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1

A computationally low burden MPTC of induction machine without prediction loop and weighting factor

Kiani Babak

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 4

art. no. e142050

EN

This paper presents a novel method to overcome problems of finite set-model-based predictive torque control (MPTC) which has received a lot of attention in the last two decades. Tuning the weighting factor, evaluating a large number of switching states in the loop of the predictive control, and determining the duty cycle are three major challenges of the regular techniques. Torque and flux responses of deadbeat control have been developed to overcome these problems. In our method, firstly, the prediction stage is performed just once. Then, both the weighted cost function and its evaluation are replaced with only simple relationships. The relationships reduce torque ripple and THD of stator current compromisingly. In the next step, the length of the virtual vector is used to determine the duty cycle of the optimum voltage vector without any additional computations. The duty ratio does not focus on any relation or criteria minimizing torque or flux ripple. As a result, torque and flux ripples are reduced equally. The proposed duty cycle is calculated by using a predicted virtual voltage vector. Hence, no new computation is needed to determine the proposed duty cycle. Simulation and experimental results confirm both the steady and dynamic performance of the proposed method in all speed ranges.

2

Energy saving rates for a multistage centrifugal pump with variable speed drive

Rakibuzzaman M., Kim K., Kim H.-H., Suh S.-H.

Journal of Power Technologies

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2017

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Vol. 97, nr 2

163--168

EN

Multistage centrifugal pumps with variable speed drives are currently widely used in a variety of industrial and commercial applications. However, there are limitations to defining the efficiency of variable speed drive pumps. As an alternative method, energy saving rates can be evaluated with flow patterns and mean duty cycles. Computational fluid dynamics (CFD) is being used as a good tool to understand this and is less time consuming in terms of analyzing performances the experimental method. Research attention was focused on the energy saving rates of a multistage centrifugal pump for variable flow with variable speed drive through numerical and experiment methods. For this investigation Reynolds-averaged Navier-Stokes (RANS) equations were discretized by the finite volume method and a two equations SST model was used to account for three dimensional steady state flows. In the experimental system, an experimental set-up of a variable flow system was made to obtain energy saving rates and computational results were validated. The energy saving rates of the pumps depend on the flow patterns and specific mean duty cycles on which the machine or system operates. Mean duty cycles were divided into different flow operating conditions and a weighting for the mean value was given for each segment according to interval time. The pump system was operated at 50_70% of maximum flow rates. The energy saving rates were obtained from input power through CFD simulation and experimentally, and the mean duty cycle was obtained from flow patterns in the field of the pump. Energy saving rates were evaluated as a function of mean duty cycle and input power of the system operation. The total energy consumed for the constant speed drive was 25,922 kWh and for the variable speed drive pump was 17,687 kWh through CFD. The total annual energy saving rates were annually 33.81% through computational and 31.77% through experimental method with the variable speed drive system when compared to the constant speed drive system.

3

Elektroerozyjne drążenie otworów o małych średnicach w materiałach o dużej przewodności cieplnej

Sosinowski Ł.

Mechanik

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2015

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R. 88, nr 12CD1

10--14

PL

W artykule przedstawiono wyniki badań wpływu czasu impulsu ton, czasu przerwy tp oraz zmiany ciśnienia dielek-tryka p, przy ustalonych pozostałych parametrach obróbki EDM, na wybrane parametry struktury geometrycznej obrabianej powierzchni, zużycie elektrody roboczej Ze oraz czasu drążenia td.

EN

The paper presents the results of the influence of the pulse time ton, the interval time tp and pressure change of the dielectric p, at the fixed others parameters of Electrical Discharge Machining on selected parameters of the geometric structure of the treated surface, electrode wear Ze and drilling time td.