Transcript Alternating Current

Alternating Current
Chapter 12
Generating AC (12-1)
Generating AC (12-1)
Armatur
e
Sine
Wave
Positive
Alternation
Negative
Alternation
One Cycle
AC Cycle - Alternation
• Cycle – The complete revolution
of an AC generator.
• Alternation – One cycle of a AC
generator is made up of two
alternations.
• Positive Alternation
• Negative Alternation
AC - Frequency
• Frequency – The number of
cycles in a second.
• Hertz – The unit for frequency.
Household Current – 60Hz
60Hz – 60 Cycles/second
Degree of Rotation
Degree of Rotation
Degree of Rotation
Degree of Rotation
Peak
Peak to Peak
Amplitude
Time
Period t
Peak
AC Values
Amplitude – The value of the wave from
zero. (- +)
Peak – The maximum value of the
amplitude. (- +)
Peak to Peak – The value measured
from one Peak (+) to the other Peak (-).
Period – The time of one complete sine
wave. (seconds – s)
Frequency – Number of cycles per
second. (hertz – Hz)
f=
1
t
AC
Values
50m
Peak =500mV
Period =s
Peak to Peak
1000mV
=
1
20
f=
Frequency =
0.05s
Hz
Effective / RMS Values
• Effective value of AC is the amount
of AC that produces the same
heating effect as an equal
amount of DC.
• The Effective value is determined by
the mathematical process call the
Root Mean Square method or RMS.
Vrms = 0.707 VPeak
AC
Values
Effective Voltage =
Vrms = 0.707 VPeak
Vrms = 0.707 (500mV)
Vrms = 354 V
Non-Sinusoidal Wave
Forms
Square Wave
Square Wave – Pulse
Width
Pulse Width = ½ Period
Non-Sinusoidal Wave
Forms
Non-Sinusoidal Wave
Forms
Non-Sinusoidal Wave
Forms
Fundamental Frequency
• The lowest frequency produced by
any particular instrument is known
as the fundamental frequency.
Harmonics
• Harmonics are higher frequency sine
waves that are exact multiples of the
fundamental frequency.
Volts
Time(ms)