AC theory Flashcards
What is the amplitude?
The peak value of the voltage or current in an AC waveform is called “the amplitude”,
What is the unit of amplitude?
Volts or amperes
What is the typical use of lower case letters in formulas?
Instantaneous values
What is the use of Brackets in formula?
Time dependent values
What are mid-ordinantes?
The positive half cycle is equally divided into n number of portions with equal spaces between them. The equally divided portions are called mid-ordinates and the quotient value of each portion is called the instantaneous value.
How do you calculate average voltage?
To calculate the average voltage, each mid-ordinate value of an alternating waveform is added to its next ordinate’s value; then, the total is divided by the number of mid-ordinates.
What are the features of a square wave?
A square wave indicates the current changing between and in a very short time, compared to the time spent at each extreme.
What are the features of a triangular wave?
A triangular wave indicates a steady rate of change of voltage over each half cycle.
What is the features of a rectangular wave?
If the duty cycle of the waveform is any other value than 50%, (half-ON half-OFF) the resulting waveform would then be called a Rectangular Waveform or if the “ON” time is really small, a Pulse
What are the features of a sawtooth waveform?
The difference between the Triangular and Sawtooth waveforms is that the rise time of the triangular wave is always equal to its fall time, while in a sawtooth wave generator, the rise time may be much higher than its fall time or vice versa.
In three phase systems what are the typically labeling systems?
The phases are usually identified by colours, RED, YELLOW, and BLUE, and the normal phase sequence is R - Y - B. On aircraft, the phases are usually A - B - C.
How many wires are required in three phase systems?
If the phases are kept entirely separate then six wires are required, but if the phases are interconnected then only three or at most four wires are required. On aircraft the 4 or 6-wire systems are the most common, depending on the supply-demand requirements.
How is a star connection configured?
One end of each winding is connected to a common, star or neutral point. The three output lines are taken from the other ends of the windings. A neutral, fourth wire, or earth connection (if required) is also made at the star point.
How many voltages are available in a star connection?
Six
Where will you find phase voltage with a star connection?
Between any line to neutral
