Considerations about Maximum Temperature of Toroidal Transformers in Steady-State Conditions

2020 ◽  
Vol 7 (1) ◽  
pp. 22-29
Author(s):  
Adrian Pleșca ◽  
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Ambient Temperature ◽  
Electric Current ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Maximum Difference ◽  
Novel Method ◽  
Theoretical Results

In this paper, a novel method based on a thermal mathematical model which includes the main geometrical, physical and thermal parameters of the toroidal transformer has been developed in order to obtain the maximum temperature inside the transformer during steady-state operating conditions. The influence of electric current and ambient temperature on the maximum temperature has been investigated. To validate the proposed method, some experimental tests have been done. The analyzed transformer had a rated power of 2kVA and the rated primary voltage of 230V. There is a good correlation between experimental and theoretical results with a maximum difference of 3°C.

scholarly journals Comprehensive Parameters Identification and Dynamic Model Validation of Interior-Mount Line-Start Permanent Magnet Synchronous Motors

Machines ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 4 ◽  
Author(s):  
Luqman S. Maraaba ◽  
Zakariya M. Al-Hamouz ◽  
Abdulaziz S. Milhem ◽  
Ssennoga Twaha
Keyword(s):  
Mathematical Model ◽  
Permanent Magnet ◽  
High Efficiency ◽  
Experimental Tests ◽  
Induction Machines ◽  
Test Methods ◽  
Operating Conditions ◽  
Test Method ◽  
Permanent Magnet Synchronous Motors ◽  
Synchronous Motors

The application of line-start permanent magnet synchronous motors (LSPMSMs) is rapidly spreading due to their advantages of high efficiency, high operational power factor, being self-starting, rendering them as highly needed in many applications in recent years. Although there have been standard methods for the identification of parameters of synchronous and induction machines, most of them do not apply to LSPMSMs. This paper presents a study and analysis of different parameter identification methods for interior mount LSPMSM. Experimental tests have been performed in the laboratory on a 1-hp interior mount LSPMSM. The measurements have been validated by investigating the performance of the machine under different operating conditions using a developed qd0 mathematical model and an experimental setup. The dynamic and steady-state performance analyses have been performed using the determined parameters. It is found that the experimental results are close to the mathematical model results, confirming the accuracy of the studied test methods. Therefore, the output of this study will help in selecting the proper test method for LSPMSM.

Transient Thermoelastohydrodynamic Study of Tilting-Pad Journal Bearings Under Dynamic Loading

1998 ◽  
Vol 120 (2) ◽  
pp. 405-409 ◽  
Author(s):  
P. Monmousseau ◽  
M. Fillon ◽  
J. Freˆne
Keyword(s):  
Steady State ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Tilting Pad ◽  
Transient Period ◽  
Final Steady State ◽  
Tilting Pad Journal Bearings

Nowadays, tilting-pad journal bearings are submitted to more and more severe operating conditions. The aim of this work is to study the thermal and mechanical behavior of the bearing during the transient period from an initial steady state to a final steady state (periodic). In order to study the behavior of this kind of bearing under dynamic loading (Fdyn) due to a blade loss, a nonlinear analysis, including local thermal effects, realistic boundary conditions, and bearing solid deformations (TEHD analysis) is realized. After a comparison between theoretical results obtained with four models (ISO, ADI, THD, and TEHD) and experimental data under steady-state operating conditions (static load Ws), the evolution of the main characteristics for three different cases of the dynamic load (Fdyn/Ws < 1, Fdyn/Ws = 1 and Fdyn//Ws > 1) is discussed. The influence of the transient period on the minimum film thickness, the maximum pressure, the maximum temperature, and the shaft orbit is presented. The final steady state is obtained a long time after the appearance of a dynamic load.

Thermal Simulation Benchmark of Graphic Module Under Installed, Operating Conditions

2005 ◽  
Author(s):  
Fariborz Forghan ◽  
Gregory J. Kowalski ◽  
Mansour Zenouzi ◽  
Hameed Metghalchi
Keyword(s):  
Steady State ◽  
Computer Games ◽  
Electronic Device ◽  
Thermal Response ◽  
Thermal Simulation ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Software Environment ◽  
Transient Thermal ◽  
Graphic Module

The thermal performance of a graphic module on graphic card is theoretically and experimentally investigated. Unlike prior benchmark studies, this study involves a practical electronic device operating in a real software environment. The temperatures at five locations on the module and at one point on the board are measured as a function of time during the operation of a series of computer games. The theoretical model is developed using Flotherm to simulate the transient thermal response. There is close agreement from 3% to 10% between the numerical steady state case prediction and test data. The calculated transient trends using Flotherm model closely agree with experimental results and demonstrate the rapid increase in temperature as the number of module operations increases during the games. The results for the maximum temperature are directly linked to the software operation and exhibit a superposition type behavior in which the observed maximum operating temperature can exceed that estimated by steady state conditions. As expected, the results demonstrate that a carefully constructed thermal simulation can accurately predict the thermal response of a module under actual operating conditions.

A new model to predict the behaviour of cavitated squeeze-film bearings

1987 ◽  
Vol 411 (1841) ◽  
pp. 445-466
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Lift Force ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Successful Operation ◽  
New Model ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Linear Damping

Squeeze-film bearings are used extensively to control vibration in rotor-bearing systems. No closed-form mathematical model exists to represent the stiffness and dam ping characteristics of a cavitated squeeze-film bearing when it is describing a non-circular, non-concentric orbit. In this paper nonlinear expressions are developed for the oil-film forces from which are derived two direct linear stiffness and two direct linear damping coefficients with all the cross stiffness and dam ping coefficients zero. The linearized stiffness coefficients and the damping coefficients are functions of the amplitude of the journal orbit. The dynamic lift-force which is fundamental to the successful operation of a cavitated squeeze-film bearing when designed without centralizing springs has not previously been predicted analytically. An expression is derived for this lift force. Its magnitude is shown to be dependent upon the amplitude of the steady-state orbit, that is, it is dependent upon the dynamic load. A numerical experiment is performed to assess the validity of the new model over a range of operating conditions.

CFD Simulation of the CANDU-6 Moderator Circulation Under Normal Operating Conditions

2002 ◽  
Author(s):  
Bo Wook Rhee ◽  
Churl Yoon ◽  
Byung-Joo Min
Keyword(s):  
Steady State ◽  
Cfd Simulation ◽  
Volumetric Flow Rate ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Outlet Temperature ◽  
Frictional Pressure Drop ◽  
The Core ◽  
Hydraulic Impedance ◽  
Center Region

A steady-state 3D simulation for predicting the local subcooling of the moderator in the vicinity of the calandria tubes in a CANDU-6 reactor is performed. For the current simulation, a set of grid structures with the same geometry as the CANDU-6 moderator tank, called ‘calandria vessel’, is generated and the momentum, heat and continuity equations are solved by CFX-4.3, a CFD code developed by AEA technology. The standard k-ε turbulence model associated with logarithmic wall treatment is used to model turbulence generation and dissipation within the vessel. The moderator fluid is heavy water. Buoyancy forces are modeled using the Boussinesq approximation in which density is assumed to be a linear function of temperature. The matrix of the calandria tubes in the center region of the calandria vessel is simplified by the porous media approach. The anisotropic hydraulic impedance of the calandria tubes is modeled using the frictional pressure drop correlations suggested by Idelchik and Szymanski. The heat load in this steady-state simulation is conservatively set as 103 MW of 103% full power, consisting of 96.7 MW to the core region and 6.3 MW to the reflector region. The total volumetric flow rate through eight inlet nozzles is 940 L/s and the outlet temperature is constantly 71.0 °C. The thermal boundary condition of the circumferential vessel wall is assumed a little heat flux out. As a result, the velocity field and temperature distribution of a CANDU-6 moderator in the operating condition are presented. The flow pattern identified in this simulation is the weak jet momentum-dominated flow, which is generated by the interaction between the buoyancy force by heating and the dominant momentum forces by inlet jets. The calculated maximum temperature of the moderator is 83.0 °C at the lower center region of the core, which corresponds to the minimum subcooling of 33.0 °C considering the boiling point increase due to the hydrostatic pressure change.

scholarly journals Influence of Interfacial Traps on the Operating Temperature of Perovskite Solar Cells

2019 ◽  
Author(s):  
Hooman Mehdizadeh-Rad ◽  
Jai Singh
Keyword(s):  
Mathematical Model ◽  
Solar Cells ◽  
Ambient Temperature ◽  
Phase Change ◽  
Active Layer ◽  
Heat Generation ◽  
Operating Temperature ◽  
Perovskite Solar Cells ◽  
Operating Conditions ◽  
Interface Passivation

In this paper, by developing a mathematical model, the operating temperature of perovskite solar cells (PSCs) under different operating conditions has been calculated. It is found that by reducing the density of tail states at the interfaces, acting as recombination centres, through some passivation mechanisms, the operating temperature can be reduced significantly at higher applied voltages. The results show that if the density of tail states at the interfaces is reduced by three orders of magnitude through some passivation mechanisms, then the active layer may not undergo any phase change up to an ambient temperature 300 K and it may not degrade up to 320 K. The calculated heat generation at the interfaces at different applied voltages with and without passivation shows that the heat generation can be reduced by passivating the interfaces. It is expected that this study may provide a deeper understanding of the influence of interface passivation on the operating temperature of PSCs.

scholarly journals INFLUENCE OF THERMAL RESISTANCE OF AIR CONDENSER TUBES ON STEAM COOLING EFFICIENCY

2020 ◽  
Author(s):  
J. Jianguo ◽  
G. Varlamov ◽  
K. Romanova ◽  
L. Suxiang ◽  
L. Zhigang
Keyword(s):  
Mathematical Model ◽  
Thermal Resistance ◽  
Ambient Temperature ◽  
Cooling System ◽  
Steam Pressure ◽  
Operating Conditions ◽  
Air Cooling ◽  
Cooling Unit ◽  
Air Condenser ◽  
Working Bodies

The research is carried out using a mathematical model of conditions and features of condensation processes with the influence of changes in internal and external thermal resistances of working bodies, which occur during contamination of outside and inside metal pipes of heat exchange surfaces of air condenser. capacitor. Particular attention is paid to the selection, detailing and determination of more than twenty basic parameters that characterize the operation of the direct cooling unit of the condensing unit for the summer, the conditions of heat transfer processes between the working bodies taking into account the finned outer surface of elliptical condenser tubes. The results of experiments on the mathematical model are analyzed and the influence of the incoming air velocity and ambient temperature on the output steam pressure in the condenser direct air cooling system within the change of internal and external thermal resistances in the range 0-0.001(m2·K)/W due to cooling tube contamination is determined. air condenser steam turbine installation. Conditions, character and features of influence of thermal resistance of pollution in cooling tubes on steam pressure at an exit from them are defined, the basic factors defining steam pressure at an exit, necessity of the organization of control of thermal resistance of pollution in a pipe during unit operation at variable operating conditions and expediency is substantiated. conducting test studies of operating modes while taking into account the influence of thermal resistance of external and internal pollution on the thermal efficiency of the cooling unit. Studies have shown that at a fixed value of the heat load of the exhaust steam, the pressure of the steam outlet increases with increasing ambient temperature and decreasing the speed of the incoming air.

scholarly journals Thermal Analysis of Power Semiconductor Device in Steady-State Conditions

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 103 ◽  
Author(s):  
Adrian Plesca
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Semiconductor Device ◽  
Experimental Tests ◽  
Junction Temperature ◽  
Inductive Load ◽  
Power Semiconductors ◽  
Power Semiconductor ◽  
Air Speed ◽  
Good Concordance

Electronic devices can be damaged in an undesirable manner if the junction temperature achieves high values in order to cause thermal runaway and melting. This paper describes the mathematical model to calculate the power losses in power semiconductor devices used in bidirectional rectifier which supplies a resistive-inductive load. The obtained thermal model can be used to analyse the thermal behaviour of power semiconductors in steady-state conditions, at different values of the firing angle, direct current, air speed in the case of forced cooling, and different types of load. Also, the junction and case temperature of a power thyristor have been computed. In order to validate the proposed mathematical model, some experimental tests have been performed. The theoretical values are in good concordance with the experimental data and simulated results.

Transient Thermoelastohydrodynamic Study of Tilting-Pad Journal Bearings Under Dynamic Loading

1997 ◽  
Author(s):  
Pascal Monmousseau ◽  
Michel Fillon ◽  
Jean Frêne
Keyword(s):  
Steady State ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Tilting Pad ◽  
Transient Period ◽  
Final Steady State ◽  
Tilting Pad Journal Bearings

Nowadays, the tilting-pad journal bearings are submitted to more and more severe operating conditions. The aim of this work is to study the thermal and mechanical behavior of the bearing during the transient period from an initial steady-state to a final steady-state (periodic). In order to study the behavior of this kind of bearing under dynamic loading (Fdyn) due to a blade loss, a nonlinear analysis, including local thermal effects, realistic boundary conditions and bearing solid deformations (TEHD analysis) is realized. After a comparison between theoretical results obtained with four models (ISO, ADI, THD and TEHD) and experimental data under steady-state operating conditions (static load Ws), the evolution of the main characteristics for three different cases of the dynamic load (Fdyn/Ws<1, Fdyn/Ws=1 and Fdyn/Ws>1) is discussed. The influence of the transient period on the minimum film thickness, the maximum pressure, the maximum temperature and the shaft orbit is presented. The final steady-state is obtained a long time after the appearance of a dynamic load.

scholarly journals Bimetallic ammeter: a novel method of current measurement

2020 ◽  
Vol 4 ◽  
pp. 2
Author(s):  
Robert Frederik Uy ◽  
Qiaozi Miao ◽  
Chenghao Yuan
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Thermal Expansion ◽  
Specific Heat ◽  
Electric Current ◽  
Mechanical Displacement ◽  
Novel Method ◽  
Specific Heat Capacities ◽  
Experimental Values ◽  
Good Agreement

An electric current flowing through a bimetallic coil heats it up, and due to thermal expansion, the coil either unwinds or winds depending on the direction of net heat transfer and the specific heat capacities of the metals used. This means that by relating a certain measure of its mechanical displacement with current, the bimetallic coil can be used as an ammeter. Thus, a mathematical model relating the current to the time taken by the bimetallic coil to unwind a fixed displacement was developed and verified through experiments, which show a good agreement between theoretical and experimental values.

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