单相交流点焊电源功率因数的精确计算方法

借鉴电力系统关于非正弦电流电网功率因数的频域定义方法,考虑电流谐波分量和相位因素对有功功率的影响,应用快速傅立叶变换对电网电压和焊接电流信号进行频域分解,计算获得了准确的交流点焊电源功率因数.在交流点焊机上进行短路焊接试验时,采用文中提出的方法计算相应的功率因数.结果表明,改变点焊机二次回路臂长引起的功率因数变化规律与理论分析结果相符;相同控制角计算所得的功率因数值较传统θ角法所得值小,与电力系统采用频域法对非正弦电流电网功率因数的计量结果一致.试验结果初步证明了提出的计算方法是可靠有效的.

Precise calculation methods of power factor for single-phase alternating current spot welding machine

Collaborating with the definition of the power factor for the non-sinusoidal waveform, this paper adopted the Fast Fourier Transformation ( FFT) to analyze the spectrum of grid voltage and welding current, considered the influence of current harmonics and their phase shifts on the active power, eventually calculated and obtained the accurate power factor of an alternative current spot welding machine. The results showed good coincidence with the theoretical analysis when the power factor changed with the length of the secondary loop. With the same triggering angle of the silicon-controlled rectify-er ( SCR), the calculated power factor was smaller than that obtained by the traditional angle θ method, but was identical with the data which was measured by the power system. In conclusion, the proposed method is feasible and effective.