Question

The Lights

Q1. Our LED lights are to be powered from a 12 V DC source. Assuming ideal diode characteristics in the rectifier we use and no voltage drops along the wires, what turns ratio N1:N2 is required for a transformer for the lighting subsystem (assume a UK mains system)?

The turns ratio required is ? ( 1:20 / 1:10 /20:1 /10:1)

[1 mark]

Q2. If we have 1000 parking spaces, we have 1000 lights each drawing 20 mA switched on at any one time (we’ll have green for bay is free, red if occupied). What is the total current drawn into the primary side of the transformer?    

[1 mark]

		200 A
		1 A
		2 A
		400 A

Q3. What are the impedances on the primary and second sides of the transformer?

[1 mark]

		Primary 240 Ω, Secondary 240 Ω
		Primary 240 Ω, Secondary 0.6 Ω
		Primary 0.6 Ω, Secondary 240 Ω
		Primary 0.6 Ω, Secondary 0.6 Ω

Answer 1