Shematic.net

Compensation Device of Reactive Constituent of the Power

Compensation Device of Reactive Constituent of the Power

The consumable electric power has two constituents: active and reactive. The reactive does not execute work. Asynchronous engines, transformers and other powerful devices are the basic sources of reactive power. For compensation of reactive constituent of the power condenser batteries are used. Condenser batteries works in the set algorithm depending on the size of reactive power compensating the reactive loading. Reactive power is determined in kVAr. An electronic block is the basis of compensating devices. An electronic block providing algorithm of switching on, for example: 1:2:2, 1:2:4, 1:2:2:2, 1:2:4:4 and etc, connecting condenser batteries 5 kVAr 10 kVAr, 20 kVAr, 40 kVAr, 50 kVAr.

Fig. 1 - a circuit through which it is possible to set any algorithm: , where x = 1; at = 1, 2; z = 1, 2, 4 – weight coefficients of algorithm. The minimum value of weight coefficient (x = 1) will correspond to the minimum stage of adjusting of condenser device (5 kVAr, 10 kVAr, 20 kVAr, 40 kVAr, 50 kVAr). The weight coefficient is set by groups on the four values. The first and second group has the value 1:1; 1:2, all other – 1, 2, 4, that provides possibility of any value of algorithm for watching and exact connecting of condenser devices and compensation of reactive constituent of power.

Fig. 1. Electronic block of device for compensation of reactive constituent of the power.

The measured value of reactive constituent of the power is compared to the set values of currents from weight coefficients on the operating amplifier U4. A signal from amplifier U4 acts on comparator U5, which create mode for 8-digit reversible meter U6, U7. A reversible meter gives signals for switch on / shutdown of weight currents to the field-effect transistors T1...T8 (chopping tension is less than logical item “1”) and a reversible meter gives signals for switch on / shutdown of the proper condenser battery Q1...Q8 (through amplifiers: transistor, low-power relay R1...R8, more powerful relay).

Is in error by:

where – digitizing error;

  – resistive loading error, relies on the type of the field-effect transistors and size of the resistors R;

– error measurement resistors R;

– temperature error of resistance TCR (temperature coefficient of resistance) of the resistors R.

If R = 27 kOhm, . Time of conversion relies on the speed of switch on / shutdown of relay, and also from time of condensers discharge. Time of conversion is set by frequency of pulse oscillator fm.

added 16.11.08 23:15:00 | looked over 4678 times