021 EL PT3

Question 1

How to increase the range of an ammeter?

Answer 1

Put a shunt resistance in parallel to give less amperage tot the ammeter

Question 2

Draw the schematic of a split bus system

Answer 2

https://www.aviationexam.com/UI/Pages/ImageViewer.aspx?reqFig=27EE9D3A&explanation=0&idFto=0&v=70567

Question 3

What does the GCU do? (6)

Answer 3

• Voltage Regulation
• Overvoltage Protection
• Parallel Generator Operations (control exciter field to match the voltages under load)
• Overexictiation Protection
• Differential Voltage Protection
• Reverse currenct protection

Question 4

What does the CSD do?

Answer 4

Hydromechanical unit that has a motor in “parallel” with the shaft of the drive generator. It can move in the direction of the generator to add (+) extra rpm to the gen and move in the oppisite direction to remove extra rpm. The whole unit, CSD + generator is called the IDG.

Question 5

What does the reactance/inductance/capatitance?

Answer 5

Inductance XL, measured in Henry has the tendency to opposite the electric current due to creating an electric magnetic field around the conductor. It creates a phase imbalance where the I is ahead of the U.
Capitance Xc: measured in farad, stores electrical charge as a little battery, it works with the flow and creates a phase difference where the I lags on the U.
The total reactance is the sum of Xl and Xc.
The impedance: the vectorials um of the reactance and the resistance. Z = X + R. When the Xl and Xc is the same, this is the resonance frequecy. there only is R

Question 6

What are the causes of electricity? (6)

Answer 6

• Friction (static electricity)
• Chemical (battery)
• Magnetic (generator)
• Heat (thermocouples)
• Light (photoelectric)
• Pressure (piezo-electric)

Question 7

What is amperage?

Answer 7

It is the movement of the electrons through a conductor when there is a resistance in the closed circuit where an EMF is applied. Power is created when there is a current I and a voltage U. P = U x I. It is measured in Ampere which means 1 C / s. The results of amperage are heat (joule effect), magnetic field and chemical effects. + verschil AC/DC

Question 8

Why is the current of a startmotor very high in the beginning?

Answer 8

At start the back EMF (E) in the formula U = E - RixI is zero. This Ri is very small so I will be very high at starting. Once the engine is starting turning, the EmF will also grow and so the Ri x I hasn’t be as big as in the beginning.

Question 9

How does a TRU work?

Answer 9

Transfomer Rectifier Unit. It transforms 115V ac to 28V AC, then rectifies it to 28V dc.