EEEE2045: Power Electronics

Question 1

Why is switching used in Power Electronics Circuits?

Answer 1

• To give pulsed
  energy flow which when paired with energy storage elements, gives ‘smooth’ control of power flow
• To give very efficient power conversion

Question 2

What are the assumptions made when analysing an ideal power electronic circuit?

Answer 2

• Semiconductor devices are considered as ‘Ideal’ switches
• Inductors are treated as ‘Ideal’
• Capacitors are treated as ‘Ideal’

Question 3

What does the assumption: (Semiconductor devices are considered as ‘Ideal’ switches) entail?

Answer 3

• No voltage across them when they are conducting (ON)
• No current flows when they are blocking (OFF)
• Instantaneous switching between the ON and OFF states

Question 4

What does the assumption: (Inductors are treated as ‘Ideal’) entail?

Answer 4

• Zero resistance in the winding(s)
• No power loss in the magnetic material (Zero eddy current loss and
  hysteresis loss)

Question 5

What does the assumption: (Capacitors are treated as ‘Ideal’) entail?

Answer 5

• Zero series resistance in the capacitor
• Zero power loss in the dielectric

Question 6

What do the assumptions made when analysing an ideal power electronic circuit allow for?

Answer 6

The circuit to have 100% efficiency

Question 7

What are the ‘Four Rules’?

Answer 7

• ΔI = voltage time area/inductance (VTA/L)
• ΔV = current time area/capacitance (ITA/C)
• Average voltage across all inductors (taken over a period) = 0
• Average current through all capacitors (taken over a period) = 0