MH-60R - Systems - Electrical Flashcards
(14 cards)
Describe the AC generators.
Primary ac electrical power is supplied by two oil-cooled 30/45-kVA, 115-volt ac, 3-phase, 400-Hz generators driven by the transmission accessory modules. The generators are lubricated by the main transmission lubricating system. Secondary ac electrical power is supplied by an air-cooled 35-kVA, 115-volt ac, 3-phase, 400-Hz generator driven by the APU. A Generator Control Unit (GCU) connects each respective generator to the ac electrical bus system, regulates generator output, and protects system components and circuitry against overvoltage, undervoltage, feeder fault, and underfrequency.
Describe the Electrical system.
Alternating Current (ac) is the primary source of electrical power and can be supplied from the main generators, the APU generator, or external power. The primary source of ac power is the two main generators driven by the transmission. A secondary source of ac power is the APU-driven generator. External ac power can also be connected to the helicopter on the ground. Dc electrical power is supplied by two converters that convert 115-volt ac power to 28-volt dc power. A 24-volt dc Nickel-Cadmium (NICAD) battery is installed primarily to start the APU and power the Battery Utility bus. Ac and dc power is distributed to individual components by a bus distribution system.
Describe the external power receptacle.
The external power receptacle provides a connection to energize the entire electrical system when it is the sole source of power. External power is monitored for phase rotation, overvoltage, undervoltage, underfrequency, and overfrequency. The external power system includes a 4-amp circuit breaker that places a 2-amp draw on the power cable when connected to the aircraft. Some shipboard power systems require a load to be sensed in order to apply power to the cable.
What are the 2 notes associated with the AC generators?
Should the main rotor system droop below 94 percent Nr on the ground, the GCU, via an input from the WOW switch, removes the main generator electrical input from the entire ac power distribution system.
In flight, underfrequency protection is disabled and the generators will remain online until the Nr decreases to approximately 80 percent. A minimum of 97 percent Nr is required for the GCU to reconnect the No. 1 and No. 2 generators to the ac electrical distribution system.
What are the 5 buses for the AC distribution system called?
the No. 1 and No. 2 AC Primary buses (#1/2 AC PRI BUS), the AC Essential bus (AC ESNTL BUS), the ac Secondary bus (AC SEC BUS), and the ac Monitor bus (AC MON BUS).
How is AC power distributed?
With both main generators operating normally, the No. 1 generator powers the No. 1 AC Primary, ac Essential, and ac Secondary buses; the No. 2 AC generator powers the No. 2 AC Primary and the ac Monitor bus. If the APU generator is selected while both main generators are operating, the APU generator will not be connected to the ac bus distribution system. Should either main generator fail, automatic bus switching limits the ac load to the available generator output.
If electrical power demand exceeds the capacity of the generator operating normally, in what order are the electrical bus loads redistributed to available generators?
- The backup hydraulic pump (major load on the No. 1 AC Primary bus) will always be powered, if required.
- The mission avionics system is the major load on the AC Secondary bus and is the next priority. Tail rotor deice power is also supplied from this bus.
- The main rotor deice system is the only system powered from the AC Monitor bus and has the lowest priority of the major current-drawing components
What do the different Generator switch positions do?
Cockpit switches that control the main generators, APU generator, and external power are located on the upper console. The three-position No. 1, No. 2, and APU GENERATOR switches labeled ON, OFF/RESET, and TEST function as follows:
- ON — connects the respective generator ac output to the ac power distribution system.
- OFF/RESET — disconnects the generator from the ac power distribution system and resets the GCU if it was either disabled or disconnected from the ac power distribution system.
- TEST — tests the generator ac output without connecting it to the ac distribution system.
What do the different positions on the EXTPWR switch do?
- ON — connects external ac power to the ac bus distribution system.
- OFF — disconnects external ac power from the distribution system.
- RESET — recycles the ac external power source if the external power monitor removed power due to an unacceptable parameter.
When do the #1/#2 GEN cautions appear?
- Respective generator is not supplying power to the buses.
- Respective generator is selected off.
- A failure of the generator, GCU, contactor control relay, or wiring fault has occurred.
When do the #1/#2 GEN BRG cautions appear?
The #1/#2 GEN BRG caution appears when the generator main bearing is worn or has failed.
When do the APU GEN cuations appear?
The APU GEN ON advisory indicates the generator is supplying electrical power to a primary ac bus. The APU GEN caution appears under the following conditions:
- Failure of the APU-driven generator, GCU, contactor control relay, or wiring fault.
- APU generator selected ON, APU started, but has not reached operating limits.
Describe the DC Electrical system.
Two converters supply 28-volt dc power. The converters are powered by the No. 1 and No. 2 AC Primary buses, respectively. A 24-volt dc battery, located in the copilot seat well, is the primary source of power for APU starting and the secondary source of power for the dc essential bus and the Battery bus. With an 80 percent charge, normal battery life is 11 minutes for day operations and 9 minutes for night operations.
How does the BAC work?
A battery analyzer/conditioner, also located in the copilot seat well, monitors the battery system for fault conditions, battery charge, internal temperature, cell conditions, and provides a battery-charging capability. If the analyzer/conditioner senses a fault, it will automatically disconnect the dc loads from the battery, or the battery from the charging circuit, as appropriate. When the converters are operating and the BATT switch is ON, the charging circuit of the analyzer/conditioner receives power from the No. 2 AC Primary bus and dc charging power from the No. 2 DC Primary bus.
