRC-170(V)2 contains two AC-to-AC Converters. The AC-to-AC Converter (6A7) only powers the fans in High Power Amplifier number 2.
4. The AC-to-AC Converter (7A7) powers the fans in the High Power Amplifier number 1, Upconverters 1 and 2, Transmit Modem, Receive Modem, and Shelter Air Duct Assembly. In the AN/TRC-170(V)3 the AC-to-AC Converter powers all the equipment fans.

42. CECOM LAR Tropo Operation Course
AC-to-AC Converter Specifications
Now lets discuss the Specification od AC-to AC Converters utilized in both AN/TRC-170 Systems.
INPUT AC POWER VACFrequency50/60/400Phase
Three (3) Outputs – Three Phase Power at AC Power255 VAC at a frequency of 400 Hertz.
Fault Monitor Signal - DC voltage logic signal as a Summary Fault. This fault is displayed on the Alarm Monitor Unit as a LVPS fault.

43. CECOM LAR Tropo Operation Course
AC-to-AC Converter Voltage & Current Flow continued
Now lets discuss the functional operation of the AC-to AC Converters utilized in both AN/TRC-170 Systems. Refer to Fold Out FO 2-6.
1. A3 Power Inverter Assembly: The 115 VAC 3-phase, 50/60/400 Hertz input power is first applied to the A3 Power Inverter Assembly. This 3-phase 115 VAC is applied to a 3-phase bridge rectifier circuit consisting of diodes CR1 through CR6. The +28 VDC input from the Low Voltage Power Supply (LVPS) is applied to a +24 VDC regulator on the A3 and then distributed throughout the AC-to-AC Converter.
2. A2 Fault Detector Circuit Card: Receives the +24 VDC from the A3 Power Inverter Assembly and sends this voltage to the A1 Driver Circuit Card.
3. A1 Driver Circuit Card: The +24 VDC from the A2 Fault Detector Circuit Card is applied to a +12 VDC regulator on the A1 Driver CCA. This +12 VDC is then applied to the start the Clock Generator circuitry. The three outputs of the clock generator circuitry is applied to the trigger timing circuitry, the output of the Trigger Timing circuitry is applied to the Trigger Driver circuitry. The three triggers A, B, and C outputs are then sent to the A3 Power Inverter Assembly. If the A2 Fault Detector CCA detects a fault, it sends a signal to the Trigger Inhibit gates, blocking the Timing Triggers from feeding the Trigger Driver circuitry.

44. CECOM LAR Tropo Operation Course
AC-to-AC Converter Voltage & Current Flow
Now lets continue our discussion of the functional operation of the AC-to AC Converters utilized in both AN/TRC-170 Systems. Refer to Fold Out FO 2-6
4. A3 Power Inverter Assembly: The Trigger Inputs A, B, and C are received from A1 Driver CCA. These Trigger inputs are used as inputs to the power transistors Q1 through Q6. The switching of these transistors generates the AC output at a frequency of 400 hertz. The output of these transistors is then sent to Transformer T2. Fuse F1 is mounted on this assembly and limits the amount of current that is drawn on the output voltages that power the fan assemblies within the TROPO system.
5. T2 Transformer Assembly: The 255 VAC 3-phase 400 hertz output from the A3 Power Inverter Assembly is received by Transformer T2. This transformer is used to increase the current on the secondary output to the load. It also matches the impedance in order to transfer energy from the source to the load. The output of this transformer is then sent to output connectors J2 and J3. Also, samples of the three-phase output are then sent to the A2 Fault Detector Circuit Card.

45. CECOM LAR Tropo Operation Course
AC-to-AC Converter Voltage & Current Flow
Now lets finish our discussion of the functional operation of the AC-to AC Converters utilized in both AN/TRC-170 Systems. Refer to Fold Out FO 2-6
6. A2 Fault Detector Circuit Card - Receives the three sample Inverter outputs and analyzes that the output voltages are correct and present. If one or more of the output voltages are missing or low in amplitude, then a fault signal is generated. This fault signal will then illuminate LED DS2 the Output Fault on the front panel and the Summary Fault signal is sent to the Alarm Monitor Unit and displayed as a LVPS fault. It also monitors the +280VDC to ensure that an over voltage condition does not occur, if an over voltage condition occurs then an inhibit signal is sent to the A4 Resistor Step-Start Circuit Card.
7. A4 Resistor Step-Start Circuit Card - If a fault is detected as an input from the A2 Fault Detector Circuit Card it then sends a signal to the A5 Resistor Step-Start Circuit Card causing the relays on the A5 CCA to open stopping current flow.
8. A5 Resistor Step-Start Circuit Card - This CCA limits the current flow on the initial turn on. It also controls current flow through relays K1 and K2.

46. CECOM LAR Tropo Operation Course
AC-to-AC Converter Output Distribution for the AN/TRC-170(V)3
Now lets discuss the 255 VAC 3-phase 400 Hz Output Distribution of the AC-to-AC converter for the AN/TRC-170(V)3 system. Refer to Figure 2-7
1. In the AN/TRC-170(V)3 the AC to AC Converter (7A4) outputs are coupled to the RF Amplifier HPA via connector J2 on the back of the AC-to-AC converter.
2. Connector J3 - also provides an output to the AC Distribution Panel Unit 13 where it is the distributed to the Upconveter (3A1), TROPO Transmit Modem (4A1), TROPO Receive Modem (4A2), Air Duct Assembly Curb Side (7A5), and the Air Duct Assembly Road Side (4A4).
3. The HPA has six (6) fans – HPA
Klystron
Faint Assy
Inverter A
Inverter B
Inverter C

47. CECOM LAR Tropo Operation Course
AC-to-AC Converter # 1 Output Distribution for the AN/TRC-170(V)2
Now lets discuss the 255 VAC 3-phase 400 Hz Output Distribution of the AC-to-AC Converter # 1 for the AN/TRC-170(V)2 system. Refer to Figure 2-8.
1. In the AN/TRC-170(V)3 the AC to AC Converter (7A4) outputs are coupled to the RF Amplifier HPA via connector J2 on the back of the AC-to-AC converter.
2. Connector J3 also provides an output to the AC Distribution Panel Unit 13 where it is the distributed to the Upconveter (3A1), TROPO Transmit Modem (4A1), TROPO Receive Modem (4A2), Air Duct Assembly Curb Side (7A5), and the Air Duct Assembly Road Side (4A4).

48. CECOM LAR Tropo Operation Course
AC-to-AC Converter # 2 Output Distribution for the AN/TRC-170(V)2
Now lets discuss the 255 VAC 3-phase 400 Hz Output Distribution of the AC-to-AC Converter # 2 for the AN/TRC-170(V)2 system. Refer to Figure 2-9.
In the AN/TRC-170(V)2 the AC to AC Converter (7A4) outputs - are coupled to the RF Amplifier HPA via connector J2 on the back of the AC-to-AC converter.
The HPA has six (6) fans – HPA
Klystron
Faint Assy
Inverter A
Inverter B
Inverter C

49. CECOM LAR Tropo Operation Course
AC-to-AC Converter Front Panel Indicators and Circuit Cards
Now lets discuss the AC-to-AC Converter Front Panel Indicators and Circuit Cards.
OUTPUT FAULT LED (red) - indicates an under voltage or over current condition.
INPUT POWER LED (green) - indicates the +28 VDC input is applied from the Low Voltage Power Supply.
208V ON LED (green) - indicates the 208V is present at the power supply on the A3 Power Inverter Assembly.
A1 Driver CCA - has three green LEDs that indicate that the trigger drive signal is present for each of the three output phases. Normal indication is that the LEDs are on.
A2 Fault Detector CCA - has one red LED which illuminates when any one of the internal circuits are faulty.

50. CECOM LAR Tropo Operation Course
AC-to-AC Converter A3 Power Inverter Module & Fuse F1 location
Now lets discuss the AC-to-AC Converter A3 Power Inverter Module & Fuse F1 location
A3 Power Inverter Module – is located on the back side of the AC-to-AC converter. It Provides 255 VAC, 3-Phase 400 Hertz, Output Power for the TROPO fans.
Fuse, F1 - is a 15 amps for protection of the A3 Power Inverter Module. This Fuse, F1 is mounted on this module.