- Bauxite Mining Operation
Low power factor problems are a common occurance at facilities that operate heavy loads such as induction motors. Most often, plant managers discover the problem when the utility bill arrives with an unplesant surprise, costly power factor penalty or peak kVA demand billing catagory to compensate for the “total power” required by a customer. Other signs of power factor problems are motors running hotter than usual and transformers being overloaded.
“A low power factor means uncorrected heavy motor loads from indusction motors in heavy machinery or HVAC equipment” says Rich Zucarro, Power Factor Program Manager, Staco Energy Products Company. “Poor power factor can cause low voltage. When motors run at low voltage they require additional maintenance and are more likely to burn out.” Correcting power factor problems with capacitors is the answer, and is evidenced by the experience of a mining company that relies on large diesel generators for their on-site power generation the savings on fuel and maintenance make for and astonding return on investment.
In this case, the customer mines bauxite for aluminum, and operates two 1.6 MW, plus two MW diesel generators. Fuel expenditures can exceed $5 Million a year. Maintenance and engineering determined that they could experience savings with the addition of power factor correction capacitors, and launched the project. They were surprised when they did the calculations and how fast the payback could be realized.
The expected saving is $650,000 peryear from the project, and the expected payback is in less than a year. They have lots of generators that will be alternated when they need power and this will allow them to use the generators less per day, so the operating hours and operations will benefit. The plant;s power factor before the project was 74 percent, a relatively low power factor, according to Zucarro. A correction to 90 to 95 percent is typical to avaid utility penalties, where they chose to correct to 95%
“The interesting thing was they had asked us to look at a number of variable frequency drives and those drives generate harmonics” says Zucarro. “Capacitors don’t operate very well in a harmonic-rich environment due to the high frequency of the harmonics. However, we were able to apply several de-tuned capacitor banks which reduced the harmonic level at the capacitors to operate successfully and further increase fuel savings.”
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