In Electrical, Voltage is an Electrical pressure behind the flow of Electrical current. Volt(V) is the unit of Voltage.
1 Volt represents the Electrical pressure needed to get a flow of 1 amp of Electrical current around the resistance of 1 ohm.
Voltage is actually a potential difference between the two nodes. Work done or we can say, A current only flows When there is potential difference in between the two nodes.
The level & type of Voltage depend upon the setup where it’s is going to be applied. It shouldn’t be much higher or much lower.
It should stay in between the permissible range because Machines & Electrical appliances are designed at particular voltage standard. At that standard, Machines work efficiently with optimal maximum life. Much higher or Much lower voltage can damage the system completely.
TYPES OF VOLTAGES
There are two types of voltages AC & DC. AC stands for ‘Alternating Current‘ While DC stands for ‘Direct current’.
Alternating Current (AC)
An alternating current continuously changes its direction periodically at fixed intervals. Due to continuous direction change, Term Frequency exist in Alternating Current.
“An AC sinusoidal waveform shown through a GIF below.”
” Frequency represents how many times an alternating quantity making cycles with respect to time. “
In a GIF above, Alternating current changes direction with respect to time. There are two halves, Positive & Negative. The waveform on above the x-axis is known as positive half. The waveform below the x-axis is known as negative half.
Both positive & negative halves, Together represents a cycle. Hertz(Hz) is the unit of frequency. Normally, At consumer level 50 Hz or 60 Hz is utilized. 50 Hz represents A waveform which is making 50 cycles per second.
” Sinusoidal sign is used as a symbol to represents an alternating current. “
Due to frequency, AC power is further categorized in single phase & multi-phase. (Multi-phase, will be discuss next in this post)
As Discussed, At least two nodes are required for current flow. In AC, A potential carrying node is known as phase. A node acting as a return path for current with the lowest potential, ideally zero, is known as a Neutral.
A name plate of single phase reversible synchronous motor is shown above. Which shows the input rating 230V, 1Φ50Hz. 230 represents the voltage magnitude, 1Φ50Hz represents single phase with frequency standard of 50 Hz.
Direct Current (DC)
Direct current, as per its name, stays direct throughout the time. It does not change its direction. Its magnitude remains constant. That’s why frequency, do not exist in DC, 0 Hz frequency.
“A waveform of Direct current shown through GIF below”
Due to zero frequency, Multi-phase system do not exist in DC. A potential carrying node in DC is known as Positive. While The return path node with the lowest potential, ideally zero volts, is known as Negative. Current flows from positive node to negative node.
An image of 5 Amps 24 V DC power supply shown below. This power supply takes single phase 230 V AC as an input. While It produces 24 V DC as an output.
A double hyphen sign having one hyphen dotted, represents symbol of DC voltage.
RMS of AC & DC
If we compare the waveform of AC & DC. It is easier to find out the magnitude of DC since it is fixed. BUT What’s about AC which is moving with respect to time. How do we calculate the magnitude of AC ?
The answer is RMS (Root Mean Square). RMS value of AC is higher than the average value but lower than maximum value.(shown in an image below)
RMS value of AC produces a same output effect as do produced by the DC of same magnitude. Mathematically, RMS is the square Root of mean value of the instantaneous squared values of a waveform.
In a graph below, RMS value of half waveform is been calculated. Some Instantaneous values been marked on the waveform which is then Squared. Then an average value is calculated from it. At last, square root value is obtained from the average value.
VOLTAGE GENERATION BETWEEN AC & DC
Electric generators are used for voltage generation. Electric Generator is a type of machine which converts mechanical power into an Electrical power.
There are both the type are available which can generate AC as well as DC. Generator mainly contains the two parts stator & rotor. Stator is a stationary part while rotor is a rotating part. Mechanical power is connected with a rotor Which rotates the rotor in required direction with standard speed.
Faraday law of Electromagnetic Induction is the working principle of Generator. The IDEA is when a changing magnetic field links with conductor, An EMF get generated in it.
A GIF below shows the voltage generation in generator. At starting there is no voltage on stator’s winding. But when rotor starts rotating an EMF get generated on stator’s winding.
AC GENERATOR
In Basic generator-AC, stator contains the winding where EMF is going to be generated. While rotor contains the fixed magnet or field winding for magnetic field generation.
When a rotor rotates through a mechanical power, Rotor’s field winding is get excited through an external means. Which results rotor’s field winding becomes electromagnet.
Since rotor is rotating, The phenomenon of changing magnetic is get created. Which starts linking with the armature winding of stator. Which results an EMF get generated in armature winding of stator. EMF is known as Electromotive force which is the main cause behind the voltage generation.
DC GENERATOR
In Basic Generator-DC, Stator contains the field winding or permanent magnet. While rotor contains the armature or main winding where EMF is going to be generated.
Rotor’s winding is configured in a particular pattern LAP or Wave. Winding’s coil ends are connected to commutators strips.
Commutator is the arrangement in which commutator strips are arranged in a circular form. There is a bit equal gap in between the commutator strips. Voltage generated in an armature is an AC voltage. While Commutator is the components which changes the alternating quantity into a direct quantity.
When rotor starts rotating, Magnetic field of permanent magnet of stator links with the rotor the winding. An EMF get generated in rotor winding which is an Alternating quantity.
Commutator arrangement of rotor converts AC quantity into DC quantity. EMF is a reason behind the generation of voltage.
A collage of universal motor shown above. In single left image, A rotor known as armature is been shown. Commutator strips are clearly seen on one end of the rotor Where coil ends are connected. With the help of carbon brushes, Armature is connected with external circuit through commutator strips.
MULTI-PHASES IN AC
Single phase constitute one phase & one neutral. The potential difference in single phase is the difference between phase & neutral. In Alternating quantity due to frequency, multi-phases can be created.
AC voltage is type of vector quantity which contains the both magnitude & angle. More over, In AC, Voltage difference is not arithmetic sum rather it is phasor sum.
In Multi-phase, Voltage is the difference between two phases. Where All the phases have same magnitude. But all are having different phase angle at a same time instant. Which clearly explained through an image representation below.
It all depend upon the winding configuration & Generator design that how much phases & how much voltage is going to be generated .
In a representation of 3 phases below, All the three phases are marked on a same time instant. It is clearly seen that At any particular time instant every individual phase stays at different phase angle .
NAME PLATE OF VFD
For better understanding, We are going to discuss the name plate of VFD next.
A name plate of 2.2 kW 3 phase 400V AC variable frequency drive is shown below. (A variable frequency drive is a type of device which takes ac power supply at fixed frequency as an input. While it produces AC power with variable frequency as an output. Variable frequency AC power is utilized to vary the speed of induction motor. )
In the name plate above, It is clearly seen Input & Output parameters.
INPUT : 50 Hz/ 60 Hz 380- 480 V 3ph 4.3/3.6 A This means input frequency standard is 50 Hz or 60 Hz while voltage range is 380- 480 Volts, 3 phase. Rated current is 4.3 Amps at 380 Volts & 3.6 Amps at 480 Volts.
OUTPUT : 0.1-580Hz 380-480V 3Ph 4.1/3.4A This means output frequency range is 0.1 to 580 Hz while output voltage range is 380 to 480 Volts 3 Phase. Rated current 4.1 A at 380 Volts & 3.4 Amps at 480 Volts.
SUMMARY
- Voltage is an Electrical pressure behind the flow of Electrical current. Volt(V) is the unit of Voltage.
- Voltage is actually a potential difference between the two nodes. Work done or we can say, A current only flows When there is potential difference in between the two nodes.
- Every Electrical machine has rated voltage at which machine operates efficiently.
- Much higher or Much lower voltage can damage the system.
- There are two types of voltages AC & DC. AC stands for ‘Alternating Current‘ While DC stands for ‘Direct current’.
- An alternating current continuously changes its direction periodically at fixed intervals. Due to continuous direction change, Term Frequency exist in Alternating Current.
- Direct current, as per its name, stays direct throughout the time. It does not change its direction. Its magnitude remains constant. That’s why frequency, do not exist in DC, 0 Hz frequency.
- Since AC magnitude continuously moves with respect to time, Changes direction at fixed intervals. To calculate the magnitude of AC, RMS value is used its overall magnitude.
- Mathematically, RMS is the square Root of mean value of the instantaneous squared values of a waveform.
- Electric generators are used for voltage generation. Electric Generator is a type of machine which converts mechanical power into an Electrical power.
- There are both the type are available which can generate AC as well as DC.
- AC voltage is type of vector quantity which contains the both magnitude & angle. More over, In AC, Voltage difference is not arithmetic sum rather it is phasor sum.
- In Multi-phase, Voltage is the difference between two phases. Where All the phases have same magnitude. But all are having different phase angle at a same time instant.