Modern Mining May 2021

or 2% saving on each adds up to a lot of savings. So, by all means, you may save power on a conveyor by greasing the rollers, but once you install an energy- efficient motor, you already have a definite efficiency benefit.” IE4 By 2020, South Africa was still importing and install- ing three times as many IE1 motors as their IE3 equivalent because of the difference in capital out- lay. Although Zest WEG is unaware of mining groups who still use IE1-compliant motors, Van Niekerk says smaller start-up operations with limited engineering capacity tend to purchase IE1 motors as the capex is “a few thousand rand lower”.

according to efficiency as either efficiency class IES0, IES1 or IES2. While Van Niekerk describes IEC 61800 as “a good standard” providing a benchmark for VSD manufacturers, he says it is not practical for use by end-users as it does not use the terminology familiar to industry. He says reputable companies who sell motors and drives will test the efficiency of the combination to IEC61800, but that many engineering firms are unaware of the IES rating for motor-drive combina- tions due to the confusing nature of this standard. “Another reason why users place little emphasis on IES ratings is that mechanical components within the system seldom have efficiencies above 80% whereas the typical motor will have an efficiency of some 95%. This brings the total difference in effi- ciency between an IE1 and an IE4 motor to only 2 or 3%, so why should the user bother with 2% sav- ings when the load is 80% efficient?” That thought, however, distracts the user from the real impact of such efficiency gains. He says it is not practical for mines or factories to constantly iron out these mechanical inefficien- cies in systems such as conveyor lines. Though the efficiency gains with motors or motor/drive combinations is lower than the potential mechanical gains, the advantage is that it is uncomplicated and certain, basically “install and save”. “As electrical power becomes more expensive in South Africa, it will become worthwhile to give enough attention to energy-efficiency gains and smarter maintenance practices. However, some end- users have as many as 50 000 motors installed. A 1

A WEG VSD is a means to improve the efficiencies of entire electrical systems.

The WEG IE4 super-premium efficiency motor.

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May 2021  MODERN MINING  35