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 showing the exact difference between Star (Y) and Delta (Δ) Connections.
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 and transformers.
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 makes it like a closed loop or mesh circuit. This three-phase, 3-wires system is used in power transmission and transformers.
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.
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. A common wire is taken out from the neutral point which is called Neutral.||In DELTA Connection, the opposite ends of three coils are connected together. In other words, the end of each coil is connected with the starting point of another coil, and three wires are taken out from the coil joints.|
|There is a Neutral or Star Point.||No Neutral Point in Delta Connection.|
|Three phase four wire system is derived from Star Connections (3-Phase, 4 Wires System). We may Also derive 3 Phase 3 Wire System from Star Connection||Three phase three wire system is derived from Delta Connections (3-Phase, 3 Wires System). i.e. 3 Phase, Wire system is not possible in Delta Connection.|
|Line Current is Equal to the Phase Current. i.e.
Line Current = Phase Current
IL = IPH
|Line Current is √3 times of Phase Current. i.e.
IL = √3 IPH
|Line Voltage is √3 times of Phase Voltage. i.e.
VL = √3 VPH
|Line Voltage is Equal to the Phase Voltage. i.e.
Line Voltage = Phase Voltage
VL = VPH
|In Star 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 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)
|The speeds of Star connected motors are slow 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, normal operation without overheating can be achieved.||In Delta Connection, Motor receives 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 Delta connection, The phase voltage is equal to the line voltage, hence it needs more number of turns which increase the total cost.|
|Low insulation required as phase voltage is low as compared to Delta.||High insulation is required as Phase voltage = Line Voltage.|
|Star Connection is a common and general system which is used in Power transmission.||Delta Connection is a typical system used in Distribution system and Industries.|
The same table showing differences between star and delta configurations can be seen below if you face any difficulty while reading the text.
Click image to enlarge
- Delta Connection (Δ): 3 Phase Power, Voltage & Current Values
- Star Connection (Y): Three Phase Power, Voltage & Current Values
- Three Phase Current Values in a 3-Phase System
- Star and Delta Connected Lighting Loads
- 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?