Apparent power for the electric motor refers to the product of the effective value of voltage and the effective value of current in the AC motor circuit, represented by the symbol S, and the unit is volt-ampere (VA).
Figuratively speaking, apparent power is like a water pipe, which represents the flow of water in the water pipe, but it does not mean that all the water is effectively used.
Relationship between apparent power, active power and reactive power
Apparent power: represents the total power flow in the circuit, including active power and reactive power.
Active power: represents the power actually consumed in the circuit, used to do work.
Reactive power: represents the part of the energy stored in the circuit that oscillates back and forth between the power supply and the load, and does not represent the actual power consumed.
Power triangle
In the power triangle above:
S represents apparent power
P represents active power
Q represents reactive power
φ represents power factor angle
The power factor cosφ = P/S, which represents the proportion of active power in apparent power. The closer the power factor is to 1, the higher the power utilization rate.
The significance of apparent power
Reflecting the capacity of the circuit: Apparent power reflects the capacity of the circuit, that is, the maximum power that the circuit can withstand.
Basis for selecting electrical equipment: When selecting electrical equipment such as transformers and cables, it is necessary to select the appropriate capacity based on the apparent power of the load.
Evaluating the quality of power: The size of the power factor reflects the quality of power. The lower the power factor, the greater the reactive power and the greater the impact on the power grid.
Factors affecting apparent power
Load nature: Inductive loads (such as motors) will generate reactive power, resulting in apparent power greater than active power.
Power supply voltage and frequency: Changes in power supply voltage and frequency will affect apparent power.
Apparent power is an important indicator for measuring the total flow of electrical energy in a circuit. It is closely related to active power and reactive power. Understanding the concept of apparent power is of great significance for correctly selecting electrical equipment and improving the efficiency of power utilization.
Post time: Feb-08-2025