•Introduction: In the study of Alternating Current it is important to Identify the forms of AC signal generation.
•The two basic sources of AC power are electromagnetic sine waves created by:
•1-Electromagnetic AC generators
•2- Electronic equipment such as frequency generators and oscillators.
•Three important elements studied under AC power signals:
•A- Frequency.
•B- Amplitude.
•C-Period
Frequency definition: How many times in a given period the frequency oscillates. F (Hertz) = 1/t(Seconds)
Consider the following F calculations:
a)What is the frequency of a signal that oscillates every
100 milliseconds?
F= 1/t , F = 1/0.100 seconds = 10 Hertz (10 Hz)
b) What happens if the time of oscillation is reduce to 50
Milliseconds?
F=1/t, F = 1/0.010 seconds = 100 Hz…the frequency increases or doubles
c) What happens if the time is double from the original?
F= 1/t, F=1/0.200 seconds = 5 Hz…the frequency reduces.
Frequency and Time are inversely proportional.
Period definition: The time required for the completion of one cycle. Also the reciprocal of the frequency:
T (seconds) = 1/f(Hertz)
Consider the following Period calculations:
a)What is the Time or period of a signal that
with a frequency of 60 Hz per second?
T = 1/f = 1/60 Hz = 0.017 seconds or 17.7 milliseconds
b) What happens if the frequency of oscillation is reduced to 30 Hz?
T = 1/f = 1/30 Hz = 0.033 seconds or 33.3 milliseconds…the time increases or doubles.
c) What happens if the frequency is doubled from the original?
T = 1/120 Hz = 0.008 seconds or 8 milliseconds….time reduces.
Time and Frequency are inversely proportional.
Amplitude definition: How much voltage the signal carries and it is given in RMS (Root Mean Square), either in Peak-to-Peak or just Positive Peak or Negative Peak.
Vrms = Vpx0.707
Vp = 1.414Vrms
Vpp = 2.828Vrms
Consider the following Amplitude calculations:
a)If the Vp = 2 volts, what is the Vrms value?
Vrms = Vpx0.707 = 1.414rms
b) If the Vrms = 1.414, what is the Vp value?
Vp = 1.414 x 1.414 = 2.828Vp
c) What is the Vpp value if Vrms is 1 volt?
Vpp = 2.828x1Vrms = 2.828
Vrms is the voltage value required by a AC source to do the same work of an DC source can do.
-One revolution of the loop generates one cycle of the wave voltage. True
-A four-pole generator has 2 south poles and 2 north poles. True
-An electronic circuit that produces repetitive waves is called: *-Oscillator
-AC generators are called: *-Alternators
-Frequency in a generator is directly proportional to: *-Rate of rotation
F = pole pair times number of revolutions per minutes.
AC Power Sources