With electrical systems such as solar panel systems being used in a wide range of industries, more and more people are beginning to realize that in order to adapt to today’s times, it has become necessary to understand the basic electrical knowledge about electrical systems. Especially for a variety of common physical quantities of the units of measurement between the conversion method of a class of problems. In this article, we will introduce you to the meaning of volts-amperes, watts, and related units of measurement, as well as how to convert from volts-amperes to watts.
Before learning how to convert between the two, we need to understand the following physical quantities.
A watt is a unit of power. It is often used to describe how much energy an appliance requires to do its job. The higher the wattage, the more energy it requires to operate, and conversely, the lower the wattage, the less energy it requires to operate.
The volt is the unit of voltage in a circuit, abbreviated as V, and is often used to describe the number of charges passing through a circuit at the same time, and can therefore be used to indicate the “force” of the current in a circuit. The greater the number of volts in a circuit, the greater the force of the current in that circuit, and conversely, the smaller the number of volts, the less the force of the current in that circuit.
An ampere is a unit of current (I) in a circuit, abbreviated as ampere and symbolized as A. It is commonly used to describe the magnitude of the current in a circuit. From a microscopic point of view, it represents the amount of charge that passes through a section of a circuit in an instant, i.e., the rate at which current passes through a section.
Volt-ampere is a unit of circuit power, symbolized as VA, and is calculated by multiplying the circuit’s volt value by its ampere value:
1VA = 1V x 1A
That is, one volt-ampere represents the product of one unit of volts and one unit of amperage in a circuit.
It is worth noting that, although the volt-ampere and watt are the same unit of power, but the volt-ampere is only in DC circuits as a unit of measurement of real power, in AC circuits, the volt-ampere is the unit of measurement of the apparent power of AC circuits, and the watt is the unit of measurement of real power regardless of what kind of circuits are in.
In DC circuits, both the volt-ampere and the watt are units of measurement of circuit power, and can therefore be converted directly by multiples in the International System of Units. The conversion formula between watts and volt-amperes can be seen through the definitions of the two:
1VA = 1W
In AC circuits, although the volt-ampere and the watt are the same unit of measurement for power, they cannot be directly converted by multiples in the International System of Units because the volt-ampere is not the same unit of measurement as the watt in AC circuits. In order to learn how to convert the two, we first need to understand the difference between apparent power and real power.
Real power (P): is used to describe the actual use of electricity in the process of how much energy consumed by the physical quantity.
Apparent power (S): is used to indicate the size of the capacity of electrical equipment in the AC circuit.
The difference between the two is that the apparent power takes into account the power of all parts of the circuit, while the real power only takes into account the power of the resistive part of the circuit.
In order to convert volt-amps to watts in an AC circuit, we need to introduce an intermediate physical quantity, the power factor PF, which is the power factor of an AC circuit, i.e., a measure of the phase difference between the voltage and the current in the circuit. The greater the phase difference between the voltage and current in the circuit, the lower the power factor, the less efficient the circuit, and the less stable the overall system. The formula for converting the two in an AC circuit can then be derived as:
P (W) = S (VA) × PF
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