Embedded Files
What is Alternating Current?
What is Alternating Current?
Alternating current is an electricity supply which is delivered to every consumers premise or factories buildings to provide electric power to all their connected loads. Electricity supply is distributed to all places through overhead lines known as transmission lines.
Alternating current (AC) is the flow of electric charge that periodically reverses direction. If the source varies periodically, particularly sinusoidally, the circuit is known as an alternating current circuit.
Figure on the left is the alternating current symbols.
AC properties
AC properties
Alternating Current (AC) is a type of electric current, in which the direction of the flow of electrons switches back and forth at regular intervals or cycles.
The elements of AC are:
frequency
period of time
amplitude
a. Supply Frequency
a. Supply Frequency
Frequency of wave form is usually obtained by inverse time period.
- units in hertz or Hz.
- 1 cycle of alternating current representing 1 period of time.
AC Wave form
AC Wave form
Figure above is known as sine wave.
b. period
b. period
It mean time taken to complete one cycle of the wave.
Formula: time (second), t = 1 ÷ Frequency
c. amplitude
c. amplitude
Defined as the high peak of a sine wave.
Root Mean Square ( RMS )
Root Mean Square ( RMS )
In mathematics and its applications, the root mean square is defined as:
the square root of the mean square.
the average of the squares of a variable quantity.
In terms of voltage, the root mean square voltage is called the effective voltage, as opposed to the peak voltage which corresponds to the maximum AMPLITUDE of the voltage variations.
1) RMS value = 0.707 Peak value
RMS value (root mean square) or effective value of sine wave shaped voltage is equal to 0707 at the peak value of the product
2) The average value = 0.637 Peak value
The average value of a sine wave for the positive half cycle is the peak to peak divided by the π (pi or 3.144)
Figure above showing position of Vrms and Vavg in sine wave.
Example calculations for Voltage rms and Voltage average
Example calculations for Voltage rms and Voltage average
Given the voltage peak is 230 volts AC, calculate the Vrms value?
Solution: Vrms = Vp x 0.707 = 230v x 0.707 = 162.61 volt
Given the voltage peak is 240 volts AC, calculate the Vavg value?
Solution: Vavg = Vp x 0.707 = 240v x 0.637 = 152.88 volt
Basic AC generation
Basic AC generation
An alternating current is produced by an electric generator. All power generating stations have a basic component.
fix coil or winding known as stator coil
moving coil or armature, it is also known as rotor coil
Turbine-based AC electrical generation is when an electric current is induced by the interaction between charged particles and magnetic fields which converts the kinetic energy of the turbine into the kinetic energy of electrons.
Figure above showing the wave generated when the shaft is rotating in one direction only.
Danger of AC
Danger of AC
When you accidentally touching an exposed conductor of LIVE energized loads, this cause:
current flow through your body from point of contact going down to ground. This is known as electrocuted, if you are wearing rubber shoe/slipper then current will not flow through the ground. You receives a small shock like an ant bite.
cause heart failure, due to high current flowing through your body, you heart may received shock. This may cause your heart to beat abnormally then causing other body function to behave out of ordinary.
burning at point of contact, you may suffer pain and some time may cause severe burns on your skin near the point of contact.
AC protection devices will take actions by residual current device (RCD) which quickly act to cut off the electricity supply upon detects abnormal current flowing in the supply lines.
Page updated
Google Sites
Report abuse