ELT 290 – Homework Assignment #3
Spring 2009
Due: 2/25/2009
Joe is planning to install a wind turbine at his remote vacation cabin in Upper Michigan. The cabin is
located in a remote area where there is no nearby power feed available. The wind turbine will have a 24
volt DC output and power the appliances through an inverter which is located in the cabin. The wind
turbine will be mounted on a 50 foot high tower. The length of the conduit from the base of the wind
turbine tower to the inverter is 50 feet.
Joe has the following electrical appliances in his vacation cabin. The appliances and the power they
draw are given below. All of the appliances operate at 120 volts
(1) television set rated at 100 watts
(2) compact fluorescent lights rated at 75 watts output each
(2) compact fluorescent lights rated at 100 watts output each
(1) laptop computer rated at 60 watts
The inverter itself draws a maximum current of 0.25 amps at 24 volts. Assume an inverter efficiency of
100%. To deliver its rated output power, the input voltage to the inverter must be within 10% of its
rated voltage.
In all cases calculate for a full load condition. Show all calculations!
1. Draw a load diagram of the proposed installation.
2. What the maximum combined load of the appliances in watts?
3. Referring to the previous question, what is maximum current at 120 volts?
4. Based on the previous two problems, what is the maximum power that the wind turbine must
provide?
5. Referring to the previous question, what is the current at 24 volts?
6. Assume Joe is going to use AWG #14 copper wire to supply electricity from the wind turbine to the
inverter. (Refer to the attached table)
a. Calculate the resistance of the wire.
b. Calculate the voltage drop due to the wiring resistance.
c. What is the voltage across the inverter? Is it within the inverter's specification?
d. If it is not, what is the minimum wire size required?
e. What is the minimum wire size required if Joe wants to use aluminum wire?
