Problem 9-1: Solution
Vrated := 230 volt
Below rated frequency constant volts per hz should be maintained so at 15 hz:
V15 :=
15
60
Vrated
V15 = 57.5 volt
Above rated frequency, the voltage stays constant so V90 = 230 volt
Problem 9-2: Solution
HP60 := 1

Problem 7-1 Solution: You are assigned to select a new 5 hp motor for the plant you work in. The
motor will operate at essentially rated load for two, eight-hour shifts, five days per week. A NEPACT
efficiency motor (efficiency=88.2%) is available at a co

Problem 3-1: Solution homework
kVA kW
The rms magnitudes of the harmonic components of the current are given as follows:
I1 := 118.0 amp
I3 := 60.0 amp
I5 := 20.0 amp
I7 := 19.0 amp
I9 := 12.0 amp
I11 := 12.0 amp
I13 := 9.0 amp
I15 := 9.0 amp
I17 := 6.0 a

Problem 2-9: Solution
S3ph := ( 15 + j 8) KVA
define:
KVA kW
VLL := 208 V
KVAR kW
Vph := 120 V
S3ph
Iline :=
3 VLL
where the overbar indicates the conjugate
Iline = 41.636 22.206i A
Iline = 47.187 A
arg ( Iline) = 28.072 deg
If the load is connected

P2-4. Consider a parallel R-C circuit with R = 20 and -jXC = -j13 , with an applied
voltage of 240 p0o V.
a. Calculate the real, reactive, and apparent power
b. Calculate the total current from the source and the resistor and inductor currents.
R := 20
X

Problem 1-7 :
The average power for the year is the total energy delivered divided by the number of
hours
in a year.
11
Welec := 1.75 ( 10) kW hr
hours := 52 wk 7
day
wk
24
hr
day
3
hours = 8.736 10 hr
Pavg :=
Welec
hours
4
Pavg = 2.003 10 MW
The utilit