CRESPAC is a leading manufacturer of thermoformed food trays in the packing material industry. The company provides various types of PET resin packaging materials for major food companies in the North American, including outer packaging trays for meat and agricultural products. In addition, the company also provides mushroom plates in various colors and sizes for major mushroom factories in Latin American. The plastic machinery and thermoforming machinery used in various production processes of the company bring high efficiency to production, but also bring serious problems of power quality pollution. These power quality issues include lower power factors and higher harmonic distortion problems.
According to electric schematic diagram provided by the customer, the maximum load current on the project site is 6800A. After using a professional power quality analyzer to monitor the power quality on site for more than a week, it was found that there were serious power quality problems, including a power factor of 0.62, THDi 35%, and a significant instantaneous current imbalance in the system. The reason for this phenomenon is that the production equipment on the project site contains a large number of nonlinear loads, which result in a non-linear relationship between the current and the applied voltage, forming non sinusoidal currents and generating harmonics. In addition, same as many industrial companies, the high energy consumption devices widely used in the manufacturing process, especially the asynchronous motors used in polish machines and conveyor belts, as well as the unreasonable distribution of some power lines, have resulted in 3 phase imbalance loads on site, further exacerbating the generation of harmonics. If the 3 phase imbalance of current occurs frequently and is not dealt with, it will cause damage to the asynchronous motors.
After learning the detailed situation of the power quality on the project site, experienced technicians of Sinava Power Solution by sufficient communication with the technical personnel of the project party, formulated a comprehensive and effective customized power quality solution. The difficulty of the project lies in the fact that the on-site power factor is 0.62, but the target power factor is 0.98. For reactive power compensation equipment, the instantaneous current output is relatively large, which puts high demands on the equipment's heat ventilation. The harmonic content THDi 35% is an average value, and according to the analysis of professional instruments, there are some high harmonic order at 50th orders or above. In addition, there are issues such as high concentration of 7th, 9th, and 11th harmonics. In practise, there are certain technical difficulties in filtering out the 7th, 9th, and 11th order of harmonics in the electric system. Because according to the characteristics of the current sine wave, The active harmonic filter can easily cause current superposition when filtering the 7th, 9th, and 11th order of harmonics with the same output size but opposite directions. How to ensure the filtering effect and prevent resonance, and avoid causing instantaneous overload of current and damaging the harmonic filter itself, are all requirements for the equipment. Finally, in order to address the serious issue of three-phase imbalance on site, we have also reserved more sufficient compensation capacity for customers and changed the algorithm of the harmonic filter module. Fortunately, the power quality solution which Sinava customized for the project, consisting of three 500Kvar thyristor automatic switching capacitor cabinets and a 400A active filter hybrid compensation solution, was successfully installed and operated as expected.