Tsananin Tafin Kasa | Mafiya na Daga da Karamin Yawon Siffo
Akwai duka biyu na system da ake amfani da su a electric circuit, wanda shi ne single phase da three phase system. A cikin single phase circuit, za a fi sanya phase kawai, ya'ni current zai tafi a kan wire kawai da kuma zai a baka path da take da neutral line don kammala circuit. Don haka, a cikin single phase, zai iya tafara kyakkyawa da power. A cikin wannan, generating station da load station za su bi single phase. Wannan shine system da ake amfani da ita tun daga zaman mai rike.
A shekarar 1882, an yi hakuri a cikin polyphase system, wanda ana iya amfani da phases da suka fi yawa don generating, transmitting da kuma load system. Three phase circuit shine polyphase system inda ake bayyana three phases tare da generator zuwa load.
Har phase na da phase difference da ta 120o, ya'ni 120o angle electrically. Saboda haka, daga total of 360o, three phases suna kammalawa da 120o each. Power a three phase system yana daidaita saboda dukkan three phases suna shiga a generating the total power. Sinusoidal waves for 3 phase system ana nuna a cikin karin-
Three phases zai iya amfani da su kamar single phase each. Saboda haka, idan load yana cikin single phase, zan iya tabbatar da phase kawai daga three phase circuit da kuma zai iya amfani da neutral as ground don kammala circuit.
Mimminka Three Phase Yana Da Ziyartar Da Single Phase?
Akwai abubuwa da dama da ke nuna mimminkinsu, saboda akwai albashi da ke da three phase system. Three phase system zai iya amfani da su kamar three single phase line, saboda haka zai iya taimaka a matsayin three single phase system. Three phase generation da single phase generation suna daidai a cikin generator saboda arrangement of coil in the generator to get 120o phase difference. conductor needed in three phase circuit is 75% that of conductor needed in single phase circuit. And also the instantaneous power in single phase system falls down to zero as in single phase we can see from the sinusoidal curve but in three phase system the net power from all the phases gives a continuous power to the load.
Hadi na lura, za a iya cewa akwai three voltage source connected together to form a three phase circuit and actually it is inside the generator. The generator is having three voltage sources which are acting together in 120o phase difference. If we can arrange three single phase circuit with 120o phase difference, then it will become a three phase circuit. So 120o phase difference is must otherwise the circuit will not work, the three phase load will not be able to get active and it may also cause damage to the system.
The size or metal quantity of three phase devices is not having much difference. Now if we consider the transformer, it will be almost same size for both single phase and three phase because transformer will make only the linkage of flux. So the three phase system will have higher efficiency compared to single phase because for the same or little difference in mass of transformer, three phase line will be out whereas in single phase it will be only one. And losses will be minimum in three phase circuit. So overall in conclusion the three phase system will have better and higher efficiency compared to the single phase system.
In three phase circuit, connections can be given in two types:
Star connection
Delta connection
Less commonly, there is also an open delta connection where two single-phase transformers are used to provide a three-phase supply. These are generally only used in emergency conditions, as their efficiency is low when compared to delta-delta (closed delta) systems (which are used during standard operations).
Star Connection
In star connection, there is four wire, three wires are phase wire and fourth is neutral which is taken from the star point. Star connection is preferred for long distance power transmission because it is having the neutral point. In this we need to come to the concept of balanced and unbalanced current in power system.
When equal current will flow through all the three phases, then it is called as balanced current. And when the current will not be equal in any of the phase, then it is unbalanced current. In this case, during balanced condition there will be no current flowing through the neutral line and hence there is no use of the neutral terminal. But when there will be unbalanced current flowing in the three phase circuit, neutral is having a vital role. It will take the unbalanced current through to the ground and protect the transformer. Unbalanced current affects transformer and it may also cause damage to the transformer and for this star connection is preferred for long distance transmission.
The star connection is shown below-
In star connection, the line voltage is √3 times of phase voltage. Line voltage is the voltage between two phases in three phase circuit and phase voltage is the voltage between one phase to the neutral line. And the current is same for both line and phase. It is shown as expression below
Delta Connection
In delta connection, there is three wires alone and no neutral terminal is taken. Normally delta connection is preferred for short distance due to the problem of unbalanced current in the circuit. The figure is shown below for delta connection. In the load station, ground can be used as neutral path if required.
In delta connection, the line voltage is the same as that of phase voltage. And the line current is √3 times of phase current. It is shown as expression below,
In a three-phase circuit, star and delta connection can be arranged in four different ways:
Star-Star connection
Star-Delta connection
Delta-Star connection
Delta-Delta connection
But the power is independent of the circuit arrangement of the three phase system. The net power in the circuit will be same in both star and delta connection. The power in three phase circuit can be calculated from the equation below,
Since, there is three phases, so the multiple of 3 is made in the normal power equation and the PF is power factor. Power factor is a very important factor in three phase system and some times due to certain error, it is corrected by using
