Miller Magazine Issue: 119 November 2019

57 COVER STORY MILLER / NOVEMBER 2019 to the largest motors, or in a bank in the Control Station. These capacitors are “power factor correctors”. The power factor is this coefficient: Power Factor = (True Power) (Apparent Power) If you correct the power factor to keep it over 90%, the electric company will reward you with a bonus in the bill. The usual arrangement is correcting the large motors with a fixed capacitor in their power line, and also a set of variable capacitors in the facility Power and Control Room to correct the rest of the power. SIMULTANEITY Plan your system so the largest motors don’t work all at the same time. For example, you could have a large bin near the mill to stock the grain you process through the day. This bin is filled through a path of elevators and belts of 1000 ton/hour. On the other side of the facility, you have the reception of the incoming grain, with its own set of conveyors and also cleaners and dryers. Why not scheduling the work so you fill the “daily bin” at night and only receive grain during the day? Not only you would use smaller components to con- trol the electric power, you also benefit of the lower costs of the electricity out of peak hours and stay in cheaper ranges of the bill. TAKE ADVANTAGE OF THE DAILY SCHEDULE Use electricity at the hours it is cheaper. Peak electricity use is at the hours everybody is home watching TV and having dinner, from 18:00 to 22:00, and at these hours it is the most expen- sive. Many electrical companies use a smart billing system that fluctuates the fee according to the hour of use. Scheduling the power intensive operations for the late night or the early morn- ing makes a lot of sense. TRY TO STAY AWAY OF PNEUMATICS Pneumatic conveying uses too much power. Yes, it is the most flexible solution for flour conveying, but it is also a power hog. In some operations you won’t be able to avoid it, because a mechanical solution would be too complex, but (as much as possible) try to use mechanical conveyors and gravity. That is the reason why most mills (of any grain) use a vertical layout, letting the grain fall from one stage of the process to another. KEEP YOUR WIRING IN GOOD CONDITIONS Too much energy is wasted through earth leakage currents. Ask your electrician to conduct a test with an Ohmmeter. If the test says there are any ground currents, check your entire installation. Wiring insulation could have been lost or damaged. I, myself, have been guilty of using standard wiring in places exposed to rain, causing ground currents after the insulation got soaked. Or rodents may have eaten the insulation away. There are as many safety reasons as economic reasons for keeping your electrical Average Full Load Nominal Efficiencies Standard and Energy Efficient Motors Rated hp Standard Motor* High-Efficiency Motor* 1.0 75.5 82.6 1.5 78.1 83.3 2.0 80.5 83.8 3.0 81.2 87.7 5.0 82.8 88.6 7.5 83.8 89.8 10.0 85.2 90.1 15.0 86.8 91.3 20.0 87.8 91.9 25.0 88.3 92.8 30.0 89.1 92.7 40.0 89.6 93.3 50.0 90.5 93.8 60.0 90.6 94.1 75.0 91.2 94.4 100.0 91.8 94.7 125.0 92.4 95.3 150.0 92.9 95.5 200.0 94.0 95.4 *Design B, Four Pole, Three-Phase