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Create an abstractive summary of the following aviation document while retaining important acronyms and aviation-specific keywords. Ensure that the summary is concise and accurately represents the main points of the document:
==MAIN AC GENERATION ENGINE GENERATORS==
 The aircraft electrical system is supplied by two engine driven GENerators regulated in speed by integrated drives. GEN 1 is driven by engine 1. GEN 2 is driven by engine 2. Engine generators characteristics are: - 115/200 volts, three phase, - 400 Hz, - 90 kVA. APU GENERATOR A third AC generator driven by the APU can replace one or both main engine generators throughout the flight envelope. APU GEN characteristics are: - 115/200 volts, three phase, - 400 Hz, - 90 kVA. EXTERNAL POWER A ground EXTernal PoWeR connector enables all bus bars to be supplied. External power characteristics are: - 115/200 volts, three phase, - 400 Hz, - 90 kVA minimum. EMERGENCY GENERATOR An AC EMERgency GEN is driven by the Ram Air Turbine (RAT) hydraulic circuit. It automatically provides emergency power in case of failure of all main aircraft generators. Emergency generator characteristics are: - 115/200 volts, three phase, - 400 Hz, - 5,5 kVA. AC TRANSFER The AC transfer circuit enables AC BUS to be supplied by any generator or external power, via the Bus Tie Contactors (BTCs). Generators are never connected in parallel on the same bus. The two normal buses (AC BUS 1 & AC BUS 2) are supplied by the available suppliers in the following priority: - 1: onside generator (
gpt
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1. Is the question multiple-choice question?
No
2. Is it implied multiple-choice question?
No
3. If two experts were independently asked the question, will the final answer be exactly the same?
No

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open