Drive Failure happens with High Harmonics


Drive Failure Industrial Drive Failure with power electronic-based AC VSD and DC Drive or computer hard disk drive, results in a power system with crammed harmonic energy sources. VSD and DC drives are NLL and harmonic generators. The solution is between costly derating or efficient harmonic solution as applied in this case study. In an industrial environment, the workstation's computer hard disk drive or data centre server's hard disk drive gets power through UPS. But UPS passes on momentary input voltage surge as dc ripple to its output and thus can't protect its loads from input voltage fluctuation. In-addition computer and servers loads at the UPS output generate zero-sequence harmonic which triples at neutral, causing high neutral current which tends to increase neutral voltage. Its effect fails the traditional protection devices like SPD and MOV. Encon facilitates the best solution in eliminating hard disk drive failure from voltage surge. An ACSR conductor manufacturing plant was facing high incidence of DC motor and AC VFD Drive Failure due to bad power quality and high harmonic distortion. The company is a world leader in non-ferrous metal industry. It manufactures ACSR conductors for HV and EHV power transmission and distribution lines. It had been facing a high incidence of operational problem across its plants A and B. It affected all electrical and electronic equipment with its conductor making process. In-addition, there were daily process interruptions due to nuisance tripping of DC/ VFD Drives. The problem arose because of two reasons. First, it was using over 60% Non-Linear-Loads in the forms of DC-drives in rolling mills, Variable-Frequency-Drives (VFD) in the conductor making process and PLC in control system. Second, it was operating at high load factor, in between 80 to 100%, of its transformer capacity. Load Factor is the actual running-load in mW/mVA divided by upstream transformer or diesel generator capacity in mW/mVA. World-wide most factories, buildings, and facilities, with similar nonlinear load profiles, run safely at around or even below 40% load factor. This is to keep most power qualities and harmonic problems under the carpet within its latent stage. Root cause of these are the rise in Total Harmonic Distortions, both THDv (voltage), and THDi (current), whose magnitudes are directly proportional to the plant's operating load factor; and that explains why de-rating helps in skirting the problem albeit with a guzzling infrastructure. The company was at the top of competition chain among peers. Fortunately, there exists an alternative that can effectively bring down harmonic distortions, both THDv and THDi, and improve the quality of power within an electrical power system. This is the domain and usefulness of Tuned Harmonic Filter that when designed appropriately reap rewards one can count on. It reconstructs the distorted waveform back into sine waves, thereby debottlenecks equipment capacity limitations, and removes barriers to energy efficiency from the plant and machineries; and transforms them instantly into impossible is nothing like performances, snippets of which are presented here. We installed four sets variable tuned harmonic filters, 500A, 1000A, 2000A and 4000A for 750kva, 1500kva, 2000kva and 3150kva transformers respectively. Each transformer was backed up by an appropriate sized back up DG. Each harmonic filter was designed to cover full load of its transformer, and backup DG, and were installed at the 415v main incoming LV PCC of each transformer, and its back up DG. The harmonic filters were designed for operating either with the grid/transformer source or the backup DG source, and the changeover between the grid-to-DG and DG-to-grid as well as adjustment in the plant's load variations, were accomplished automatically within the harmonic filter panel logics.

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