This chapter contains information on DC Generation, External Power, and Electrical Load Distribution.

Transcription

1 CIRRUS AIRPLANE MAINTENANCE MANUAL Electrical Power CHAPTER 24-00: ELECTRICAL POWER GENERAL 24-00: ELECTRICAL POWER 1. General This chapter contains information on DC Generation, External Power, and Electrical Load Distribution. The airplane is equipped with a two-alternator, two-battery, 28-volt direct current (VDC) electrical system designed to reduce the risk of electrical system faults. The system provides uninterrupted power for avionics, flight instrumentation, lighting, and other electrically operated and controlled systems during normal operation. The electrical system also provides automatic switching from either battery or alternator to the Essential Bus in the event of an electrical system failure by the opposing alternator or battery. The bolster panel contains the pilot switches for operating ALT 1, ALT 2, BAT 1, and BAT 2. The switches are mounted adjoining so that a pilot can control all four switches with a single hand. Power generated from the alternators is fed into the Master Control Unit (MCU). The MCU regulates and distributes the power to the batteries and the system loads. Each alternator provides constant charging current for the corresponding battery and primary power to the aircraft electrical system during normal system operation. (See Figure ) A. Electrical Power Alternator 1 (ALT 1) is a gear-driven, internally rectified, 100-amp alternator mounted on the right front of the engine. Alternator 2 (ALT 2) is a 70-amp belt-driven alternator mounted to the left front of the engine. ALT 1 is regulated to 28 volts and ALT 2 is regulated to volts. Both alternators are self-exciting (not self-starting) and require battery voltage for field excitation in order to start up. Battery 1 (BAT 1) is an aviation grade 12-cell, lead-acid, 24-volt, 11-amp-hour battery mounted on the right firewall. BAT 1 is charged from the Main Distribution Bus in the MCU. Battery 2 (BAT 2), located in the empennage, is composed of two 12-volt, 7-amp-hour, sealed, lead-acid batteries connected in series to provide 24 volts. BAT 2 is charged from the circuit breaker panel Essential Bus. 1

2 CHAPTER 24-00: ELECTRICAL POWER 2. Troubleshooting CIRRUS AIRPLANE MAINTENANCE MANUAL No alternator output. (Voltmeter Indicates 24 VDC or less and the ammeter indicates a discharge when the corresponding BAT switch is set to ON position) Loose alternator wire connection. Alternator switch off. Defective alternator. Circuit breaker activated (open). Faulty field control module. Low engine RPM. Tighten connector. Turn on corresponding alternator switch. Reset circuit breaker and troubleshoot circuit. Replace field control module. Increase engine RPM. Alternator output is low. Loose alternator wire connection. Tighten corresponding connector. Faulty field control module. Faulty MCU. Faulty alternator. Low engine RPM. Replace field control module. Increase engine RPM. No battery output. Poor battery connections. Clean and tighten connections. Faulty battery. Replace corresponding battery. Battery will not hold charge. Flights too short to recharge sufficiently. Remove corresponding battery and recharge when necessary. Loose connections, corrosion. Faulty battery. Standing too long (hot climate). Tighten, clean, and neutralize connections. Replace corresponding battery. Remove corresponding battery and recharge when necessary. Short battery life (Battery 1). Battery hold down loose. Keep hold down secure at all times. Overcharging of battery (faulty field control module). 2

3 CIRRUS AIRPLANE MAINTENANCE MANUAL CHAPTER 24-00: ELECTRICAL POWER External power receptacle inoperable. Low volts light illuminates. BAT 1 switch in OFF position. Faulty ground wire/connection. Faulty ground power relay. High demand on electrical system with a low engine RPM setting. Faulty logic module or current sensor. Inspect and repair ground wire/connection at receptacle or firewall ground bus bar. Increase engine RPM or load shed. Alternator is noisy. Worn alternator bearings. Replace corresponding alternator. Faulty alternator diode(s). Replace corresponding alternator. No output from alternator 2. Loose alternator wire connection. Tighten connector. Faulty alternator drive unit. Faulty alternator. Replace alternator drive unit. Alternator 2 output is low. Loose alternator wire connection. Tighten connector. Faulty rectifier. Faulty MCU. Low RPM. Increase RPM. Oil leaks from alternator 2. Faulty oil seal in alternator. Starter motor will not engage. STARTER circuit breaker open. Reset STARTER circuit breaker. If STARTER circuit breaker opens on second attempt, check for wiring short between circuit breaker panel and MCU. Loose electrical connections between MCU and starter motor. Ensure all electrical connections to starter motor are secure. 3

4 CHAPTER 24-00: ELECTRICAL POWER CIRRUS AIRPLANE MAINTENANCE MANUAL Starter motor will not engage. (continued) Starter motor engages when BAT 1 switch is set to ON position. Annunciation for ALT 1 shows steady illumination above 2200 RPM. Starter motor power relay faulty. Starter motor faulty. MCU starter relay welded closed. Starter motor faulty. ALT 1 circuit breaker open. ALT 1 switch faulty. MCU field control module faulty. Alternator 1 faulty. Remove positive cable from starter motor. Connect voltmeter to positive starter motor stud and ground. Set ignition switch to START. Verify volt meter indicates 24 volts. If system voltage reads zero, MCU starter relay faulty. Return MCU to approved factory service center for service. If system voltage reads 24 volts, replace positive terminal on starter motor and attempt to start airplane. If starter motor still does not engage, replace starter motor. (Refer to 80-10) Replace starter motor. (Refer to 80-10) MCU starter relay faulty. Return MCU to approved factory service center for service. Replace starter motor. (Refer to 80-10) Reset ALT 1 circuit breaker. Test ALT 1 switch and relay: Measure voltage between pin K of P183 and ground. If voltage does not measure volts, replace bolster switch panel. At alternator 1 with alternator cables attached, measure voltage between field input and ground. If voltage does not measure volts, replace MCU field control module. (Refer to 24-30) At alternator 1, measure resistance between field connector and ground. If resistance shows open circuit, alternator coil is damaged. Repair or replace alternator 1. (Refer to 24-30) 4

5 CIRRUS AIRPLANE MAINTENANCE MANUAL CHAPTER 24-00: ELECTRICAL POWER Annunciation for ALT 2 shows steady illumination above 2200 RPM. ALT 2 circuit breaker open. ALT 2 switch faulty. Reset ALT 2 circuit breaker. Test ALT 2 switch and relay: Measure voltage between pin K of P182 and ground. If voltage does not measure volts, replace bolster switch panel. ALT 2 field control module faulty. At alternator 2, disconnect J125. Measure voltage between one pin on jack J125 and ground. If voltage does not measure volts, replace ALT 2 field control module. (Refer to 24-30) Alternator 2 faulty. At alternator 2, disconnect jack J125. Measure resistance between one pin on jack J125 and ground. If resistance shows open circuit, alternator coil is damaged. Repair or replace alternator 2. (Refer to 24-30) Annunciation for LOW VOLTS illuminated. Annunciation for ALT 1 does not illuminate when ammeter shows no current. Annunciation for or ALT 2 does not illuminate when ammeter shows no current. No power when BAT 1 switch set to ON position. MCU field control module faulty. ALT 1 circuit breaker open. Loose electrical connections at MCU. ALT 2 circuit breaker open. Loose electrical connections at MCU. BAT 1 switch faulty. At alternator 1 with alternator cables attached, measure voltage between field input and ground. If voltage does not measure volts, replace ALT 1 field control module. (Refer to 24-30)At alternator 2, disconnect J125. Measure voltage between one pin on jack J125 and ground. If voltage does not measure volts, replace ALT 2 field control module. (Refer to 24-30) Reset ALT 1 circuit breaker. Ensure all electrical connections at MCU are secure. Reset ALT 2 circuit breaker. Ensure all electrical connections at MCU are secure. MCU : Disconnect negative cable from battery 1. At MCU, disconnect plug P137. Measure resistance between pin K of J137 to ground. If resistance shows open circuit, test BAT 1 switch and replace if necessary. (Refer to 31-10) 5

6 CHAPTER 24-00: ELECTRICAL POWER CIRRUS AIRPLANE MAINTENANCE MANUAL No external power when BAT 1 switch set to ON position. Ammeter pegs at ±60 amps or indicates abnormal amperage. ALT 1 circuit breaker opens during operation. ALT 2 circuit breaker opens during operation. Airplane power remains on after BAT 1 switch set to OFF position. BAT 2 switch set to ON position energizes non-essential equipment. BAT 1 switch faulty. ALT 1 current sensor faulty. ALT 1 field control module faulty. ALT 2 field control module faulty. BAT 1 switch faulty. MCU battery 1 power relay faulty. P109 and P115 connectors switched. Power diode shorted. Bad isolation diode on PFD or attitude indicator. MCU : Disconnect negative cable from battery 1. At MCU, disconnect plug P137. Measure resistance between pin K of J137 to ground. If resistance shows open circuit, test BAT 1 switch and replace if necessary. (Refer to 31-10) Replace ALT 1 current sensor. (Refer to 24-30) Replace ALT 1 field control module. (Refer to 24-30) Replace ALT 2 field control module. (Refer to 24-30) Test BAT 1 switch and replace if necessary. (Refer to 31-10) MCU battery 1 power relay faulty. Return MCU to approved factory service center for service. Plug connectors correctly. Replace power diode. Replace diode. 6