AVIATION 325 ELECTRICAL SYSTEM

Electrical System General Description Sources of Electrical Power Power Distribution Normal Conditions Abnormal Conditions

General Description 14 Volt Dual Fed Split Bus Negative Ground DC System

Sources of Electrical Power Battery External Power Unit Alternators

Battery 12 Volt, 35 Amp-Hr Lead Acid Drains & Vents Recharge Battery Bus Battery Master Switch Battery Contactor Starter Contactors Tie Bus (60 Amps)

External Power Receptacle Location Energizes External Power Contactor Starter Contactors Tie Bus Prior to Energizing Battery Master Off All Electrical Equipment Off

Alternators 14 Volts AC, 70 Amp Rectifier (AC to DC) Belt Driven Alternator Field Main Bus 5 Amps Alternator Switch Location

Alternators Alternator Control Unit Voltage Regulator Over Voltage Relay Load Sharing

Alternators An overvoltage relay if output exceeds 17 volts. Voltage regulator maintains effective load sharing. Location

System Monitors ALT Annunciator Light - ALT Switch Turned Off Over Voltage Relay Low Bus Annunciator less than 17.5 volts Ammeter Load Meter Circuit Breakers

Power Distribution Battery Bus Tie Bus Main Bus Non-Essential Bus Avionics Bus

Battery Bus Hot Wired Fuses Equipment Clock Flight Time Hour Meter Maintenance Time Hour Meter Heater Hour Meter

Power Distribution Tie Bus Main Bus Non Essential Bus Essential Electrical Components Tie Bus - Two 60 Amp Circuit Breakers Non Essential Bus

Power Distribution Avionics Bus #1 Avionics Bus #2 Radio Master

Circuit Breaker Panel

Circuit Breaker Panel

Abnormal Conditions Alternator Failure Circuit Breaker Over Voltage Mechanical Failure ALT Light

Abnormal Conditions Single Alternator Failure Alt Annunciator Light Ammeter Reduce Load Dual Alternator Failure Alt Annunciator Lo Bus Battery Load Shedding

Electrical Failure Scenario Okay,you loose your alternators, and you are flying on battery power alone. You’ve just departed on an IFR flight , but the weather is still VFR – you haven’t hit IMC yet. What do you do? Turn back right?

Quiz The over voltage relay will take its respective alternator offline if . . . A. the electrical system’s voltage exceeds 17 volts. B. the alternator’s output voltage exceeds 17 volts.

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