Difference between DC Power Supply and AC Power Supply

Application Specification

There are Direct Current and Alternating Current

There are two types of current, direct current (DC) and alternating current (AC).

Direct current is a method by which current always flows in a certain direction, like a river. It refers to the current obtained from batteries, storage batteries, solar cells, etc.

Alternating current, on the other hand, is a method of constantly switching between positive and negative, and the direction of the current is constantly changing. It is the current obtained from the generator and the socket.

Alternating current is also transmitted to the electricity generated by the power plant and then sent to the home.

Direct current has a constant voltage, and the current flows in a certain direction. In alternating current, on the other hand, the voltage changes periodically from positive to negative and from negative to positive, so the direction of the current changes periodically accordingly.

There is no better choice between direct current and alternating current, each has its advantages and disadvantages. Select various characteristics of current and power supply according to the purpose of electricity and equipment.

Characteristics of DC Power Supply

In alternating current, the direction of the current is always changing. Thus, for example, when a capacitor assembly or coil assembly is included in the circuit, the current flowing through the load will delay or advance the behavior of the voltage. However, for direct current, the direction of the voltage and current is always the same, so the behavior of the capacitor and coil is always the same. Therefore, with direct current, there is no advance or delay in the circuit.

Also, in alternating current, the direction of the current is switched, so not all of the power goes through the load, and the generated power just goes back and forth between the load and the power supply. This is called reactive power.

With direct current, the current always flows in one direction, so all the electricity passes through the load.

Therefore, no reactive power is generated and power can be used efficiently.

Another advantage is that direct current can be stored through batteries, capacitors, etc.

On the other hand, direct current also has its disadvantages. One of them is the difficulty of shutting off electricity.

Since direct current always applies a constant voltage, at the moment of interruption, especially at high voltages, there are problems such as arcing (sparks) or the danger of electric shock around.

In the case of alternating current, when the voltage changes from positive to negative and from negative to positive, the voltage becomes zero instantaneously. If targeted at low voltages, the current can be cut off more safely than the current.

In addition, when converting DC voltage, it needs to be converted to AC once and then back to DC. As a result, DC voltage converters are larger and more expensive than AC voltage converters.

Another disadvantage of direct current is that the underground pipes and insulators needed for transmission are severely corroded. Because the current always flows in the same direction as the DC, the corrosion of the transmission equipment will be aggravated by electrostatic induction and electrolytic corrosion. Direct current comes from stored things such as batteries, batteries and capacitors. Therefore, battery-powered products are compatible with direct current.

On the other hand, the power source of the average home is alternating current, while electronic devices such as personal computers and household appliances such as televisions use direct current. When operating such a device, the alternating current from the socket is converted into direct current through capacitors, etc., and used.

However, in data centers that primarily use direct current, DC power is becoming more common in order to reduce losses when converting alternating current to direct current.

Characteristics of AC Power Supply

In order to improve the efficiency of transmission for long-distance transmission from the power plant to the urban area, the transmission is carried out at an extremely high voltage of 600,000V (V). This is because low-voltage transmission can cause a lot of power loss. This is because if a wire (resistor) of the same length is energized for the same amount of time, heat will be generated proportional to the square of the current. Heat is energy that escapes to the outside, so it is a power loss.

For example, if you need 3000W (W) of power, the voltage of 100V requires 30A (ampere) of current, and the voltage of 1000V, 3A current is enough.

In other words, if the voltage is multiplied by 10, the current flow will be reduced to 1/10, and the power loss can be reduced to 1/10 squared or 1/100. Therefore, in long-distance power transmission, power transmission is carried out at very high voltages. Of course, the current voltage cannot be used in homes and offices. The voltage provided is 100,000V for large factories, 6600V for buildings, 200V or 100V for homes and businesses. Therefore, it is necessary to reduce the voltage of the power generated by the power plant depending on the region and location.

In contrast to DC, AC can be easily converted by transformers using transformers and is therefore suitable as an infrastructure power supply.

In alternating current, the time when the voltage becomes 0 comes periodically, so easy to lose power when energized is also an advantage. In addition, as with household power supplies (outlets), it can be used without distinguishing between positive and negative, which can simplify connecting devices and operation.

On the other hand, the voltage value of alternating current is constantly changing, and there is a time when the voltage becomes 0, so the heat required needs to be higher than the target voltage.

The AC voltage waveform is sine wave, and the maximum voltage is √2 times of the actual value. The insulation performance and device specifications must be higher than the effective value.

Alternating current is characterized by being greatly influenced by coils and capacitors. In coils and capacitors, a voltage is generated that causes the current to flow in the opposite direction of the current, resulting in a lead or delay in the circuit current.

The electricity generated and sent by power plants is alternating current. At the power plant, three waves with an alternating waveform offset of 120 degrees are emitted simultaneously. This electricity is called three-phase alternating current.

There are two types of AC, single-phase AC and three-phase AC, especially three-phase AC for high-voltage transmission. When sent to a household socket, it will be converted to a phase with voltage conversion.

Ac is used as a general power supply (outlet) and for motors that do not require fine control, such as vacuum cleaners and ventilation fans. On the other hand, motors such as air conditioners, washing machines and refrigerators are finely controlled by inverters without the need to use AC power directly.