It is known that a current of 1 a at A voltage in the electrical network 1 delivers power to 1 watt. But this ratio can be used to find power only in the constant values of the potential difference and current strength. Ie, when determining the power (P) in a DC network. To do this, use one of the following formulas, depending on the task parameters: P = I*U, P = I2*R, where I is the value of the DC current, U – voltage, R – resistance.
However, it is often required to determine the power in an alternating electric field in circuits sinusoidal current. Thus for full power of the circuit taking the product of the values of voltage and current in accounting for the phase shift between these values, i.e., the reactive and active components of power and power factor.
Find the active power of the alternating field. For this, in addition to current values, it is necessary to know the resistance (R) of the circuit. Substitute the given values in the formula P = I2*R and calculate the value. If in an electrical circuit there are several individual parts (resistors), determine the active power for each of them. Fold the values of the active capacity of the entire chain.
Calculate the reactive power of the AC circuit. It approximately describes the energy conversion processes in the fields of inductances and capacitances. And reactive power the active-inductive load element is a positive value, and conversely, negative when the active-capacitive nature of the load. This means that if the circuit inductor reactive power will have positive sign and the capacitive power capacitor – negative. To calculate the reactive power element of the inductor (RL) or capacitor (RS) use the same formula P = I2*R , where R is the resistance of the particular element. Sequentially calculate power for each element. Determine the total reactive power of the circuit. Fold values found, in this case, consider the sign of the reactive power of the capacitor: RR = Рл1 + Рл2 – RS.
Determine the full capacity of the AC circuit. It is associated with an active and reactive capacity by the following relationship: S = √(RA2 + PP2). Substitute into the formula the values of capacities and calculate the final result.