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About generators used in conjunction with the problem of com

2014-02-22 15:41      Click:

Reactive power compensation in a variety of methods, shunt capacitors due to the characteristics of its simple structure, easy and flexible installation methods , lower operating costs and low product prices , etc., has made it become the reactive power compensation used in leading products. Especially with the capacitor manufacturing techniques become more sophisticated , the quality level of life levels, and other indicators of reliability, safe operation can be greatly improved ; varieties and specifications are increasingly equipped to compensate for device design and production brought great convenience. Therefore, as the main application fields produced by the various sets of capacitor compensation and filtering devices are increasingly being used . Has gradually replaced the traditional synchronous condenser .

But the parallel capacitor also has its shortcomings: for example , only classification compensation fixed reactive power ( single precision determines the compensation capacitor capacitance of the capacitor group ) , but not continuous , linear compensation. In addition , the presence of harmonics in the system, but also may have parallel resonance inherent in the system reactance , so the harmonic current amplification ( up to the rated current of the times or even several times ) , resulting in a capacitor and associated components and wiring serious overloaded and burned .

Generator voltage regulator relies ( generator regulator plate ) to control the output voltage. The three-phase voltage regulator the output voltage , the voltage of its average value is compared with the requirements . Regulator to obtain energy from the internal auxiliary power generator , usually coaxial with the main generator of small generators, DC power transmitted to the generator rotor magnetic field excitation coil.  or rotating magnetic field is called the EMF of the coil current increase or decrease the size of the control stator winding . Determines the flux of the stator coil of the generator output voltage .

Generator stator coil resistance to Z said, including inductive and resistive portion ; generator force controlled by the rotor excitation coil AC voltage source E said . Assuming the load is purely emotional, the current I in the vector diagram hysteresis voltage U just 90 ° electrical phase angle. If the load is purely resistive , U and I will coincide or vector phase. In fact the majority of the load between purely resistive and pure sensibility. Current induced by the stator coil voltage drop I × Z represents the voltage vector . It is actually the two voltage vectors and the smaller , the voltage drop across the resistor with the phase I and 90 ° ahead of the inductive voltage drop . In this case, it happens with the U phase. Because the force must be equal to the internal resistance of the generator and the output voltage of the voltage drop and that the vector E = U and I × Z and a vector . The voltage regulator can effectively change the control voltage E U.

Now consider pure capacitive load instead of pure inductive load , the internal situation of the generator what happens . Then opposite currents and inductive load . Current I now leads the voltage vector U, the voltage drop across the internal resistance of the vector I × Z, also happens to be inverted. U and I × Z is the vector sum of less than U.

As the same time , and inductive load force E generated when a high capacitive load generator output voltage U, the voltage regulator must be significantly reduced rotating magnetic field . In fact, the voltage regulator may not be enough to fully regulate the output voltage range . All of the generator rotor continuously in one direction contains a permanent magnetic field , even if the voltage regulator is fully closed , the magnetic field of the rotor still have enough to charge the capacitor and the load voltage is generated , this phenomenon is called " self-excited ." The result is a self-excited or over-voltage is the voltage regulator shutdown, monitoring system is considered to be the generator voltage regulator failure ( ie, " Reed lost " ) . This situation will lead to either shut down the generator . The generator connected to the output terminal of the load , may be independent , or may be connected in parallel , depending on the timing of the automatic switch cabinet and work setting . In some applications , the capacitor compensation system power load on the generator is first accessed .

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