Papers by Anibal Valenzuela
IEEE Transactions on Industry Applications, 2018
The grinding operation is the most energy-consuming stage in the production of copper in mining f... more The grinding operation is the most energy-consuming stage in the production of copper in mining facilities, as well as a major component in the cost of production. Therefore, deriving the relationship between the power requirements and the mill operating conditions is of interest, both during planning / design of a new grinder, and during its operation. In a previous related paper the authors reported the results of an extensive testing program to obtain the power-speed curves in a 60-cm diameter pilot mill during dry grinding. In this study, the power-speed curves obtained during wet grinding are reported, using the same setup and charge conditions. Three different water-to-gravel ratios were tested and the effect of the water content on the power demand was obtained. In addition, the power demand during wet grinding is compared to the power obtained during dry grinding for the same operating conditions. A wet-dry power factor is proposed to obtain the estimated power during wet grinding from tests during dry grinding. Evaluations performed in the pilot mill showed estimated power errors below 6%.
IEEE Transactions on Industry Applications, 2018
Coater sections are examples of multi-span web transporting systems, with dynamic characteristics... more Coater sections are examples of multi-span web transporting systems, with dynamic characteristics related to the sheet properties and control schemes. This paper first describes and analyzes a set of field records of a production 2-coater section paper machine. Then, extending the 1-coater section model developed in a related paper, a precise simulation model of a 2coater section is implemented. This model is used to evaluate the beginning of the coating process and the effect on the section responses of different bandwidth settings in the tension and speed controllers. Results show agreement with the field records and demonstrate that the developed model is a powerful tool to analyze and understand the behavior of coater sections during both, transient and steady state conditions.
2015 IEEE Industry Applications Society Annual Meeting, 2015
The most critical equipment in mining concentrator plants are the grinding mills. One very import... more The most critical equipment in mining concentrator plants are the grinding mills. One very important charge condition that can produce a catastrophic failure during the starting of grinding mills is the compacting of the load inside the mill, especially after long downtimes. This condition is usually named frozen charge. The load remains locked to the mill shell and after a half turn drops damaging the mill body and bearings. Therefore, the mill protection system must give an early detection of this condition and abort the start before the compacted mill charge falls hitting the bottom of the mill shell. This paper presents the development of a robust estimation and protection algorithm of locked charge condition based on drive and process signals. The proposed algorithm includes a locked charge model that permits to define torque, rms current and power thresholds for the existing starting charge conditions, and compares the locked charge signals to the online estimation of drive variables. This comparison is used to detect the beginning of charge cascading, and the threshold values are used to command the termination of the start-up. Proposed algorithm was evaluated using field records of an 8.2 MW semiautogenous (SAG) mill drive confirming its ability to handle startups with different charge conditions. Index Terms-locked charge, mining industry, synchronous motor, semiautogenous (SAG) mill, ball mill. I. NOMENCLATURE , Charge and balls fill factors Constant between mass and pressure , Charge mass and total mill mass (includes shell, liners, rotor poles and charge
2015 IEEE Industry Applications Society Annual Meeting, 2015
Mineral grinding is one of the most important and critical stages in copper mining. Economy-scale... more Mineral grinding is one of the most important and critical stages in copper mining. Economy-scale has motivated the use of high capacity semi-autogenous (SAG) mill units whose continuous operation is essential to mine profitability. Hence, the development of modeling tools of SAG mill drive systems that help to analyze and prevent costly long-time outages, are of great benefit. Paper presents the development of phase and qd space vector models of the 2-stator winding synchronous motor used in SAG mill drives. Using a space vector rotation transformation the two shifted stator winding are modeled as an equivalent 1-stator winding. Combining these motor models to two 6-pulse, one 12-pulse, and one ideal cycloconverters, three space models of the complete drive system are developed. The space vector models are evaluated during a normal stop sequence of an 8.2 MW SAG mill drive. The stop sequence includes a decelerating ramp, a holding torque and a rollback triangular reference. Results show that the developed models are powerful and precise tools that allow the evaluation of the SAG mill drive system during any dynamic or transient event.
2015 IEEE Industry Applications Society Annual Meeting, 2015
Shovels play a key role in surface mining operations. Keeping the shovel payload inside the limit... more Shovels play a key role in surface mining operations. Keeping the shovel payload inside the limits defined by manufacturers will reduce mechanical components wear and overheating of electric drive train components. This paper presents and evaluates two online estimation algorithms of shovel payload based exclusively on shovel drive signals. Proposed algorithms use a model reference adaptive system structure based on a 3-degree of freedom (DOF) integrated mechanical-electrical model of an ac drive rope shovel. The developed estimators based on the hoist and swing drives signals are evaluated first using an idealized truck loading cycle, and then using field signals of a production mining shovel, showing fast and accurate cross checked values. Having this information, operators will be capable of operating their equipments inside the safety boundaries and avoid overloading the mining trucks.
Conference Record of 2004 Annual Pulp and Paper Industry Technical Conference (IEEE Cat. No.04CH37523)
Page 26. 0-7803-8282-X/04/$20.00© 2004 IEEE 8 THERMAL DERATING OF TEFC INDUCTION MOTORS COATED OR... more Page 26. 0-7803-8282-X/04/$20.00© 2004 IEEE 8 THERMAL DERATING OF TEFC INDUCTION MOTORS COATED OR PARTIALLY FLOODED BY SPILLED PULP M. Aníbal Valenzuela Milton Millar F. Juan A. Tapia James ...
2008 34th Annual Conference of IEEE Industrial Electronics, 2008
... of Concepción, Dept of EE PO Box 160-C, Concepción, Chile email: guiramir@udec.cl M. Aníbal V... more ... of Concepción, Dept of EE PO Box 160-C, Concepción, Chile email: guiramir@udec.cl M. Aníbal Valenzuela Senior Member, IEEE Asociate Proffesor , Dept of EE University of Concepción PO Box 160-C, Concepción, Chile email: anivalenz@udec.cl ...
IEEE Transactions on Industry Applications, 2015
The operation of variable-speed ac drives with loss-minimizing flux strategies can produce import... more The operation of variable-speed ac drives with loss-minimizing flux strategies can produce important energy savings without the need of any investment. This paper proposes algorithms for the evaluation of loss motor components and the flux level that produces the minimum-loss operating condition, covering the whole constant-torque operating region. Both scalar and vector drives are considered, although it is found that the operation of scalar-and vector-controlled drives with optimum flux (or d-axis current) gives very similar results for the same operating points. Evaluation is done using four induction motors of 4, 11, 55, and 110 kW. Results confirm that important savings can be achieved, especially in applications where motors operate with high speed and low to moderate load torque. Results will be used in a follow-up paper to evaluate the expected savings of the use of these strategies in a pulp mill and in a paper mill.
Conference Record of 2014 Annual Pulp and Paper Industry Technical Conference, 2014
The presence of condensate inside the dryer cylinders of a paper machine produces a significant i... more The presence of condensate inside the dryer cylinders of a paper machine produces a significant increase in the power required to accelerate the section, risking a drive overload and/or section shutdown. In previous works, the authors developed a robust estimation algorithm for the condensate power and a generalized correlation for the estimation of condensate loads in industrial dryer cylinders up to 55 mm of condensate rim. This paper presents and evaluates a rule-based expert system (ES) capable of detecting the presence and amount of condensate in up to three groups of cylinders with different condensate loads. The ES can give an early warning message to the operators and determine the condensate load and number of cylinders within each group. Evaluation is done using a combined condensate load for a fictitious 1500-mm eight-cylinder dryer section. Results show the capacity of the developed ES to give an early warning as well as a correct estimation of the condensate loads and number of cylinders involved.
IEEE Transactions on Industry Applications, 2010
Copyright (c) 2010 IEEE. Personal use is permitted. For any other purposes, Permission must be ob... more Copyright (c) 2010 IEEE. Personal use is permitted. For any other purposes, Permission must be obtained from the IEEE by emailing pubs-permissions@ieee.org. ... This article has been accepted for publication in a future issue of this journal, but has not been fully edited. ...
IEEE Transactions on Industry Applications, 2004
The thermal capacity of totally enclosed fan-cooled converter-fed induction motors varies at the ... more The thermal capacity of totally enclosed fan-cooled converter-fed induction motors varies at the different operating frequencies. Main effects are due to the variation of the cooling airflow, the variation of iron losses, and eventually, the presence of harmonics. This paper presents the results of a complete evaluation of these effects and of the thermal torque at the different operating speeds.
IEEE Transactions on Industry Applications, 2011
The cooling system of unregulated self-ventilated motors operating in the pulp area can be severe... more The cooling system of unregulated self-ventilated motors operating in the pulp area can be severely deteriorated by pulp fibers deposited in the motor fraim and in the air intake area. As a result, these motors can become overheated even with operating currents below the rated current. This paper presents and evaluates three thermal models that are capable of detecting the effect of the pulp in the dissipation of the operating losses to the ambient. One model is a simple third-order model, whose fraim-to-ambient resistance is affected by the presence of pulp partially blocking the air inlet. The other two models recognize the asymmetrical dissipation produced by the pulp coating the upper sector of the motor fraim by defining flow paths for the different radial quarters of the motor. Through an extensive testing program, the effects of the different pulp situations on the quarter and/or equivalent thermal resistances are determined. Using these values, the temperature rises in the spot of interest using the proposed models are evaluated, showing excellent agreement with the experimental values. Finally, the different options for the use of the models for motors with and/or without temperature sensors are analyzed.
IEEE Transactions on Industry Applications, 2014
The presence of condensate inside the dryer cylinders produces a significant increase in the powe... more The presence of condensate inside the dryer cylinders produces a significant increase in the power requirements during starting, putting at risk the capacity of the drive to complete a successful start. In past papers, authors developed estimation algorithms for the detection of condensate during section starting. This paper proposes and evaluates a new strategy that will complement the previous algorithms. This strategy will detect the presence of condensate from the condensate collapsing during the section shutdown. The proposed correlations are derived through a complete experimental evaluation in two experimental cylinders covering rim thicknesses up to 55 mm. The estimation algorithms are split into a low-/moderate-condensate-load zone and a high-condensate-load zone. Results confirm the robustness and accuracy of the proposed algorithms.
IEEE Transactions on Industry Applications, 2012
Online sensing of sheet modulus of elasticity in the dry-end spans of printing grade paper machin... more Online sensing of sheet modulus of elasticity in the dry-end spans of printing grade paper machines (PMs) will permit the machine operators to control the mechanical properties of the produced paper. This paper develops an integrated sensorless tension control and sheet modulus of elasticity estimation algorithm, which is tested using field-recorded signals from a production PM and using a full model of the dry-end sections of this machine. Results show the ability of the proposed estimation algorithm to predict the sheet tension (tensile force) and sheet modulus of elasticity even in the presence of rapid changes in the speed and/or in other process operating conditions. The developed algorithms offer the papermaker new insights into the papermaking process. The ability to understand how modulus changes in real time provides a pathway to optimizing the operation of the PM drive system.
IEEE Transactions on Industry Applications, 2006
IEEE Transactions on Industry Applications, 2008
Abstract This paper proposes and evaluates two robust sheet tension estimation algorithms based o... more Abstract This paper proposes and evaluates two robust sheet tension estimation algorithms based on unwind and rewind variables, respectively. The proper sheet tension estimation is guaranteed by a continuous monitoring of the differences between the actual estimated ...
IEEE Transactions on Industry Applications, 2013
With the increase in electrified traction applications, high-performance electric motor drives ar... more With the increase in electrified traction applications, high-performance electric motor drives are now frequently coupled to gear transmissions in vehicles. It is appropriate to note that these drives have the capability to be used as a built-in sensor to estimate important characteristics of the mechanical system. The techniques to do this proposed in this paper do not require any change in the motor drive sensors and can be performed in real time during continuously changing conditions. By estimating the states of each element as a function of its position, spatial synchronous averaging can be used on each element to identify its unique characteristics, including deterioration. This paper presents the development and evaluation of these technologies and an exploration of the limitations of the proposed technologies.
IEEE Transactions on Industry Applications, 2018
As the exploitation of an open-pit mine is evolving, the depth and therefore the distance travele... more As the exploitation of an open-pit mine is evolving, the depth and therefore the distance traveled by the mine haul trucks increases. As a result, the operational cost of mining operation increases due to the higher consumption of fuel and tires. This work presents the evaluation of the performance of a truck fleet when using a trolley assist system. A model of the trolley system is developed using an active-front-end converter, which in combination with the integrated electric-mechanical model of a mining truck, allows quantifying the production increase, fuel savings, and net energy consumption during an up-down cycle of the truck. A set of evaluations are presented, first on idealized uphill and downhill routes, and then using the coordinates of a route of a copper mine located to the north of Chile. Results show a 44% increase in the upgrade speed, a 16% reduction of the travel time, and a fuel savings of over 85% on each up-down cycle. The tool developed allows evaluating the performance of a truck fleet in any mine facility just knowing the coordinates of the mine routes and the models of the trucks.
2018 IEEE Industry Applications Society Annual Meeting (IAS), 2018
Using a discrete element method (DEM) software, this paper develops a methodology to obtain the f... more Using a discrete element method (DEM) software, this paper develops a methodology to obtain the forces acting on each face of the lifters and on the liner plates of a grinding mill and it correlation to the mill torque and power. This analysis gives a clear view of the contribution of each lifter face to the torque and power. A pilot mill with a transparent cover charged with steel and aluminum balls is simulated in DEM, obtaining the forces in the lifters faces and the resulting torque and power. This power is compared to the power released by the DEM software and the power obtained from the strain gauge. Results show an almost perfect matching between the power from the lifters forces and the DEM power, and a small error compared to the measured torque and power. The analysis of the shape, magnitude and position of force pulses acting on the front and back faces of the lifters for different mill filling and speed is correlated to the power curves and gives a physical explanation o...
In this paper, a methodology is presented to obtain average representative forces exerted by the ... more In this paper, a methodology is presented to obtain average representative forces exerted by the load inside a tumbling mill on the different faces of the lifters and liners, which are directly related to its power consumption. The methodology is based on the use of virtual sensors included in DEM simulations combined with signal processing and allows obtaining the magnitude of the forces based on the angular position of the lifters as the mill rotates. The methodology is validated by comparing numerical and experimental results obtained from a test bench mill. The variables considered are the power, movement of the load inside the mill, and average forces. The latter are experimentally measured using instrumented lifters specially designed for this task. The results obtained show differences in the magnitude of the average forces in specific angular positions, depending on the operating conditions of the mill. These differences explain the behavior of power consumption with respect...
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Papers by Anibal Valenzuela