3.13 Flashcards
What 2 main characteristics differ AC from DC?
Amount of voltage changes with time.
Direction (polarity) changes regularly.
For common AC it could be said that…
Change repeats itself continuously
Average is zero.
Sine curve (easy to generate)
What 2 characteristics is AC represented by?
Peak voltage
Cycle time
What is the peak voltage?
Positive or negative maximum voltage.
What is the cycle time?
Time for a complete periodic cycle.
What is the number of sine waves per second called and what are its units?
Frequency
Hertz
What are RMS values?
Root Mean Square Values.
What are RMS values for?
In AC used for comparison to DC
How is the RMS value found for a sinusoidal supply?
Multiplying peak value by 0.707.
If the RMS value is known how is the peak value found?
Multiplying RMS value by 1.41
What is the formula for frequency?
Frequency (F) = 1 / cycle time (T)
What are generators normally?
Three phase current generators.
What does three phase current generators mean?
3 AC generators are packed in 1 housing .
The 3 coils are displaced at an angle of 120 degrees.
What 2 voltages can occur in a three phase principle?
115V for single phase.
200V from phase to phase.
What is the main advantage of a three phase principle?
Continuous power output which causes less strain to bearings.
