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DC generator parallel operation
UNIT 11 SPLIT SYSTEM
AIM OF THE UNIT:- to understand split system
1 Do your best to answer the brainstorming question. 2 Read the text for general understanding.
3 Make up questions to the text. 4 Find the sentences with the new words in the text. Give the Kazakh or Russian
equivalents of the words.
5 Write sentences with the new vocabulary. 6 Make up exercises as in the UNIT 2page 210(Exercises for better remembering the topic).7 Speak on the topic. Given schemes will help you to remember and understand
8 Find more information about the topic and make up a project work on the topic.
1 What is primary power based on?
2 What is secondary power based on?
This is a completely isolated twin generation system, sometimes called a non-parallelsystem used on twin-engine aircraft. Primary poweris based on two main AC integrated drive generators (typically 40 kVA on each engine). An APU generator (40 kVA) is used as back-up in the event of a main integrated drive generator (IDG) failure. Note that the APU is normally a constant speed device in its own right; therefore an IDG is not required. The advantage of a split-bus system is that the generators do not need to be operating at exactly the same frequency and can be running out of phase with each other. Secondary poweris derived from step-down transformers to provide 26 V AC; transformer rectifier units (TRU) provide 28 V DC for the DC bus bars and battery charging. The right and left generators feed their own bus bars to which specific loads are connected. Each generator bus is connected to a transfer bus via transfer relays. In the event of a generator failure, the remaining generator (engine or APU) supplies essential loads. Control of the system is via a number of flight compartment switches, control breakers and relays arranged to connect and disconnect the generators and busbars. the features of this panel are: Ammeters for the main generators to indicate load Current Ground power available (blue) when external power supply is connected Ground power on/off switch to select ground power onto the aircraft Transfer bus off (amber) when the transfer relay is de-energized (either normal or transfer) Bus off (amber) both respective generator circuit breakers (GCB) and bus tie breakers (BTB) open Generator bus off (blue) if the respective GCB is open APU generator bus off (blue) APU running at 95% RPM, no power from generator.