Difference Between DC Power And AC Power - Matsusada Precision

AC, with its cyclic positive and negative voltage, has the following advantages and disadvantages.

Advantages

• Less power loss due to high voltage transmission
• Easy to transform
• Easy to shut down while power is flowing
• No need to worry about positive and negative voltage

Disadvantages

• Requires a higher voltage than the target voltage
• Affected by coils and capacitors
• Not suitable for ultra-long distance transmission

Especially when transmitting power over long distances, such as from a power plant to an urban area, a very high voltage of 600,000 V (volts) is used to improve transmission efficiency. This is because power loss is much greater when power is transmitted at low voltage. This is because when electricity is applied to a wire of the same length (resistance) for the same amount of time, heat is generated in proportion to the square of the current. Since heat is energy that escapes, it is a power loss. For example, if you need 3000W (watts) of power, if the voltage is 100V, you need 30A (amperes) of current, but if the voltage is 1000V, you only need 3A of current. In other words, if the voltage is increased by a factor of 10, the amount of current will be reduced to 1/10, and the resulting power loss can be reduced to 1/100, or the square of 1/10. For this reason, very high voltages are used for long-distance transmission. Of course, the voltage as it is cannot be used in homes and offices. The voltage supplied is 100,000V for large factories, 6600V for buildings, and 200V or 100V for homes and offices. Therefore, electricity sent from a power plant needs to be lowered in voltage to suit the region or location. Compared to direct current, alternating current can be easily transformed by transformers using transformers, making it more suitable for power supply as infrastructure.

Another advantage of AC is that it is easy to shut down while power is being supplied since the timing at which the voltage drops to zero comes periodically. It can also be used without distinguishing between positive and negative, like a household power supply (outlet), which simplifies the connection and operation of devices. On the other hand, AC requires a higher voltage than the target voltage for the required amount of heat because the voltage value is always changing, and there are times when the voltage goes to zero. The waveform of AC voltage is sinusoidal, and the maximum voltage is √2 times the running value. Insulation performance and equipment specifications must be higher than the effective value. Another characteristic of AC is that it is strongly affected by coils and capacitors. Coils and capacitors generate voltages that cause the current to flow in the opposite direction of the current direction, causing the current in the circuit to advance or lag. The electricity generated and sent to a power plant is alternating current. In a power plant, three waves of AC are sent out at the same time, with the waveform of the AC shifted by 120 degrees. This type of electricity is called a three-phase alternating current.

There are two types of AC: one-phase AC and three-phase AC. A three-phase AC is used especially for high-voltage power transmission. When it is sent to a household outlet, it is converted to one phase along with the voltage conversion. AC is used in general power supplies (outlets) and is used as-is for motors that do not require delicate control, such as vacuum cleaners and ventilation fans. On the other hand, motors for air conditioners, washing machines, refrigerators, etc., do not use AC power as it is, but use inverters for fine control.