Improve process controllability by variable frequency drive

In certain processes a variable frequency drive is an essential part of the control system as without a means to start the process slowly, and slowly increase production rate, the process would be impossible to start or control. A typical example of this would be a paper machine where a slow start up is required and control of the speed of each stage of the machine depends on the previous stage and the required draw or stretch.

In the grinding mills used in minerals extraction from various ores, the addition of a variable frequency drive to control the mill speed provides an opportunity to compensate for variations in density, and other characteristics of the milled ore, by providing a further degree of freedom. This may lead to a decrease in specific energy consumption without sacrificing output product quality or daily production.

In the chemical production industry, the temperature control of various reagents has been kept in a much smaller temperature band by using variable frequency drive driven fans on the fin-fan coolers. Previously fans had to be stopped and started when the temperature deviated outside a given temperature band. As motors cannot be started and stopped more than a given number times per hour, the temperature band was a lot wider. The use of variable speed driven fans has led to a higher quality of output product as well as increased production efficiencies, resulting in a more profitable process.