Electricity: 1 Phase Or 3 Phase. Why not 2 Phase?
Why is there no 2-phase electric power? I had asked this question to my professor back in the days when I was a student of electrical engineering.
In this article, I’ll explain the basics of power systems and try to answer the question. Let’s start.
Electric Power Systems: Why No Two-Phase Power?
The concept of electrical power systems is essential to modern life, fuelling everything from our home appliances to colossal industrial machinery.
While most are familiar with single-phase and three-phase power, the notion of a two-phase power system may seem foreign or non-existent. It's worth asking, "Why is there no two-phase power?" Let's delve into the details.
Overview of Electric Power Systems
Electrical power systems primarily come in two formats: single-phase and three-phase.
A single-phase power system is common in residential applications, providing power to light bulbs, small appliances, and other household equipment.
In contrast, three-phase power is typically used in industrial and large commercial settings, supplying power to large motors and heavy-duty equipment.
The Enigma of Two-Phase Power
Now, what about two-phase power?
In theory, a two-phase power system is possible and was even used in the early days of electrical power distribution. This system consisted of two alternating currents (AC), typically offset by 90 degrees of phase.
However, it has largely become obsolete for several reasons.
The Complications of Two-Phase Power Systems
The main issue with a two-phase power system is the complexity and costliness of its implementation.
It requires four wires: two for each phase and a neutral. As such, it tends to be less efficient than three-phase systems, which deliver more power using fewer wires, thereby saving on installation and operating costs.
The symmetry in a three-phase system also provides another advantage. With equal loads, the current in the neutral wire is zero, which allows us to use a smaller neutral wire or sometimes to eliminate it altogether.
However, this is not possible in a two-phase system.
The Superiority of Three-Phase Power
The design advantages of the three-phase power system over a two-phase system are significant.
A three-phase system provides a smoother power waveform, leading to more efficient operation of motors and less wear on equipment. It can also transfer more power over long distances with less voltage drop.
This means three-phase power is more efficient, effective, and economical. It also provides a self-starting capability for motors, which a two-phase system doesn't offer.
This is one of the main reasons why three-phase systems are the standard for large-scale industrial applications.
The Evolution of Power Systems
While two-phase systems were used in the early days of the power industry, as our understanding of electricity evolved, we have seen a shift towards more efficient systems.
The three-phase system has emerged as a superior choice due to its unique characteristics and advantages.
Although two-phase power systems are not commonly used today, their existence and history offer a fascinating insight into the evolution of our power systems.
They also demonstrate our continuous journey towards efficiency and sustainability in the world of electrical power.
Concluding Thoughts
To wrap up, while two-phase power systems are technically possible, they are practically redundant due to the efficiency and effectiveness of single-phase and three-phase systems.
The evolution of power systems has led us towards the optimization of resources and the sustainability of electrical power for a multitude of applications.
Let me know if that answers your question.
Replies
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PraveenKumar PurushothamanActually, 2 Phase Power exists... but they are not so efficient... Please see Two Phase Electric Power. 😀
It has an angle deviation of 90° and three phase are 120°! 😀 -
shubhankaractually the losses are less and efficiency is optimised (i.e max) in three phase system and the economics part is well taken care of a compared to 2 phase or other multiple phases excluding 3 phase
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narayana murthy
hey who told you that 2 phase is not using by my knowledge we are using 2 phase in railwayssrinudamagenerally we heard about single phase electricty and three phase why not two phase -
PraveenKumar Purushothaman
Hey NM, thats something new to hear... How is it possible in rlys???narayana murthyhey who told you that 2 phase is not using by my knowledge we are using 2 phase in railways -
shubhankarhuh? two phase in railways? railways employ dc series motor commonly or ac series very seldom. if only ac supply is to be used then 11 to 16 kV is used..can you explain the two phase system please. the two phase which i think is the main winding and the other one is the auxillary starting winding
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narayana murthyactually i don't know much about them while explaining about 3 phase to 2 phase conversion our sir told how we do it and there apps then i asked as "sir,where we use 2 phase supply"
then he replied as we use them in railway power on supply to the lines -
Chandrakiran2 phase supply have very little applications in transformers (scott connection) and used in 2 phase Induction Motors ( used in servomechanisms ranges from watts to few hundreds of watts) also 2 phase Induction drive is used in some ac tachometers as generators to measure angular velocity
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zenith999Why three phases? Why not two phase? In 1-phase and 2-phase power, there are 120 moments per second when a sine wave is crossing zero volts. In 3-phase power, at any given moment one of the three phases is nearing a peak. High-power 3-phase motors (used in industrial applications) and things like 3-phase welding equipment therefore have even power output. And we can reduce current in each phase when we increasing the phases but better to go for 3 phase because in view of good economical insulation cost, maintainace, efficiency and power transmission.
however some special applications runs with two phase and higher than 3 phase they are specially used in industrials.
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