CSD P.O.O.

Question 1

What type of alternator does the CSD use? What is it required to do?
What is the frequency of the power output of the CSD alternator determine by?
What is the alternator driven by? What does this mean?

Answer 1

The AC alternator is required to supply power at a constant frequency of approx. 400Hz on most large aircraft.
The frequency of the power output from an alternator is determined by the speed of rotation of the armature within.
Since the alternator is driven by the engine, it is never spinning at a constant speed.
Therefore, a CSD is required to ensure that the alternator produces a constant 400Hz regardless of the engine speed.

Question 2

What is the principle of operation of the CSD? (6)

Answer 2

• Input shaft rotates 2 identical gears to drive a differential unit and Fixed displacement hydraulic pump
• Fixed displacement pump will pressurise oil under high RPM and apply a brake to a variable displacement pump through the control cylinder
• Also maintains pressure to governor which maintains stable pressure to control cylinder
• Variable displacement pump drives a gear linked to differential unit and to output shaft
• Differential unit similar to car clutch and is constantly slipping under every situation except 400RPM engine operation
• Output shaft also drives oil pump for charge oil