Homework 6 - EE491 Issued : October 7, 2002 Due: October 11, 2002 Reading assigment : Wildi 2.162.27, 4.04.13 Homework 6 - EE491
Issued : October 7, 2002
Due: October 11, 2002
Reading assigment : Wildi 2.162.27, 4.04.13
1. A conducting circular loop of a radius 0.1m is situated in the neighborhood of a very
long power line carrying a 60Hz current, as shown below with d=0.15 m. An a-c
milliammeter is inserted in the loop and reads 0.3mA. Assume the total impedance of
the loop including the ammeter is to be 0.01 Ohms.
(a) Find the magnitude of the current in the power line.
(b) To what angle about the horizontal axis should the circular loop be rotated in
order to reduce the ammeter reading to 0.2mA?
d
b
2. Wildi 25
3. Wildi 44
4. Wildi 49
5. Wildi 410
6. Please submit a solution for this problem to count as Quiz 6
Youre working for a company which needs an 8kVA, 4kV:400V transformer for a
system which has a 50Hz frequency. A 10kVA 4000:400V transformer is available but
it was designed to operate at 60Hz. The transformer in question has an eciency
of 90% when supplying rated load with power factor=1. Assume that winding losses
make up 2 percent of total losses. Use what you know about magnetics and Faradays
law to answer the following questions. Can this transformer be used in the 50Hz system to power an 8kVA load (PF=1) if
4kV is applied to the primary?
Specically will any of the voltage or current ratings on the transformer be exceeded?
Will the transformer get hotter than at 60Hz?
What assumptions did you make to reach your conclusions?
Do you need more information to make your nal decision? If so what is it?