Prevent the generation of self-excitation. In ensuring the compensation effect of the premise, the choice of the compensation capacitor lower, not higher. Because frequency vibration plate off the power, its speed can not be immediately reduced to zero, the variable frequency vibration plate capacitor winding discharge, the frequency conversion motor to get excited, it may cause short-term overvoltage. If large capacity, consequential over-voltage is high, which for more frequent start-stop frequency vibration plate, whose life has a certain impact. To prevent compensation arising from the excitation frequency vibration plate to happen, local compensation capacity of the capacitor should be chosen, but complementary.
Prevent resonance: the reactive power compensation capacity allocation, should prevent resonance RLC circuit. Generally can be used to adjust the capacity of the capacitor way to avoid harmonic generation. To further avoid reactive power compensation occurs when the parallel resonance. The formation of the capacitor into the grid, you should check the conditions of occurrence of the critical capacity of the parallel resonance. Installation of series reactors also prevent resonance generated.
Against over-voltage: frequency vibration plate with reactive compensation, will cause the capacitor voltage increases at the installation, when the compensation capacity is too large, the grid voltage increases more, even to the extent not permitted. National standards, shunt capacitor voltage value over the long-term frequency of no more than 1.1 times the rated voltage. For medium-sized asynchronous frequency vibration plate taken into account the effect of certain compensation, but there will be a higher overvoltage, then pressure-sensitive device can be used to limit overvoltages.
Prevent prolonged sustain voltage: For automatic switching of the inverter to be vibrating plate, or reversible operation frequency vibration plate, from forward to reverse state transition state time, the terminal voltage of the capacitor must be reduced to the rated peak (initial value ) voltage is below 10%, or increased due to self-excitation, the frequency of the vibration plate voltage will not be increased to the extent permitted. When using automatic switching, the cast, cut time interval should be greater than or equal to the capacitor discharge time.
