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With a delta connection, picture a triangle. Each side of the triangle is a transformer or motor winding. Call the 3 corners of the triangle A, B, and C. There are only 3 wires except for a safety ground, which has no connection to, nor is any part of, the power transmission service lines.

All 3 windings have the same voltage, say for example 208V. If you take a meter, you will measure 208V between A and B, between B and C, and between C and A.

With a wye connection (also called a star connection) take our triangle above and use your wire cutters (literally) to cut the triangle apart at the corners. rearrange the three sides (transformer or motor windings) to form a Y. Where the three sides join in the center, connect a fourth wire. Call this wire "neutral". Call the three ends A, B, and C. Connect the 3 supply service lines to A, B, and C.

Now if you measure with your meter you will see 120V between the neutral and any single phase (A, B, or C), but you will still measure 208V between A and B, B and C, and C and A. The 208V is used to power three-phase loads and the 120V is very handy if you need to power a 120V single-phase load, such as a toaster! In a wye system, the supply service line-to-line voltage is 1.73 times the voltage from any phase to neutral.

Delta power is used for motors, 3-phase heaters, anywhere you don't need a neutral.

The biggest use of delta is in power transmission. Way too expensive to run a fourth wire all those miles, especially since a 3-wire delta transmits the same amount of power. Look up at a transmission tower and you see three phases and a ground wire for lightning suppression. No neutral.

At the destination, (a distribution transformer outside the home or business), the primary of the transformer is wired delta and the secondary is wired wye. This creates the neutral that can be used to derive single-phase power where needed. The neutral is grounded at the service entrance. Wye systems must be used where you have single phase loads that you must feed.

Interestingly, if you hide the neutral, you really can't tell the difference between star and delta systems. The phase-to-phase voltage is exactly the same. Most of the time 3-phase motors (which are internally delta-connected and have no neutral) are fed from a wye-connected source, simply omitting the neutral.

Another answer

The three phase windings in a generator /tranformer/motor can be interconnected in two ways. If the similar ends of the coils are connected together and the other ends are connected to the 3 incoming supply service lines, that is called "star connection". The internally-connected point is brought out as the neutral connection. The service line "line-to-line" voltage (between any 2 lines) is 1.732 times the voltage between any line and neutral. Thus we can get two voltages for distribution within a building or site to supply lighting and power. However the service line currents are the same as the phase winding currents.

If the dissimilar ends of each winding are labelled A and B and the three windings are then connected together B->A, B->A, B->A, and the 3 incomiing supply service lines are then connected to the junctions, it is called DELTA. Here the values of line voltage and phase voltage are the same while the service line currents are 1.732 times the phase winding currents.

Technical information

When the windings of a 3-phase motor are connected in STAR:

  • the voltage applied to each winding is reduced to only (1 /.'/'3) [1 divided by root three] of the voltage applied to the winding when it is connected directly across two incoming power service lines in DELTA.
  • the current per winding is reduced to only (1 /.'/'3) [1 divided by root three] of the normal running current taken when it is connected in DELTA.
  • so, because of the Power Law V [in volts] x I [in amps] = P [in watts],

    the total output power when the motor is connected in STAR is:

    PS = [VL x (1/.'/'3)] x [ID x (1/.'/'3)] = PD x (1/3) [one third of the power in DELTA]

    where:

    VL is the line-to-line voltage of the incoming 3-phase power service

    ID is the line current drawn in DELTA

    PS is the total power the motor can produce when running in STAR

    PD is the total power it can produce when running in DELTA.

  • a further disadvantage when the motor is connected in STAR is that its total output torque is only 1/3 of the total torque it can produce when running in DELTA.

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13y ago
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12y ago

The voltage difference between star and delta is 1.732, the square root of 3, or, going from delta to star, 1 over 1.732, which is 0.5774. That is the same as the current difference, neglecting motor efficiency at the two different operating voltages.

The power difference between star and delta is 1.7322, or3, and between delta and star is 0.57742, or 0.3333.

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In a wye connection, the line current is equal to the phase current.

In a wye connection, the line voltage is equal to Sq. root of 3 (1.73) x phase voltage

In Y connected loads and sources, the line voltages will always be greater than phase voltages, and line currents equal to phase currents.

When a Y connected load or source is balanced, the line voltage will be equal to the phase voltage times the square root of 3.

In a delta connection, the line voltage is equal to the phase voltage.

Because each line conductor attaches at a point between two windings, the line current will be the vector sum of the two joining phase currents.

In a delta connection, the line current is equal to Sq. root of 3 (1.73) x phase current.

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11y ago

star connection like y whle delta connection like a triangle. in star connection there is adifference between line voltage and phase voltagewhi delta connection line voltage and phase voltage are same. in star connectin line voltage is always greater than phase voltage

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Q: What is the difference between an electrical 3 phase delta connection and a star connection?
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What is the difference between an open delta and an open wye connection?

An open delta connection is a delta connection with one phase removed, but still supplied with three line conductors. An open wye is a wye connection with one phase removed, supplying a three line conductors and a neutral conductor. An open-delta/open-wye is a method of providing a reduced-load three-phase supply using just two single-phase transformers, rather than the preferred method of using three single-phase transformers.


What is the reason motor runs delta connection?

Motor run delta connection because in delta connection it is less ampere needed and it sometimes it change the wye connection because of the available suply


Why does delta's connection draw high current?

For the same amount of power, a star or delta connection will use the same line current. However a delta connection supplies sqrt(3) times less current to the device on each of its connections because the voltage is sqrt(3) times more. The apparent contradiction comes about because in a delta connection each connection to the line is shared between two connections to the device (Historikeren 20-07-2015).


Differentiate delta to delta connection of the transformer to delta to Y connection?

In delta to delta there will be no ground on both primary and secondary sides. Leave the primary side but we take care on secondary side. If there any fault occurs on the secondary then there will be unbalanced voltages between the phases results in the flow of current through the secondary windings so only we are using star on the secondary side while having neutral to prevent such a current flow.


Why most generation firm uses delta connection in the secondary side?

Many industrial installation use delta a secondary connection because it reduces the cost associated with a fourth wire.

Related questions

What is the difference between a Y - delta starter and a star - delta starter?

No difference. Y is used as a symbol to indicate the star connection.


What is the voltage phase shift between primary and secondary line voltages in star-delta transformer connection?

The voltage phase shift between primary and secondary connections in a transformer is 180 electrical degrees.


Why does an electromagnetic brake designed for a star connection not work in delta?

Probably the reason is in the different voltages between the star and delta connection voltages. An electromagnetic brake designed for the lower voltage of the star connection would burn out or open when introduced to the higher voltage of the delta connection.


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How do you convert star delta connection to delta star connection?

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What is the difference between an open delta and an open wye connection?

An open delta connection is a delta connection with one phase removed, but still supplied with three line conductors. An open wye is a wye connection with one phase removed, supplying a three line conductors and a neutral conductor. An open-delta/open-wye is a method of providing a reduced-load three-phase supply using just two single-phase transformers, rather than the preferred method of using three single-phase transformers.


How much you can save the power from converting star delta connection to star connection?

The power of a three-phase load is the sum of the three individual loads. It makes no difference whether they are connected in star (wye) or in delta.


What is the reason motor runs delta connection?

Motor run delta connection because in delta connection it is less ampere needed and it sometimes it change the wye connection because of the available suply


When was Delta Connection - Kenya - created?

The delta connection was founded in 1984 this was one of the four main skyteam. Also delta connection was founded to have middle population community. Also known as feeder flights.


What is delta of distance?

That means a difference between two distances.


How to calculate delta temperature?

To calculate the delta temperature, you will take the difference between the final and initial temperature.


Why does delta's connection draw high current?

For the same amount of power, a star or delta connection will use the same line current. However a delta connection supplies sqrt(3) times less current to the device on each of its connections because the voltage is sqrt(3) times more. The apparent contradiction comes about because in a delta connection each connection to the line is shared between two connections to the device (Historikeren 20-07-2015).