The Engineering Projects

What is Star Delta Transformation

Hello friends, I hope you all are doing great. In today’s tutorial, we will discuss What is Star Delta Transformation. We will also have a look at its inverse i.e. Delta to Star Transformation. In electrical systems, we have to deal with resistances a lot, arranged in different patterns i.e. parallel, series, mesh etc. Simple single-phase resistive circuits, where resistances are present in parallel or series combination, can be solved by using series or parallel formulas of resistances, there are also few other techniques i.e. Kirchoff's Laws, nodal analysis etc. to solve such circuits. But in the case of complex 3-phase resistive circuits, we can't use these basic formulas & thus need better techniques. Star to delta transformation method is one of them.

The star to delta transformation can also be expressed as Y-? transformation, it is a mathematical method used to solve complex resistive circuits in 3-phase electrical systems. Its name wye-delta is given to it because of its design. As shown in the figure, Star(wye) looks like Y, while Delta looks like ?.  This transformation technique from one form to another was given by Edwin Kennelly in 1899, who was an electrical engineer who belongs to the USA. Besides using in electrical circuitries star-delta transformation can also be used in maths to solve different planer graphs. In today’s post, we will have a look at its working, formula, equation, and uses. So, let’s get started with what is star-delta transformation?

What is Star Delta Transformation?

• The Star-Delta Transformation (Y-?) is a mathematical technique given by Edwin Kennelly in 1899 and is used to solve complex 3-phase resistive electrical circuits by transforming from Star(Y) design to Delta(?) design with the help of formulas.

Before going any further, let's first understand why we need Star to Delta Transformation?

Why Star Delta Transformation?

• We use Star-Delta transformation to simplify complex 3-phase circuits.
• These simplified versions are a lot easier to solve as compared to the original complex ones.
• So, such transformations actually save us from complex calculations, thus reduce errors & save time.

Now let's have a look at Star & Delta arrangements, one by one:

What is Star(Y) Network?

• If all resistances are connected to a common point(also called Joint) from one end, while the other end(of the resistances) is open, this connection styling is termed as Star Network or Y Connection(also called wye circuitry).
• Star Connection is also referred to as open-loop as there's no loop in it.
• Below figure shows the T-Shaped Normal circuit and its equivalent Y-Shaped Connection:

• We haven't performed any transformation in the above figure, instead, we have just draw a single circuit in two different styles, one is called T-shaped, while the second one is Y-shaped.
• In both of these forms, resistances are connected at a single common point called Junction/Joint, represented by J in the above figure.

Now let's have a look at How Delta Network looks like?

What is Delta(?) Network?

• If the resistances are creating a loop i.e. each end of resistance is connected to other resistance, such circuitry is termed as Delta Circuitry, Delta Network or Delta Connection, denoted by ?.
• Delta Connection is also referred to as a closed-loop as it involves a loop.
• Below figure shows the normal loop circuit and its equivalent Delta Circuit:

• Again we are not performing any transformation, instead, we are just displaying a single circuit in its two equivalent shapes.
• In both formats, resistances have created a loop and are connected to one another.

By now, you must have understood the difference between Star & Delta Connection and if you are presented with a circuit, you can easily find whether its a Star or a Delta. Now let's have a look at How to transform from one shape to another(i.e. Star to Delta & Delta to Star).

Star to Delta Transformation

• Transforming a circuit from Star Connection to Delta Connection is called Star to Delta Transformation.
• As shown in the below figure, both connections have the same number of resistances but their values are different.
• So, if we want to convert a Star Connection into a Delta one, then we need to find the values of all Delta resistances i.e. R_A, R_B & R_C.

So, let's have a look at How to drive equations for Star Delta Transformation.

Equation of Star Delta Transformation

• As shown in the above figure, we need to find the values of Delta resistances.
• In order to do so, let's find out the resistance between nodes.

Between N1 & N2:

• In star connection, the resistance between N1 & N2 is equal to R₁ + R₂.
• In Delta connection, resistance R_A is in parallel with R_B & R_C, so the resistance between N1 and N2 will be equal to R_A(R_B + R_C)/(R_A + R_B + R_C).  (using resistance parallel formula)
• As both circuits are equivalent, so the resistance between similar nodes must be equal and will give us equation A, shown below:

Between N2 & N3:

• The resistance between nodes N2 & N3 will give us equation B:

Between N3 & N1:

• The resistance between nodes N3 & N1 will give us equation C:

• Now let's add Equations A, B & C and we will get equation D, as shown in the below figure:

• Now let's subtract equations A, B & C from equation D and we will get values of R₁, R₂ & R₃, as shown in the below figure:

• Now by using these values of R₁, R₂ & R₃, we can get the value of R_A, R_B & R_C, as shown in the below figure:

• So, using these six equations, we can easily convert Star to Delta and Delta to Star, it will get more clear when we solve examples in the next section.

Example of Star Delta Transformation

• The star-? alteration complications are the finest samples to comprehend the idea of the circuitries.
• The resistance in a star system is represented with (X, Y, Z), which can be seen in the above diagram and the values of these resistances are (X= 80?), (Y= 120?), and (Z = 40?).

A= (XY/Z) +Y+X)

X= 80 ?, Y= 120 ?, and Z = 40 ?

• By putting these parameters in the above formula we calculate the value of A.

A = (80 X 120/40) + 120 + 80 )= (240 + 120 + 80 )= (440 ?)

• As we have find value of resistance (B) which is ((ZX/Y) + X+Z).
• Now we put values in this equation to find the value of B.

B = ((40X80/120) + 80 + 40) = (27 + 120) = (147 ?).

• Now we can calculate the value of resistance C by this equation

C= ((YZ/X) +Z+Y)

• Putting value in this equation we get C.

 ((120 x 40/80) + 40 + 120) = (60 + 160) = (220 ?)

Delta To Star Transformation

• Now we see how we can converts delta circuitry back to the star connection.
• Let's solve circuitry which is connected in the delta form and has 3 points a, b, c. The value of resistance among the joints a and b is (R1), resistance among the b and c is (R2), and c and d are (R3).

• The value of resistance among the points and b is given here.

(Rab) = (R1)??(R1+R2)

= [(R1).(R2+R3)]/[(R1+R2+R3)]

• You can see there is another circuitry that is connected in the Y connection it has three branches a, a, c which has resistance (Ra, Rb, Rc).
• If we find the resistance among points a and b then we have.

(Rab) = (Ra+Rb)

• As both of these circuitries are equivalent so the value of resistance is measured among points a and b.

(Ra+Rb)=[(R1). (R2+R3)]/(R1+R2+R3)----(x)

• So the resistance values will also same in the among points b and c.

(Rb + Rc)=[(R2). (R3+R1)]/(R1+R2+R3)---(y)

• And the value of resistance among the c and a will also same.

(Rc + Ra)=[(R3) x (R1+R2)]/(R1+R2+R3)---(z)

• If we add expressions  (x),(y),(z) then we have.

(2)(R1+R2+R3)= 2[(R1.R2)+(R2.R3)+(R3.R1)]

(R1+R2+R3) =[(R1.R2)+(R2.R3)+(R3.R1)]/[(R1+R2+R3)]----(d)

• If we subtract the equation (x),(y), (z) from equation (d) then we have.

Ra =(R3.R1)/(R1+R2+R3)---(e)

Rb =(R1.R2)/(R1+R2+R3)---(f)

Rc=(R2.R3)/(R1+R2+R3)--(g)

• The expression of the Y-? transformation can be defined as.
• From equations e,f,g we can conclude that the resistance in star configuration is equivalent to the multiple of the 2 resistors joined with the identical point divided by the sum of all resistors in the ? circuitry.
• If in the delta circuitry the values of all resistors are identical then the correspondent resistance value (r) in the star circuit will be.

r = (R.R)/(R+R+R)

r= R/3

Advantage of Star Delta Conversion

• These are some advantages of this transformation which are described here.
  • Star transformation is well suitable for transport voltages to long distances and it also has a neutral point that can be used to the unbalanced transient current of the circuitry to the ground.
  • Delta transformation can transport balance three-phase voltage(V) without any neutral (n) wire which marks ? best for Transmission network.

It was a detailed article on Star Delta transformation if you have any questions about it ask in the comments. Take care until the next tutorial.

What is Bypass Diode

Hello friends, I hope you all are doing great. In today’s tutorial, we will discuss What is Bypass Diode. Bypass diode is used in photovoltaic modules. The main purpose of the diode in photovoltaic modules is to reduce the hot-spot (It is a heating phenomena that occurs when the photovoltaic cells are joined in a sequence and due to reverse current lot of power loss occur in the PV module) fact that is harmful to the photovoltaic cells and it can burn the cell if the light coming on the surface of the module is not distributed uniformly. For removal of the hot-spots, bypass diodes are connected with the substring of the photovoltaic devices the single bypass diode is connected twenty photovoltaic cells. Due to such arrangements, photovoltaic modules gives good efficiency during its operating life. In today's post, we will have a look at working, features, applications and circuits of bypass diodes. So let's get started with what is Bypass Diode.

What is Bypass Diode

• Bypass Diodes are connected in photovoltaic arrangements for the protection of such cells that are completely under the solar light and working properly from such cells that are not working or not in the solar light.
• Soler cells are the cheapest way to produce electricity from the sunlight. We can change the location of the solar panels according to our requirements.
• The solar cells are available in numerous power rating, from some mW to thousands mW.
• A solar cell is a photodiode that transformed the sunlight into the electricity. The photovoltaic panel produces electricity when the photocells are connected in a sequence.

• Usually, it is acknowledged that all the cells in the solar panel are producing equal power.
• But there are some conditions that affect the power production of the cell, like environment temperature, humidity in the air location of the panel.
• The principal fact of the power failure of the solar cell is the shading, that reduced the quantity of the light coming to the light. Shading can be due to some tree, wall of the house, or any other building.
• If the shading remains on some cells of the panel there will be less power generation through this panel, to eradicate the effect of the cells that have shading bypass diodes are used in the solar panel.

Features of the Bypass Diode

• These are the main features of the bypass diode.
  • The value of the reverse biasing voltage for this diode is thirty volts.
  • The forward biased functioning current of the diode is fifteen amperes.
  • Minimum forward biased voltage for this diodes is twenty-six milli-volts at eight amperes.
  • The operating temperature for this diode is minus forty to one twenty-five celsius.

Photovoltaic Solar Cell Construction

• In the given diagram, the complete circuit of the solar panel with the bypass diode is constructed, let's discuss it with the detailed.
• The current that we get from the solar panel is the direct current similar to the output power of the battery.
• When the output terminals of the solar cell are open than the voltage at these points will be 0.5 to 0.6 volts.
• The value of the terminals voltage of the solar cells relies on the load attached to the cell.

• For instance, when there is no sunlight due to the clouds the current required by the load will be lighter and the voltage at the ends will be rated value of the cell.
• But if we do increment in load on the terminals of the cells so there is need of the sunlight to maintain the output voltage of the load connected.
• So there is a boundary under that the one solar cell can provide extreme power, it doesn't matter either sunlight is exits or not.
• This amount of the current is recognised as the extreme deliverable current of the cell and denoted as I_MAX.
• The value of the maximum current relies on the area of the cell, angle with the sun, the effectiveness of the cell, and the substances used to assemble the solar cell.
• During the combination of the bypass diode with the photocell,  you should keep in mind the value of the I_MAX.

Diodes in Photovoltaic Arrays

• A diode is a device that used to transforms alternating current in the direct current.
• Unidirectional working feature of the diode can be used in different circuitries to stop the unnecessary movement of the current.
• When the diodes are used in the solar cells that are known as the blocking diodes.
• In solar panel bypass diodes are joined with the one or more than one cells in parallel combination.
• These diodes help to stop unnecessary current movements towards such diodes that are not working properly, or under shading. In this way, we get the desired output current from the solar panel.
• The connection of the bypass diodes is in parallel with the cell to stop current about it while blocking diode is attached series for the reverse movement of the current towards the cell.
• Both bypass and the blocking diode are different categories of the diodes, as they do different work.

Bypass Diodes in Photovoltaic Arrays

• As we discussed that the diode is a uni-direction component. In the given figure there are 2 coloured diodes are connected with the solar panel array.
• Green colour diodes are the bypass diode that is attached with the solar cell in parallel combination for less resistance path.
• The other 2 red diodes are blocking diodes that are linked with every branch of the circuitry in series.
• Both bypass and blocking diodes are similar in physical structure but according to their use, they are different.
• Blocking diodes also recognized as the isolation diode because they provide blocking for the current to flow toward any cell instead of going towards the output load.
• This series diodes help to avoid other parallel cell's current to flow adjacent cell and it also stops the current of the storing batteries to the cell in case of the night when there is zero production of the current at the cell.

Applications of Bypass Diode

• These are the applications of the bypass diode.
  • It used in solar panels.
  • It used in power optimization process and used as a microinverter.

It is the detailed article on the bypass diode I mentioned each and everything related to bypass diode in this post if you have any question ask in comments. Thanks for reading.