Three-phase circuits are used in transformers, generators, distributors to generate electric power. It has three voltages which are interconnected using either star or wye connection or delta or mesh connection to save copper and make the system less expensive. T
Star Connection vs Delta Connection
Star connection is used in the long-distance transmission lines, and delta connection is used in short distance distributed network. The star connection uses 4 wires, three for connection to the external circuit and one for the neutral point. The delta connection uses three wires to form a mesh loop.
In the Star connection system, the starting or finishing ends are connected to the neutral point. It uses four wires to connect to the external load circuit, out of which three wires for the external circuit and the fourth fire are for neutral connection forming a three-phase star connection.
Delta Connection is a system the starting end is connected to the finishing end of the phase forming a mesh loop. A delta-connected system does not have a neutral point.
Comparison Table
| Parameters of Comparison | Star Connection | Delta Connection |
|---|---|---|
| Definition | It is a three-phase four-wire start connected system generally used in long-distance transmission of power in the distributed network. | It is a three-phase three-wire delta connected system generally used in the short-distance transmission of power in the distributed network. |
| Neutral point | It has a neutral point where all the starting or ending points of each resistor meet. | There is no neutral point in the delta; instead, the starting point of one resistor is connected to the ending point of the other resistor forming a mesh loop. |
| Line Voltage | Line voltage = √3 *Phase voltage | Line voltage is equal to phase voltage. |
| Line Current | Line Current is equal to Phase current. | Line current=√3 * phase current |
| True Power | √3*Line Voltage *Line Current*CosΘ Where Θ is the difference between phase voltage and phase current | √3*Line Voltage *Line Current*CosΘ Where Θ is the difference between phase voltage and phase current |
What is Star Connection?
Star connection is one of the forms to interconnect the three-phase circuit. It has a neutral point N where all the similar ends of the resistors either start or finish joins.
In this system, the line current and line currents are equal. The potential energy at a neutral point is zero.
Formulae
EL (line Voltage) =√3*Eph (phase Voltage) or Eph = EL
Actual power (p) = √3*EL*IL* CosΘ here Θ is the angle obtained between phase voltage and phase current.
Apparent power=√3*EL*IL
What is Delta Connection?
The delta connection is the other form to interconnect a three-phase circuit. In this circuit, the phases have dissimilar ends where the start point of a resistor is connected to the endpoint of the other resistor to form a mesh loop.
In the balanced delta-connected system, the line voltage and phase voltages are equal. This system does not have a neutral point. Therefore, only three wires are used in the system.
Formulae
IL (line current) =√3*Iph (phase current) or Iph = IL
Actual power (p) = √3*EL*IL* CosΘ here Θ is the angle obtained between phase current and phase voltage.
Apparent power=√3*EL*IL
Main Differences Between Star Connection and Delta Connection
- Star connection system is a three-phase four-wire system with a neutral point, whereas Delta connection system is a three-phase three-wire system without a neutral point.
- Star connection systems are used for both low and heavy loads of power transmission in long-distance, whereas Delta connection systems are used for heavy load transmission in a shorter distance.
References
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