Advantages n disadvantages of ac over dc?

Answer 1

AC electrical distribution systems can easily allow changes in voltage using Transformers. This gives AC electrical distribution systems a great advantage compared to DC.

By using transformers, AC power can be changed up to very high voltages for transmission and then changed down again to safer voltages for consumers to use, with comparatively very much less loss of power than DC.

AC has less copper loss (more heating effect) than DC and it's easier and cheaper to produce too.

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The voltage of AC can be easily changed while it's difficult to do so in DC.

Other Factlets

• AC is usually used for transmission because DC cannot be run through a transformer.
• Edison's original system was DC. It required many power generating stations because the voltage couldn't be stepped up/down like AC. This is why Westinghouse's (Well, Tesla's IIRC. Westinghouse bought it.) AC system lasted in the long run.
• Sometimes high voltage DC is used for transmission, but it requires special equipment at both ends.
• Semiconductor electronics require low voltage DC so your electronic devices have power supplies that change the high voltage AC to low voltage DC.
• A battery used to store electricity can only store and deliver DC. This is why the basic electrical system used in vehicles is DC.

Answer 2

Alternating current (AC) system is used in transmission where energy is needed in bulk power, such as house hold, commercial and industrial use. The capability to transform voltage and flow energy in two opposite direction is the advantage of Ac system over DC system.

Answer 3

The primary advantage of AC of DC power transmission is that power can be transferred farther (at "low" voltage). Equipment is often cheaper for AC vs. DC - such as breakers, which are designed to extinguish the arc caused by opening contacts due to the zero voltage crossing available in AC - this allows them to be built smaller than equivalent DC breakers. Stepping up / down voltage is simpler in an AC system as well, with a transformer.

DC transmission can be accomplished with two wires, instead of the typical three + neutral in three phase power. In fact, if the ground is cut, DC power can still be transmitting using the single line. DC power allows better control over power transmission - transmission is controlled by raising the voltage at one point vs. another. In an AC system, a voltage increase impacts power transmission, but phase angle also does. This is one reason why there is the Texas interconnect in the US (DC ties connected Texas to the US).

Answer 4

ac power can be readily stepped up and down via transformers. this is useful as we need to step up electricity to high voltages before sending them over long distances to save energy.

dc power is compatible with most appliances without the use of a diode (as most electronical appliances require dc to operate such as laptops, televisions etc...)

Answer 5

In most instances it is cheaper to use AC over DC, which is why it is so prevalent. But there are instances where the benefits of DC over AC outweigh this cost. Some benefits of DC over AC are listed below:

1. Direct Power Control

In AC systems, power is transferred from one location to another by changes in voltage magnitude AND phase angle. The changes in magnitude are usually not desirable and are small, so the main method of controlling power flow is by controling the phase angle relative to another location, which is not always possible. DC system power control is accomplished by raising the voltage at one point relative to another, which is much simpler.

2. Phasing

In AC systems, phase shifts can mean certain lines cannot be tied together. Two distribution transformers (Delta/Wye for this example) connected to the same highside line but with different phase angle shifts (say 30 degrees and 150 degrees) cannot have their lowsides tied together at the same time. If switching was required to take one of these transformers out of service, it would be necesssary to remove it (and all load connected to it) from service, then close switches to transfer the load to the in-service transformer. This is a simplistic example of why there are DC interconnections. In the USA there are three - the Eastern, Western, and Texas. States in the east and west created their own power grids, and when they came together on the eastern side of the Rockies, neither side wanted to turn off all power so they could be forced into sync. The only way to tie both grids together was to create a DC intertie.

3. Frequency

In DC system, the frequency is zero, thus no frequency variation to monitor. Connection will not also require synchronization.

4. Analysis

Analysis of AC system always involves complex numbers, while DC is only a real number (if you ignore time variations), thus simplifying the analysis.

5.Number of conductors.

A DC system requires only one conductor (power will actually return through the ground) as compared to two for AC systems. In special situations, AC can limp along on one conductor, but it will cause problems (single phasing of motors, for one).

If DC systems have the ability to transform voltage into various levels efficiently, the DC transmission system could be more efficient, stable, and easy to monitor.

Currently, the transformation of DC voltage into another level involves 3 steps:

1. AC to DC Rectification

2. AC to AC transformation, and

3. DC to AC Conversion

If compared to AC system voltage transformation, steps 1 and 3 are the added steps. Unfortunately, these steps incur heavy losses. However, modern technology converters/inverters have reduced the amount of loss. A 1000 MW, 230 KV AC - 450 KV DC/ 450 KV DC - 230 kV AC converter/inverter, for example, has a combine power loss of around 1.6%. AC/AC conversion through a typical modern power transformer is near 99.9% efficient.

The use of DC system in the transmission of power will be more prevalent if the added value of its' benefits is higher than the cost incurred from the additional equipment.

Answer 6

AC voltage can easily (and efficiently) be stepped up or down by use of a transformer. Since power is the product of current and voltage (V x A), high voltages can be used for long distance transmission, and since the current is relatively low, the resistance losses in the wires is low. The voltage can then be stepped down to safer levels for use at the destination. By contrast, DC can only be stepped down by using resistors which would experience huge power losses.

Answer 7

dc(direct current) is constant over all the time period.losses are less.less cable is required.

Answer

It depends what you mean by 'valuable'. Valuable usually means 'worth more', so it's difficult to figure out what you are asking.

Answer 8

The main benefit of AC over DC is the ability to transmit voltages over very long distances. Also with AC, the ability to manipulate the voltage through the use of transformers. This is a large bonus due to the many different voltages used through out the world.

Answer 9

1- Most advantageous fact is that AC can be stepped up and down from one level to other easily. Transformers available for this purpose are cheap, reliable and robust in design and construction. DC can't be stepped up/down easily and economically.

2- For long distance transmission with higher voltages(but not too long), AC is most economic but for too long like 1000KM transmission lines, DC is most economic.

3- AC resistance is always greater than DC resistance(1.2 to 1.5 times)

so Cu losses are more in AC.

4- In AC system, we get three phases(even we can get more), which is a desirable property as we can feed different areas with different phases and if any problem occurs only in single phase then other two will keep on working and total power cut will not occur in all areas connected to the same supply as will be the case with DC.

5-AC machines are cheaper and simpler in cost and design respectively.

6- In AC system we have to deal with reactive power and need to compensate it(extra effort and cost) but in case of DC there is no such requirement.

7-In AC system for the transmission of power, we need 3 or 4 conductors but in case of DC we need only 2 so it's cost effective.

8- In AC system, due to Skin Effect cross sectional area of conductors are more since current wave travels on the outer periphery of cross section up to skin depth but in DC it flows through entire area and so cost of conductor is less in DC.

Answer 10

advantage: can travel more distance

disadvantage: can create electrical and electro-magnetic interferences