Capacitors Near Loads? The Engineering Viewpoint

Since the National Electric Code has dropped rules for capacitors at motors, the electrical engineer´s responsibility has been established. Nevertheless, the Code´s 1981 edition suggests a simplified rational method of selecting capacitor size that is discussed here. The electrical engineer is assumed to understand that the purpose of applying capacitors is not merely to take care of an individual motor. Rather, it is to reduce to an economical level the vars carried by the local supply circuit and the whole plant. The most economical safe effective ways to improve power factor within the plant distribution system are reviewed. Time-honored methods as well as new practices brought on by changes in load, particularly machines, and in capacitors are covered. Although addressed to the machine-tool industry, the message applies equally to vendors of all types of electrical utilization equipment: other classes of production machinery and plant facilities. Emphasis is on the utilization system (usually 600 V or lower) where the benefits of capacity and efficiency are added to possible reduction in utility bills.