What is the difference between a single phase and a 3 phase circuit?

Answer 1

Single phase power has a sine wave voltage that crosses zero before reversing its polarity. In the region near the zero-crossing there is not much power. At zero there is none at all. So single phase loads often need some trickery to deliver output in this area. Often it is just the inertia of the motor or appliance. Three phase power is always delivering power on one of its phases, and is thus preferred for generators, motors, machines and appliances that use lots of power. If the application is large power, or small power with weight restrictions (like automobiles!) Three Phase is preferred. DC (Direct Current) is the next step up for smooth high-power devices but requires rectification, regulation and smoothing to be useful.

Another problem with DC is that, for efficient long distance transmission, it cannot be simply converted to much higher voltages than the voltage at which it was generated at the power station. Similarly DC cannot be transformed down to safer, much lower mains voltages for use by consumers.

AC (Alternating Current) is used for high power generation and distribution because it can easily be transformed, using Transformers, to achieve very efficient power transmission over very long distances and can then be transformed down to low voltages for distribution to consumers. Two phase, and higher multi-phases are also used but very rarely.

Answer 2

Single phase power has a sine wave voltage that crosses zero before reversing its polarity. In the region near the zero-crossing there is not much power. At zero there is none at all. So single phase loads often need some trickery to deliver output in this area. Often it is just the inertia of the motor or appliance. Three phase power is always delivering power on one of its phases, and is thus preferred for generators, motors, machines and appliances that use lots of power. If the application is large power, or small power with weight restrictions (like automobiles!) Three Phase is preferred. DC (Direct Current) is the next step up for smooth high-power devices but requires rectification, regulation and smoothing to be useful.

Another problem with DC is that, for efficient long distance transmission, it cannot be simply converted to much higher voltages than the voltage at which it was generated at the power station. Similarly DC cannot be transformed down to safer, much lower mains voltages for use by consumers.

AC (Alternating Current) is used for high power generation and distribution because it can easily be transformed, using Transformers, to achieve very efficient power transmission over very long distances and can then be transformed down to low voltages for distribution to consumers. Two phase, and higher multi-phases are also used but very rarely.

Answer 3

Power stations commonly produce electric power as three-phase ac (alternating current) which is then distributed around the country in that form.

Heavy industrial electric motors run on three-phase services, as do many other types of factory and commercial electrical equipment such as deep-freeze storage units, large air conditioning units, very big ovens, etc.

Homes and offices generally run on single-phase electricity services which are derived from three-phase by using transformers.

For more information see the answers to the Related Questions shown below.

Answer 4

To answer this question in technical detail: a three-phase system is sourced from a three-phase alternator with a stator having three armature coils, each displaced from each other by 120 degrees. As the field rotor spins, it induces a voltage into each coil in sequence, making each voltage 120 electrical degrees apart.

The alternator's windings are connected together in such a way that only three conductors, called line conductors, leave the machine for high-voltage transmission/distribution via numerous three-phase transformers. The potential of each line conductor is displaced from each other by 120 electrical degrees.

To obtain a single-phase supply, a single-phase load is connected between any two of the three line conductors.

The main advantage of three-phase distribution is that, for a given load, a three-phase system uses less volume of copper (wires, transformer coils, etc.) than a single-phase system. Therefore three-phase systems are more economical than single-phase systems.

Providing three-phase services in residential buildings is unusual in most countries (especially in USA and Canada) but it has become quite standard in some countries, such as, say, Cyprus and has also become common for new homes built in Sweden and several other Northern European countries, with the exception of the UK and the Republic of Ireland, where it is usually only available to industrial sites.

Other answers

Three-phase is much more costly to install, but is much more efficient for high horsepower motor loads. Talk to your electric utility supplier. They may not even have three-phase service available to your location. Generally speaking it isn't available except in industrial areas.

Three-phase supplies are widely used for light commercial, such as stores, plazas, etc. and three-phase is widely used as the main feed for large residential buildings, such as large condos, apartment buildings. Only single phase is brought to the actual dwelling units but having three-phase brought to the building allows for more efficient water boilers to be used and also to supply the large motors used for elevators, etc.

<><><>

To illustrate the typical services available from some energy utilities:

A single phase 120/240 volt 100 amps service can provide 24000 watts of power. The largest single phase motor available is approximately 10 HP.

A typical 3 phase 120/208 volt service at 100 amps can provide 35984 watts of power. 3 Phase motors are available up to 3000 HP.

There is a 240 volt 3 phase service available, though is rarely used, and is only for industrial applications, so is not useful as an illustration.

There are several websites that explain three-phase theory. Maybe the math is a bit more than you need, but their explanations are good.

Answer 5

It is an over current, over load, three pole device used for protecting a three phase load. The breaker will have one common trip handle that opens and closes the three poles simultaneously. If one leg of the three phase load trips the breaker all three legs will be de-energized.

Answer 6

Because a three-phase system needs half the amount of wire to transmit power compared to three single-phase systems.

With a balanced three-phase system the three live wires are phased so that the sum of the currents is always zero, which means that if the three neutral wires are combined, the current in the neutral is zero. Therefore the original three neutral wires can be removed, leaving only the three live wires.

In practice a neutral wire is still included in three-phase four-wire systems when the load is potentially unbalanced, as for example in neighbouring houses which use different phases of a three-phase system for their individual single-phase supplies.

Answer 7

It consists of three phases and the voltage is alternating one.............