Power is a physical indicator. It identifies the work done over time to help measure energy change. Thanks to the unit of measurement of current power, it is easy to determine the high-speed energy flow of energy in any spatial interval.
Content
- Calculation and types
- Determination of active and reactive indicator
- Measurement value
- Calculation examples
Calculation and types
Due to the direct dependence of the power on the voltage in the network and the current load, it follows that this value can appear as from the interaction of a large current with a low voltage, and as a result of the appearance of a significant voltage with a small current. This principle is applicable to transformation in transformers and when transmitting electricity over great distances.
There is a formula for calculating this indicator. It has the form P = A / t = I * U, where:
- P is a measure of current power, measured in watts;
- A - current work on the chain section, calculated in joules;
- t acts as a time interval during which the current work was performed, is determined in seconds;
- U is the electrical voltage of the circuit section, calculated in Volts;
- I - current strength, calculated in amperes.
Electric power can have active and reactive indicators. In the first case, the power force is transformed into another energy. It is measured in watts as it facilitates the conversion of volts and amperes.
The reactive power factor contributes to the occurrence of a self-induction phenomenon. Such a transformation partially returns energy flows back to the network, due to which there is a displacement of the current values and voltages with a negative impact on the power grid.
Determination of active and reactive indicator
The active power is calculated by determining the total value of a single-phase circuit in a sinusoidal current over a desired time period. The calculation formula is presented in the form of the expression P = U * I * cos φ, where:
- U and I act as rms current and voltage;
- cos φ is the phase angle between these two values.
Due to the power activity, electricity is converted into other types of energy: thermal and electromagnetic energy. Any power grid with a sinusoidal or non-sinusoidal current determines the activity of the chain section by summing the powers of each individual chain gap. The electrical power of a three-phase chain section is determined by the sum of each phase power.
A similar indicator of active power force is the value of the transmission power, which is calculated by the difference between its fall and reflection.
The reactive indicator is measured in volt-amperes. It is a quantity used to determine the electrical loads generated by electromagnetic fields within an AC circuit. The unit of measurement for the power of the electric current is calculated by multiplying the root-mean-square value of the voltage in the network U by the alternating current I and the phase sine angle between these values. The calculation formula is as follows: Q = U * I * sin.
If the current load is less than the voltage, then the phase displacement is positive, if, on the contrary, it is negative.
Measurement value
The main electrical unit is power. In order to determine what the power of the electric current is measured in, it is necessary to study the main characteristics of this quantity. According to the laws of physics, it is measured in watts. In production conditions and in everyday life, the value is converted to kilowatts. Large-scale calculations require conversion to megawatts. This approach is practiced in power plants to generate electrical energy. Work is measured in joules. The value is determined by the following ratios:
-
1 Joule is equal to 1 Watt multiplied by 1 second; - 1 kJ = 1000 J;
- 1MJ = 1,000,000 J;
- 1 watt / hour = 1 kilowatt / hour;
- 1 kW * h = 1000 W * 3600 s = 3600000 J.
The consumer power force is indicated on the electrical device itself or in the passport to it. Having determined this parameter, you can get the values of indicators such as voltage and electric current. The indicators used indicate what the electrical power is measured in, they can act in the form of wattmeters and varmeters. The reactive power of the power indicator is determined by a phase meter, voltmeter and ammeter. The state standard of what current power is measured in is the frequency range from 40 to 2500 Hz.
Calculation examples
To calculate the current of the kettle with an electrical power of 2 kW, the formula I = P / U = (2 * 1000) / 220 = 9 A. The length of the 6 A connector is not used to power the device into the mains. The example given is applicable only when the phase and current voltage completely coincides. According to this formula, the indicator of all household appliances is calculated.
If the circuit is inductive or has a large capacity, then it is necessary to calculate the power unit of current using other approaches. For example, the power in an AC motor is determined using the formula P = I * U * cos.
When connecting the device to a three-phase network, where the voltage will be 380 V, to determine the indicator, the powers of each phase are summed up separately.
As an example, we can consider a boiler of three phases with a capacity of 3 kW, each of which consumes 1 kW. The phase current is calculated by the formula I = P / U * cos φ = (1 * 1000) / 220 = 4.5 A.
On any device, an indicator of electrical power is indicated. The transmission of large power volumes used in production is carried out over high voltage lines. Energy is converted using substations into electric current and is supplied for use on the mains.
Thanks to simple calculations, the power value is determined. Knowing its value, you can make the correct selection of voltage for the full operation of household and industrial appliances. This approach will help avoid burnout of electrical appliances and protect the power grid from voltage surges.
