Comparison of VSI and PWM drives in an aluminum rolling mill ingot preheating application

Rising concern about work environments and power system efficiency has prompted careful evaluation of adjustable-speed drive applications. A case study is presented from data collected in a large industrial facility. A brief description of the process precedes comparisons of pulse-width modulated (PWM) variable-frequency drives to six-step voltage source (VSI) variable-frequency drives on a variable-torque load. The two types of drives are installed in similar systems. Motor acoustic noise and harmonic current injection into the power distribution system are examined. Test methods and results are discussed.<
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