Difference between Star and Delta Connections – Comparison Of Y/Δ
Comparison between Star and Delta Connections
We mostly use the terms star and delta in electrical systems while discussing three phase AC circuits and electric motors. Below is a given table which compares both Star and delta connections which shows the exact difference between Star (Y) and Delta (Δ) Connections.
Star Connection:
Star connection “Y” is obtained by joining together similar ends of coils either “starting” or finishing. The other ends are joined to the line wires. The common point is called the Neutral or Star Point. This three-phase, 4-wires system is used in power distribution, transformers and small scale domestic and residential applications.
Delta Connection
Delta or Mesh Connection “Δ” is obtained by connecting the starting end of the first coil to the finishing end of the second coil and so on (for all three coils) which forms like a closed loop or mesh circuit. This three-phase, 3-wires system is used in power transmission, transformers, and large scale industrial and commercial applications.
In both systems, the Voltage between two phases (Line to Line) is known as Line Voltage, while the voltage between Phase to Neutral (Line to Neutral) is known as Phase voltage. The voltage between any line (or phase) and Neutral is single phase while voltage between all three lines (or phases) is known as three phase voltage. Keep in mind that the power in both systems are always equal and same as it is the game of different levels of voltages and currents only used in different systems based on the requirement.
The following table better summarizes the differences and comparison between Star and Delta Connection.
| STAR Connection (Y) | DELTA Connection (Δ) |
| In STAR Connection, the starting or finishing ends (similar ends) of three coils are connected together to form the neutral point in the shape of letter “Y”. A common wire is taken out from the neutral point which is known as the Neutral Wire. | In DELTA Connection, the opposite ends of three coils are connected together which forms the shape of Greek alphabet “Δ”. In other words, the end of each coil is connected with the starting point of another coil, and the common joints form the three phase wires. |
| There is a Neutral or Star Point. | No Neutral Point in Delta Connection. |
| There are Four conductors in the star connection (3 Phase Wires + 1 Neutral Wire). | There are Three conductors in the delta connection (3 Phase Wires e.g. All are phases). |
| Three phase four wire system is derived from Star Connections (3-Phase, 4 Wires System). 3 Phase 3 Wire System is also possible in the Star Connection as Neutral is optional if not needed. | Three phase three wire system is derived from Delta Connections (3-Phase, 3 Wires System). i.e. 3 Phase, 4 Wires system is not possible in Delta Connection due to the absence of the Neutral wire. |
Line Current is Equal to the Phase Current. i.e.
|
Line Current is √3 times of Phase Current. i.e.
|
Line Voltage is √3 times of Phase Voltage. i.e.
|
Line Voltage is Equal to the Phase Voltage. i.e.
|
In Star Connection, the total Power supplied by three Phases could be found by:
|
In Delta Connection, the total Power of three phases could be found by:
|
| The speeds of Star connected motors are slower as they receive 1/√3 voltage. | The speeds of Delta connected motors are high because each phase gets the total of line voltage. |
| In Star Connection, Smooth starting and operation with nominal power and normal operation without overheating can be achieved. | In Delta Connection, motor receives the highest power output. |
| In Star Connection, the phase voltage is low as 1/√3 of the line voltage. Therefore, it needs a low number of turns, hence saving in copper. | In a Delta connection, The phase voltage is equal to the line voltage, hence it needs more turns which increase the total cost. |
| Low insulation required as phase voltage is low as compared to Delta. | More insulation is required as Phase voltage = Line Voltage. |
| Star connection is preferred for long distance transmission and distribution as it requires low insulation and has a Neutral which helps to balance the circuit. | Delta connection is preferred for shorter distance transmission and distribution as it requires more insulation and has the problems of unbalanced currents. |
| Two different voltage levels can be achieved by using star connection i.e. single phase and three phase supply. (3 Phases and Phase + N). | Only a single magnitude of voltage can be achieved by using the delta connection e.g. three phase supply across three phase conductors. |
| Star connection is preferably used in the domestic and residential applications for single phase supply (Line or Phase + Neutral = 230V AC – IEC) and three phase supply (Three Phases = 400V AC – IEC). But the case is different and complex in US – NEC). | Delta connection is generally used in the industrial and commercial applications for three phase supply (Three Phases = 400V AC – IEC). This role is not applicable in the US – NEC as they offer different levels of voltages based on the system requirement). |
| Star connection is commonly used for appliances which need less amount of starting current e.g. small load applications. | Delta connection is generally used for high starting torque applications e.g. large electric motors in the industries etc. |
| Star Connection is a common and general system which is used for both single phase and three phase power transmission & distribution. | Delta Connection is a typical system commonly used in the distribution Networks & systems and Industries. |
For reference, the following table can be downloaded in the image format for later use which shows differences between star and delta configurations.
Click image to enlarge
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- STAR-DELTA Starter Motor Starting Method Without Timer
- Open Delta Connections of Transformers
- How to Wire 240V, 208V & 120V, 1 & 3-Phase, High Leg Delta Main Panel?
Comparison bw star and delta made me understand why star delta starter is used for 3 phase ac motors.
star is used for below 5 hp motors and delta is used for above 5 hp ….. when motor gets starts ,it starts with star after that it changes to delta by using timer because, when the motor stars motor gets highs amps at first star works after that delta works
Its bcoz to increase the speed of motor while starting gradually.. since the phase voltage is 1/√3 of line voltage the starting speed of the motor will get reduced after a specific time it have to get changed to delta inorder to deliver more power
Please correct – Delta Connections – 3rd point –
It should be
“Three phase three wire system is derived from Delta Connections”
not Star Connections.
In the image also.
Thank you.
Thanks for Correction. :)
Why Star connection and Delta connection is necessary for Motors ?
Motor starting torque is high current control in star connection that necessary star cannection
star connection is required at the starting o motor because a motors takes 5-10 times more current at starting and if delta current is given it may start immediately but this may reduce the life of motor
Mr Khan, Pls we are talking about star ? and delta in general here not the process of star – delta connection to start a heavy motor.
Thank u
mr. Khan, thanks for the explanation.. it was the best way to describe it.. dont care about Ibrahim Fatawu
Thanks for appreciation….
Mr. Khan u r right
THANKS FOR GUIDE
i need the delta and star
Very good website
can any one tell me in star delta mode,, in which state motor take high or more current…. in Star or Delta
Star has high starting currents and high starting torque
Thanks for the guidance…
Thanks SAR very good sejestion
I WANT TO BE THE PART OF THIS GOOD KNOWLEDGE SHARING WEB SITE.
You are most welcome dear….
how do I generate neutral from delta connection
Please provide more information… For which purpose, do you want to do that? You mean, You want a single phase supply with neutral wire from three phase (Delta) Generator or what?
Thanku for guidance star and delta cannection explain
What is diffrence between neutral and earthing. Please give me ans
We have already published the post… You may read it here
neutlal return current to the source while earthing neutralize the circuit
neutral is a constant but earth varies from low to high
Thanks for the guidance.
Hello all;
i need the Circuit diagram of how to turn on automatically a 3 phase Generator?
Thanks for the guidance.
HOW WILL YOU TEST THE RESISTANCE OF A STAR CONNECTED MOTOR
Whether u connected in star or delta….speed doesn’t varies know…only torque differs….change the answers in difference column
Good day!
In our industrial electrical facilities has some motor like big cooling fan has delta connection (50HP) If we will change the motor winding connection from delta to star, is any benefit from energy Saving point of view.
your feedback is highly appreciated.
Hi shivaraj,
if you change the motor getting high current and temp, my point of view can’t change like Delta to star.
Take long time to start motor. star can give High starting torque. Delta can’t ,
if less than 60% load can possible to change.
Thanks
Sir ye star me neutral kyu hota h,delta kyu nhi hota h?
greetings
i think the star connection is used for the distribution (to provide the single phase voltage ) , and the delta is used for transmission (higher voltage , more insulation is required but we transmit by OHTL (air is our insulator ) .
its reversed in the article i think ..or may be there is something i am missing .
Dear admin
Please check the last point, is this true that delta used for distribution and star used for transmission ?
Which type of connection os better for 25hp Motor if it is connected to power pack….. we connected in star is it ok
u have to operate motor in star – delta connection both, initialy 25 hp motor required more force to move its shaft but as soon as it attain some speed it an be transferred to delta. we use this type of combination above 5 h.p. motors.
I want to use motor for running compressor motor details 440v,60hz, and 130Amps normal working current ,power 80kw load.
Starter is DOL.
Please give advise how should I connect motor terminal in star or delta
Thanks
Dear sir,
can u prove why star connected motor takes low current than delta connected motor.
Hi! Does the imbalance between the phases can be caused by type of connection? Ex. There’s phase? 2 pole induction motor and phases have the following values of current: A=130A, B = 125A, C=120A. Why they’re not the same?
Between star and delta connection which of them takes a high voltage either in primary or secondary coil
Why delta connection is require for motor??????
In home….what kind of connection we use????
They are single Phase motors.. And obliviously, We use Single Phase supply…
best comparison between delta and star connection
There is no change in speed for both star and delta connection for induction motor Speed N = 120F/P i.e. Speed depends upon only supply frequency and No of pole in motor speed can not change due to voltage variation for Ac induction motor – star delta connection used for Ac induction motor.
if u change voltage than speed of motor will be vary i think…
please sir according to your circuit diagram on connection of motor in star delta why is the star terminal in series and the delta in parallel
One 63.5 KVA genset 3-Phase is connected to load( machine). Starting in Star connection is OK but during the load transfer to delta connection , motor (machine) trips off. What can be the possible reasons?
If in place of star connection,we give delta connection.What will happen to the Motor?
if iam using vfd( Voltage Frequency Drive) for motor, Witch connection require ?
I believe that the Power formulas are incorrect “Phases could be found by: P = √3 x VL x IL x CosФ …. Or P = 3 x VPH x IPH x CosФ P = √3 V x 1 In Delta Connection, the Total Power of three phases could be found by: P = √3 x VL x IL x CosФ … Or P = 3 x VPH x IPH x CosФ P = 3 x V (1/√3) shouldn’t they both be P = √3 x VL x IL x CosФ, in balanced load. but for sure they both should have a current component. Thanks very good site for what I have used it for.
Hi
Qus1
What happen when motor on without rotor? I know heat will be produced and coil should be burn . But I want exacted reason it will be help
Qus2
1 what happen when motor run in star connection continually or Delta? Is it possible,
I have 20hp 3phase motor that connected in delta but I want to change in star. If connect in star ampere increase or decrease. Pls comment.
Which hp motor you have.
I want to get something here,if star can be referred as power transmission and delta as power distribution dat means how can we figure out and equipment or an inductive load I mean motor that can handle both of them
I want to rewind a motor of star connection of 24 slot but i need a rewinding designed or connection designed.Thank