alternating current chapter 12. generating ac (12-1)
TRANSCRIPT
Alternating Current
Chapter 12
PositiveAlternation
NegativeAlternation
One Cycle
SineWave
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
Amplitude
Peak
Peak
Time
Peak to Peak
Period t
AC ValuesAmplitude – 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 = t1
AC Values
Peak =Peak to Peak =
Period =
Frequency =
500mV
1000mV
50ms
f = 0.05s120
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)