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Why only three phase system is used in power generation?

Hello friends, in today’s post, we will discuss why we use only three-phase system in electrical power generation and why we don’t use four, five, or single-phase systems.

If you are asked in an electrical interview, you can say in one line that we do not use single-phase, two-phase, four or five-phase in electrical power generation, only three-phase is used, it has two reasons.

  1. Three-phase system is the most efficient.
  2. Three-phase system is more economical than another phase system.

power plant

But Friends, If you are asked in the interview how the three-phase system is more efficient and economical than other phase systems such as single-phase, four-phase, etc?

So for what you have to answer, we will understand by comparing the three-phase system with different phase system.

What is the Difference between 1 phase and 3 phase?

Friends, if we talk about single-phase and three-phase systems, we should know that if we do transmission from our single-phase, we need two-conductor wires for transmission. There is one wire phase and one wire neutral. Inside single-phase, we cannot transfer power without a neutral wire.

single phase vs three phase

If we talk about three-phase, we need a total three-phase wire R, Y, B for transmission. Within a three-phase, three wires can send three times more power than single phase.

If we want to send this same power from single-phase, we need 6 conductors. Because inside a single-phase, we have to add a neutral wire with every phase wire. So total 6 conductors will be required.

Now, if we use six conductors, then there will be these losses:

  1. Using six conductors will increase our cost, due to which our system will not be economical.
  2. Due to 6 conductors, our voltage drop also increases. Because the resistance of our 6 wire will also become 6 times which will drop 6 times more voltage. But in a three-phase system, we use only three wires, so our resistance is less, and voltage drop will also be less.
  3. Friends, due to having six conductors, our transmission loss (I2R) also increases. So if we use a three-phase system, our losses will also increase.

Friends, we have discussed the difference between single-phase and three-phase and why three-phase should be used instead of single-phase. Now we will talk about why we did not select a single-phase system instead of a three-phase?

What is the Difference between 2phase and 3phase?

Friends, if we talk about two-phase transmission, we also need three conductor wires for transmission from two-phase. Two wires are for phase and one wire is neutral.

two phase vs three phase

With two-phase, we can transmit double power as compared to single-phase. Three conductors are used in two-phase, same if we talk about three-phase, then we can transmit three times the power as compared to single-phase and use three conductor wire in three-phase.

Because friends, inside three-phase we do not need to send neutral, whereas inside two-phase we also have to connect neutral wire. This is one of the main reasons that we have used three-phase instead of two-phase for electrical power transmission.

Friends, now this question come to your mind why  we don’t use more than three-phase like four-phase or five-phase. Friends, you will think that this question is very difficult, but we will explain it in a very simple way so that if you are asked in an interview or exam, then you can quickly answer.

Why more than 3 phase not taken?

Note: We have to take neutral wire along with phase wire in all the phases below three-phase, such as single-phase or two-phase. But in three-phase or above three-phase, we do not need a neutral wire because the nature of our system is such that we do not need neutral wire in it.

Friends, now the question comes that in four, five or six-phase neutral wire is not need and we can send more power than three-phase, yet we don’t use four-five or six-phase, we use only three-phase. Why is three-phase used in electrical power generation and transmission?

transmission line

The reason for using three-phase is simple. When we shift from single-phase, to three-phase, then we get two benefits.

  1. Transmission loss directly reduced by 50%. Mean in three-phase losses directly reduced by 50% compared to single-phase and two-phase.
  2. The transmission voltage drop was also 50% reduced.

But friends, when we increase phases like four, five or six-phase, we saw that the benefits we were getting by shifting from single-phase to three-phase, we didn’t get the same benefit by shifting from three-phase to four or five-phase.

power transmission line

Example: if we transmit from five phase instead of three-phase, then we need five conductor wire. Five phase will be able to transmit two times more power than three-phase. But if we talk about different advantages such as:

There is no reduction in voltage drop or transmission loss. Friends, we did not get any extra benefit. But due to taking more phases, our system became very complex.

why three phase used

If we use four, five or six conductors instead of three, then our system will become more complex. Apart from this, the cost of our system will also increase a lot. Because if we take five phases, we have to do five winding in transformer, apart from this, a separate system will be added to the circuit breaker for five-phase system.

Meaning that all the things will have to be connected extra. Due to this our transmission cost will increase. Friends. If we get some extra benefits, then we do not have much problem with increasing the cost. We all want that if we are spending some extra money, then we should also get some extra benefits.

But friends, if we increase phase above three-phase, then we do not get any extra benefit, and our cost also increases. In three-phase, our system remains simple, not too complex, and costs less than four or five phases.

So we prefer to use three-phase in electrical power transmission.

We hope that you understand. If still any doubt or question remains then feel free to ask in comment section or you can ask this question on Instagram Electrical Dost”

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