Step 1 introduce
In electrical engineering, the concepts of active power, reactive power, and apparent power are essential to understanding the behavior of AC circuits. These parameters play a key role in ensuring the efficient transmission and consumption of energy. On this page, we will explain these different types of powers and how to calculate them.
2. Active power (real electricity)
Active power, usually called real power, is a basic electrical parameter in watts (W). It represents the actual power consumed or generated by the electrical equipment responsible for performing useful work. Active power supply is the power supply for lighting, rotating motors, and running electronic equipment.
3.1 Calculation of the active power of a single-phase current
The active power calculation formula of a single-phase current motor is as follows:
P = u * I * pf
（PF = cos φ）
P = U * I * cos φ
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Location:
Active power (W)
U = voltage in volts (V).
I = current in amperes Aa).
φ = the difference between the phase angle of voltage and current.
Power factor
3.2 Calculation of Active Power of Three-phase Current
The active power calculation formula of a three-phase current motor is as follows:
p = 31/2 * U * I * PF
（PF = cos φ）
P = 31/2 * U * I * cos φ
Location:
Active power (W)
U = voltage in volts (V).
I = current in amperes Aa).
φ = the difference between the phase angle of voltage and current.
Power factor
3.3 Active Power Measurement
Measuring active power is usually done by using a device called a wattmeter, which directly reads the active power in the circuit.
3. Reactive power
Reactive power, named Q, is an important part of the AC power system. Its unit of measurement is volt-ampere reactive power (VAR). Reactive power does not perform any useful work, but it is very important to maintain the voltage level and support the operation of inductive loads, such as motors and transformers, and capacitive loa, ds such as capacitors.
3.1 Calculation of reactive power of single-phase current
The reactive power calculation formula of a single-phase current motor is as follows:
Q = U * I * sin φ
Location:
Reactive power (VAR)
U = voltage in volts (V).
I = current in amperes (A).
φ = the difference between the phase angle of voltage and current.
3.2 Calculation of Reactive Power of Three-phase Current
The reactive power calculation formula of a three-phase current motor is as follows:
Q = 31/2 * U * I * sin φ
Location:
Reactive power (VAR)
U = voltage in volts (V).
I = current in amperes (A).
φ = the difference between the phase angle of voltage and current.
The calculation of reactive power involves the triangular relationship composed of active power, reactive power, and apparent power.
4. Apparent Power Calculator
Apparent power is expressed by S, and the unit is volt-ampere (VA), which is the vector sum of active power and reactive power. It represents the total power flow in an AC circuit, including the power of doing work (active power) and the power of oscillating back and forth (reactive power).
4.1 Apparent Power Calculator Formula
When the actual power and reactive power of the motor are known, the apparent power can be calculated, which is usually recorded as S:
S = (q2 + p2)1/2
and
Apparent power (VA)
Q = reactive power consumption (VAR)
P = active power consumption (W)
apparent power calculator is similar to the hypotenuse of a power triangle, and its magnitude is the square root of the sum of the squares of active power and reactive power. In a three-phase power system, it is very important to balance active and reactive power, and it is very important to understand apparent power.