(3)
Electrical Connection Diagram- Interconnecting wiring harnesses are color-coded to aid the mechanic.
(a)
The yellow harness connects circuits that are dedicated solely to "engine electrical functions".
(b)
The blue harness is dedicated to the "Np Overspeed and torque indication systems".
(c)
The green harness functions as an "engine to airframe interface".
(d)
The black harness is dedicated to "engine ignition".
b.
Engine Alternator- The engine-supplied electrical alternator is mounted on the forward face of the Accessory Gearbox (AGB), on the right-hand side. It supplies AC power to the ignition exciter, Electrical Control Unit (ECU), and supplies an Ng speed signal to the cockpit. The alternator powers all essential engine functions. The alternator rotor is mounted on a cantilevered shaft extending from the gearbox. The rotor contains a set of 12 permanent magnets. The stator housing encloses the rotor and is bolted to the gearbox case. It contains three separate sets of windings for its three functions: Ignition power, ECU power, and Ng signal.
(1)
A Gas Generator Ng speed signal originates at the alternator and is forwarded to the CDU through the SDC. When the Ng VID on the CDU indicates 55 % Ng speed, the ENGINE OUT warning light illuminates and the audio warning is also activated. Failure of the Ng winding in the alternator causes a false ENGINE OUT indication, always cross check RPM R and TGT to verify the ENGINE OUT warning.
(2)
A dual ignition exciter (5000 to 7000 volts) is mounted on the right side of the engine, and powers the two igniter plugs. The engine alternator supplies power for the engine ignition. The ignition is activated when three conditions are met: the key is on, the start relay is energized, and the alternator is supplying power (the AGB is being motored by the pneumatic starter). Ignition is only required to light off the fuel air mixture in the combustion chamber and deactivates when the starter caution light goes out. Failure of the ignition winding on the alternator would prevent any further start attempts on that engine.
(3)
The alternator is the primary power source for all ECU functions, although some ECU functions can receive power from airframe sources. When alternator power is removed from the ECU through an alternator failure/loss of rotation, indications of TRQ and % RPM 1 or 2 is lost, and the CDU Ng indication is lost, triggering the ENGINE OUT warning system. The absence of an ECU input to the HMU results in the reset of engine power to maximum (a high side failure), and the TGT indication rises (possibly above limits).
Alternator Functions and Schematic Diagram
c. Electrical Control Unit- The ECU is mounted below the compressor casing with a heat sink projecting into the collection scroll where it's cooled by the dirty air flow. The ECU functions primarily as an electronic engine governor. The ECU has 7 functions. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：UH-60A STUDENT HANDOUT UH-60A T700 ENGINE(24)
