Reactive power of current can be received only in chains with alternating current in which there are inductance coils, condensers or that and another. In most cases reactive power does not perform useful work, and is spent for generation of electromagnetic fields. Power factor which is designated by Cos(φ) is specified in many devices. With its help it is possible to calculate easily reactive power, knowing consumed by the device power. If there is no such coefficient, it can be calculated independently.
It is required to you
- - value of power factor;
- - tester.
Instruction
1. For calculation of reactive power of the electric device attentively study its documentation In it the power factor of Cos(φ) has to be specified. By means of a tester measure the power consumption of the device, then from number 1 take away power factor, and increase the turned-out number by the measured power (Pr = P • (1 Cos(φ)). Reactive power of the device will also be result of calculations. In some devices the considerable reactive power develops, for example, in the arc furnace or the welding machine of alternating current its value can reach 40% of rated power.
2. If in the device the value of power factor is not specified, calculate reactive power independently. For this purpose, by means of the tester which is adjusted in the voltmeter mode measure voltage drop on the device, effective value. Learn the frequency of alternating current in network where connection the device, for standard household network this value is 50 Hz.
3. Switch a tester to measurement of inductance and learn its value for this device in Henry. After that switch a tester to measurement of electric capacitance and learn it, having expressed in Farads. In both cases connect a tester parallel to the device, to its clips.
4. Calculate reactive resistance for this purpose: 1. Increase number 6.28 by the frequency of current and value of inductance, inductive resistance XL=6.28•f•L. 2. Number 1 will be result divide into 6.28, current frequency in networks and electric capacitance of the device, the capacitance of XC =1 / will be result (6.28•f • æ). Find reactive resistance, having put the results received in subparagraphs 1 and 2. 4. Find reactive power, having divided tension square into the reactive resistance of Pr = U²/Rp. Thus, reactive power depends on current frequency in network, inductance and electric capacitance in loadings.