Most of the applications used in underground mining industries (explosion-proof environment) are performing in heavy-duty load conditions. As a result, standard designs of explosion-proof, water-cooled squirrel cage induction motors (WC-SCIM) equipped with standard designs of die-cast aluminium rotors (DCAR) are exposed to higher than expected rotor bar current values. Site investigations and dynamometer tests confirmed that severe heavy-duty loading induce high thermo-mechanical stresses (TMS) in DCARs. Frequent occurrences of such TMS (superimposed on the rated condition stresses) may bring conductive material (Aluminum) of the rotor bars to its fatigue conditions initiating rotor degradation process with subsequent influence on motor performances with consequent financial losses. The paper uses multidisciplinary techniques to study the ageing process of Die Cast Aluminum in Squirrel Cage Rotors Exposed to Heavy-Duty Load Conditions of a 50 hp SCIM equipped with DCAR. Based on claims regarding performance degradations, the research started with site measurements confirming the adverse heavy-duty load conditions. Statistic-probabilistic methods are used to determine Reliability indicators by using Fault Tree Method (FTM). The mathematical model confirmed the motor reliability and enable detection of weak points of the motor. Thermodynamic calculations are used to assess motor performances and its reliability by estimating air gap reduction and heat transfer to the bearings as the two major consequential effects of the TMS developed within DCAR. Dynamometer tests have been used to replicate the site conditions enabling creation of a mathematical model of thermal stress inside the rotor bars. After specific dynamometer tests a number of rotors have been cut-open to investigate the intimate rotor bar degradation. While there are various methods of detecting failed rotor bars, a Secondary research performed by authors indicate that to date no other research has been undertaken in studying this phenomenon.
In actual economic environment, business sustainability requires high-efficiency technological processes. While Government and Utilities Demand Side Management (DSM) programs consider energy consumption (E Used ) as a whole, proposed method splits energy in 2 (two) specific components: Ideal energy (E Ideal ) and Energy at Risk (E@R). Considering these two types of energy a Benchmark Energy Factor (BEF) can be defined. BEF compares the energy used by industrial system or processes (IS&P), E used to the minimum energy required to accomplish the task at hand E ideal . Ideal energy (power) can be very accurate calculated by using adequate (well known) laws of physics chosen function of the work type performed by IS&P, therefore a solid (not empirical) reference for benchmarking system is available. That eliminates traditional variability that uses variable baselines as "best practice" or other criteria. Volatile comparative element across an industrial sector is replaced with a theoretical goal with a scientific set-up. BEF enables a new approach towards energy efficiency in industrial sector and help level the playing field for energy management. Proposed method promotes a sustainable and consistent approach making possible to determine accurately the (E@R) under variable material and environmental conditions making possible to manage the energy losses. The rating is then solely based on how close the true energy consumption within an IS&P gets to that ideal state. From economic standpoint, these sustainability concepts favor high-efficiency systems, as any energy-efficient system translates into higher effective productivity. Paper proposes a rating system model to describe the energy-efficiency for any IS&P independent of a comparison with others. BEF enables a reliable rating system model describing energetic efficiency of any IS&P that can be used by U.S. Department of Energy-Energy-Star Certification for Plants Program replacing existent benchmarking practice. Case study assessing IS&P by using (E@R) and (BEF) concepts with development of a new standard is presented.
While DSM programs consider energy consumption (E Used ) as a whole, proposed method splits energy in 2 (two) specific components: Ideal energy (E Ideal ) and Energy at Risk (E@R). Considering these two types of energy a Benchmark Energy Factor (BEF) can be defined. BEF compares the energy used by an industrial system or process, E used to the minimum energy required to accomplish the task at hand E ideal . Ideal energy (power) can be very accurate calculated by using adequate (well known) laws of physics chosen function of the work type performed by Drive End-use Equipment (DEE), therefore a solid (not empirical) baseline for benchmarking system will be available. That will eliminate traditional variability that uses variable baselines as "best practice" or other criteria. Volatile comparative element across an industrial sector will be replaced with a theoretical goal. BEF enables a new approach towards energy efficiency in industrial sector and help level the playing field for energy management. It will be demonstrated that (E@R) variation is embedded in (BEF). Proposed method makes possible to determine accurately the (E@R) under variable material andenvironmental conditions making possible to manage the energy losses. The rating is then solely based on how close the true energy consumption within an industrial process gets to that ideal state. Paper proposes a rating system model to describe the energy-efficiency for any industrial process independent of a comparison with other processes. Case studies assessing industrial conservation opportunities by using (E@R) and (BEF) concepts on various industrial sectors and processes (IS&P) are presented.
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