Single phase and three phase are the two types of alternating power terminology for power generation, power transmission, and power distribution.
After the invention of the AC, the electric power is distributed to the uses in two different power variations, which is in single-phase power and three-phase power.
These 2 types of power supply are Will only occur in the ac power supply. the dc power supply is represented as two terminals, one is positive and the other is negative.
but the ac power supply is two types, the first one is a single-phase power supply and another is the three-phase power supply.
the single-phase power supply is represented in 2 terminals, the first one is a phase and the other is natural. but the output of the three-phase power supply is 2 different types.
1. three-phase 4 wire system
2. three-phase 3 wire system
the output of the three-phase 4 wire system is R Y B and N, the 3 wire system has only R Y B
what is phase in electrical
Definition: In electrical, the phase is called a specific spot at a complete sine wave at a specific time or in other words, it is defined as the position (0°degree to 359° degree) of point in time on a cycle of a waveform.
The phase difference means, the amount of phase angle difference between two or more waveforms.
In a single-phase wave, there is no importance for phase difference, but on the three-phase wave, 3 sinusoidal waveforms are present with different phases.
Between every three waveforms, 120° degree is the phase difference
the Comparison table between single and three phase
| Features | Single phase | Three-phase |
| Waveform | Single sinusoidal wave | Three sinusoidal waves |
| Wires | 2 two, phase and neutral N | 3 or 4 wire, R Y B and neutral N |
| Voltage range | 120V to 240V | 400V to 480V |
| Phase difference | No phase difference | 120° degree phase difference between each phase |
| Power | Moderate range | Higher compare to single phase |
| Losses | High losses | Low lower losses compared to single phase |
| Efficiency | Low | High |
| Power failure occurs | High | Low |
| cost | High | Low |
| Applications | Domestic applications | Domestic and industrial applications |
Wave shape of single phase and three phase
The single phase has a single sinusoidal shaped wave and three-phase have the same sinusoidal wave, but each three have three different phase variations.
the Phase difference between three phase and single phase
In a single phase, we don’t have any phase difference at the output, but at three phase wave, there is a phase difference of 120° degree is noticed at the signal, this is due to the method of power generation of 3phase.
Voltage rating of single phase and three phase
The voltage rating of both single phase and three-phase power is purely based on the distribution basis, in India, 230v is the standard single phase voltage rating with 50Hz frequency and 400v on three-phase power at 4 wire.
But in America, the single phase voltage is 120v with 60Hz frequency, and three phase power had a range of 240v to 480v at 3 and 4wire.
The voltage rating of single phase and three phases is different at each country is like an adaptation, they adopt a standard voltage value and this will be reflected in the electrical products produced at each country.
Generation of single phase and three phase
The single phase power is generated in a generator or alternator, which having a single bar magnet rotating inside a single coil shaped loop of wire as shown in figure(a). As when the magnet rotates, the magnetic line form at the machine gets cut and the single phase voltage is produced.
The three phase power is also generated inside the alternator as shown in figure(b), but this time the machine consist of three single phase windings, at the 360° circle cross-section of the generator, the stator is windings are separated with an angle of 120°, this is the reason why the 3phase power had a 120° phase difference.
Conductors required at single phase and three phase
The conductors required at single phase and three phases are very much different, at each of the processes generations, transmission, and distribution, the three phases need more conductors.
The higher required on the three phases is due to the reason, they handle more power than the single phase.
Wires used on single phase and three phase
The wires used at single phase power is only 2, +ve and –ve, but at three phases, the wired used is three or four at different systems, R, Y, B, and neutral N.
R stands for red, Y stands for yellow, B stands for blue, and common ground or neutral fourth wire.
The figure shows the voltage values between each R, Y, B, and N connection, between two phases that is R-B, R-Y, and B-Y, the voltage value is 440v, and the voltage between one phase and neutral N is 220v.
Circuit complexity of single phase and three phase
In the case of circuit complexity of single phase and three phases, the three phases had more complex circuits than single phase, this is because the three phases are capable of handling higher power value on more wires.
Power transferring capability of single phase and three phase
The power transferring capability is the amount of electrical power transfer from one place to another, the 3phase power had higher power handling ability than single phase, due to this reason three phases had more powerful applications than single phase.
Losses at single phase and three phase
In every electrical current carrying system, there is a proper value of power loss within the conductor, when the compare the power losses between single phase and three phases, the single phase maximum power losses value than three phases.
Expenses on single phase and three phase
Economically three phases are expensive than a single phase on all the stages, generation, transmission, and distribution, mainly the cost difference of 3 phase power handling device is way different from a single phase.
And the conductor used to transmit the three phases is three times higher than the single phase.
Maintenance of single phase and three phase
The maintenance cost is higher for 3phase power, but the maintenance need for three phase power is lesser than a single phase.
When we at the maintenance, the single phase needed to been fully shut down, but on three phases, even a fault is on one phase, other two-phase will deliver power for the loads.
the main Application of single phase and three phase
The main application of single phase power is at domestic uses like home and other applications need lower power, but the applications like heavy pieces of machinery at factories and companies, need the three phase power system.
Ideal applications of single and three phase
The ideal applications of single phase power at domestic systems are on heating and lighting and three phase power ideal applications are the heavy power motor on factories.
How to convert a single phase to three phases and vise versa
image source = plantengineering
Both the conversions are possible that is single phase to three phases and three phases to single phase, but it is not a device which is to for the conversion.
Several methods are available for the conversion process, the components include in the systems are meters, transformers, motor or generator, and transmission cables.
