Voltage Waveform Distortion of Power Generating Sets

Oct. 19, 2021

The ideal waveform of the output voltage of the generator set should be a sine wave, but its actual waveform is not a real sine wave. It contains not only the fundamental wave, but also three or more higher harmonics. The generator set excited by the third harmonic is particularly serious. The percentage of the root mean square value of each harmonic modified to the fundamental effective value is called the voltage waveform distortion rate. Generally, the waveform distortion rate of no-load rated voltage of generator set shall be less than 10%. If the distortion rate of voltage waveform is too large, the generator will heat seriously, the temperature will rise, and the insulation of the generator will be damaged, affecting the normal working performance of the generator set


Adjustment range of no-load voltage of power & generating sets: when the unit operates stably, its no-load voltage shall be able to be adjusted within a certain range, which is due to a certain cable voltage drop between the unit and electrical equipment. The unit shall ensure that the end of output cable still has normal working voltage under certain load. Generally, the no-load voltage adjustment range is 95% ~ 105% of the rated voltage. For example, when the rated voltage of a unit is 400V, the no-load voltage adjustment range is 380 ~ 420v.


power generators

Voltage thermal offset: when the ambient temperature and the temperature of the generator set rise, the permeability of the generator core decreases, the DC resistance of the winding increases, and the circuit element parameters will change, resulting in the change of the output voltage of the generator set. This phenomenon is called voltage thermal offset. Generally, the voltage thermal offset of the unit is expressed as the percentage of the unit voltage change caused by temperature rise in the rated voltage, which is generally not allowed to exceed 2%


Voltage waveform distortion rate: The ideal waveform of the output voltage of the generator set should be a sine wave, but its actual waveform is not a true sine wave. It contains not only the fundamental wave, but also the third and more high-order harmonics, and the third-harmonic excitation The generator set is particularly serious. The percentage of the root mean square value of the effective value of each harmonic to the effective value of the fundamental wave is called the voltage waveform distortion rate. In general, the distortion rate of the no-load rated voltage waveform of the generator set should be less than 10%. If the voltage waveform distortion rate is too large, the generator will generate serious heat, and the temperature will damage the insulation of the generator, which will affect the normal working performance of the generator set.


Steady state voltage regulation rate: steady state voltage regulation rate refers to the deviation degree of the stable voltage of the unit after load change from the rated voltage of the unit at no-load, expressed in percentage. That is, the percentage of the ratio of the difference between the unit output voltage and the rated voltage to the rated voltage. The steady-state voltage regulation rate is an important index to measure the terminal voltage stability of the generator set. The smaller the steady-state voltage regulation rate is, the smaller the impact of load change on the terminal voltage of the unit is, and the higher the stability of the terminal voltage of the generator set is.


The steady-state voltage regulation rate is different under different loads. Under inductive load, the stable voltage after load change is lower than the no-load rated voltage. Under capacitive load, the stable voltage after load change is higher than the no-load rated voltage. The deviation from the no-load rated voltage depends on the regulation capacity of the excitation regulator. The stronger the regulation capacity is, the smaller the deviation value is, the smaller the steady-state voltage regulation rate is, and the more stable the terminal voltage of the unit is.


Guangxi Dingbo Power Equipment Manufacturing Co.,Ltd is a factory of electric generators, including open type generator, silent generator, canopy ggenerator, container generator and trailer generator etc. If you have purchasing plan recently, welcome to contact us by email dingbo@dieselgeneratortech.com, we will reply you at any time.

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