Mohamad Kamarol Mohd Jamil

A Comprehensive Analytical Subdomain Model and Its Field Solutions for Surface-Mounted Permanent Magnet Machines

This paper presents a comprehensive analytical subdomain model together with its field solutions for predicting the magnetic field distributions in surface-mounted permanent magnet (PM) machines. The tooth tips and slotting effects during open-circuit, armature reaction, and on-load conditions are considered when deriving the model and developing its solutions. The model derivations and field solutions are extended from a previous model, and can be applied to PM machines with any combinations of slot and pole numbers and any magnetization patterns in the magnets. This model is initially formulated according to Laplaces and Poissons equations in 2-D polar coordinates by the separation of variables technique in four subdomains, such as magnet, airgap, winding slots, and slot-openings. The field solution of each subdomain is obtained applying the appropriate boundary conditions and interface conditions between every two subdomains, respectively, which can precisely account for the mutual influence between slots. Finite element analysis (FEA) is later deployed to validate the analytical results in a surface-mounted PM machine that has nonoverlapping winding arrangement. For validation purposes, PM machines having 3-slot/2-pole with parallel magnetization and 12-slot/10-pole with either parallel or radial magnetizations are used for comparisons. Computation of global quantities for the motor which include the phase back-EMF and cogging torque is also included. The results indicate that the proposed analytical model can accurately predict the magnetic field distributions in each subdomain and the motors global quantities, which are in good agreement with those obtained from the FEA.

Study on the electromagnetic force affected by short-circuit current in vertical and horizontal arrangement of busbar system

Each busbar conductor of a phase is subjected to a force due to the short-circuit currents. In this paper, the electromagnetic forces affected by the short-circuit current in three-phase busbar conductor are calculated in vertical and horizontal arrangement. The short-circuit current densities are calculated mathematically. The calculations are performed by assuming a peak value of steady-state ac current is equal to the peak value of the short-circuit current. The electromagnetic forces due to the short-circuit current are calculated according to the equation introduced by IEC Standards 865/1993. The electromagnetic force generated in vertical arrangement is compared with the horizontal of busbar. The result depicted that the busbar in vertical arrangement has about 2 times higher electromagnetic force compared with that in horizontal arrangement. The arrangement of the busbar obviously influences the strength of electromagnetic force due to short-circuit current. Furthermore, the electromagnetic force obtained from the simulation by finite element method in vertical arrangement was agree with the calculation obtained using IEC Standard 865/1993.

Investigation of electromagnetic force during short-circuit test in three-phase busbar system

All busbar systems are subjected to electromagnetic forces which may cause permanent mechanical deformation and damage if large electromagnetic force occurs due to short-circuit current. Therefore, the predictions of electromagnetic force on the three-phase busbar system is very important, especially to analyze it effect on the mechanical structure of busbar system. In this paper, two finite element models of busbar system having different rated currents are presented. Each model of busbar system has different mechanical dimensions. The electromagnetic forces generated in conducting busbars are analyzed under short-circuit conditions. The electromagnetic force is obtained using transient analysis by applying Maxwell Stress equation. Higher peak short-circuit current contributes to the generation of higher electromagnetic force between parallel conductors. The finite element models predict the busbars will experience peak short-circuit current of 63kA and 73.5kA, thus, generating about 62.5242 N/mm and 67.8617 N/mm of electromagnetic forces respectively, in between the conducting busbars. Optimal design for the mechanical dimensions and supporting structure for the three-phase busbar system can be intensively simulated taking into account the maximum electromagnetic force allowable. The results indicate that the magnitude electromagnetic force can be reduced by 4%–7% when the dimensions of conducting busbar thickness and its spacing are increased by 1mm. The results obtained are useful for the mechanical design and determination of supporting structure of the busbar system.

Complete subdomain model for surface-mounted permanent magnet machines

This paper presents a complete and improved analytical subdomain model for predicting the magnetic field distributions in surface-mounted permanent magnet (PM) machines accounting for tooth-tips and slotting effect, during open-circuit, armature reaction and on-load conditions. The model analytical derivations and field solutions are extended to overcome the shortcoming in previous subdomain model, and can be applied on PM machines having any combination of slots and pole numbers and any magnetization pattern in the magnets. This model is initially derived based on Laplaces and Poissons equations in polar coordinates by the separation of variables technique in four subdomains, i.e., magnet region, airgap, winding slots, and slot-openings. The field solutions in each subdomain are obtained by applying the appropriate boundary conditions and interface conditions. Finite element analysis (FEA) is later deployed to validate the analytical results in surface-mounted PM machine having a non-overlapping winding arrangement. The results show that the proposed analytical model can accurately predict the magnetic field distributions in each subdomain in PM machines.

Breakdown voltage characteristics of RBD Palm Olein and Envirotemp FR3 mixture under quasi-uniform electric field

This paper reported the experimental result of breakdown voltage characteristics of Refined, Bleach and Deodorized Palm Olein (RBDPOlein) with 10–50% of Envirotemp FR3 oil (FR3) mixture. The experiment was conducted at the temperature of room temperature (26°C–27°C), 40°C, 50°C, and 60°C under quasi-uniform electric field of AC applied voltage. Experimental result revealed the increases trend of breakdown voltage with the increasing of FR3 ratio. All the breakdown voltage of RBDPOlein and FR3 mixture is fulfill the IEC 60156 standard which is greater than 30kV. The result of chemical compositions of the oil mixture was also investigated. The fatty acid composition of the oil mixture shows the decrement of palmitic acid, and oleic acid with significant increment of linoleic acid and linolenic acid. The chemical composition test also reveals the presents of antioxidant additive, BHT in FR3, which might be give an effect to the increment of insulation strength.

Effect of Calcination Temperature on the Breakdown Strength and Energy Density of CaCu 3 Ti 4 O 12 Ceramic

The effect of calcination temperature on the breakdown strength and energy density of CaCu3Ti4O12 (CCTO) ceramics was studied. CCTO ceramics were prepared via solid state reaction method. The raw materials of CCTO were wet mixed for 24 hours and then dried overnight in oven. CCTO mixtures were calcined at three different temperature which is at 900°C, 930°C and 950°C for 12 hours. The calcined powders were compacted at 250 MPa and then were sintered at 1040°C for 10 hours. X-Ray Diffractometer (XRD) analysis showed the formation of CCTO phase and secondary phases of CuO and CaTiO3 for C900 calcined powders but single phase of CCTO was obtained by C930 and C950 calcined powders. Single phase of CCTO also were seen for all sintered samples. Observation on Scanning Electron Microscopy (SEM) micrographs showed large grain size was seen in C900 sintered sample and finer grain size was observed for C930 and C950 sintered samples. C900 sintered sample obtained highest dielectric constant (8617), highest breakdown strength (7.92 kV/cm), highest energy density (2.392 J/cm3).

Study on Palm Oil and Treated Waste Vegetable Oil Impregnated Paper

Oil impregnated insulation paper plays an important role in a transformer as it insulates the windings from high voltage and current. Other than the type of paper used, the properties of oil such as viscosity, relative permittivity and dielectric loss play a major factor that contributes to the quality of the insulation paper. This paper discussed the sonication and esterification process on palm oil and treated waste vegetable oil and its’ effects on the performance of oil impregnated paper. Basically through these processes, viscosity of oils will reduce. However, the resultant permittivity and dielectric loss as well as its’ breakdown strength are rarely reported. Experiments were set to process (sonicates and esterify) the natural oils prior to the paper impregnation process. Results show that esterification is more effective than sonication process in reducing insulation oil viscosity, relative permittivity and dissipation factors as well as increasing the breakdown voltage of the oil impregnated paper. Palm oil methyl ester (POME) could serve as an excellent insulation oil which is very suitable as transformer oil as well as the impregnation medium for paper insulation.

Implementation of a single-stage LED driver using resonant controller

This paper proposes the implementation of a singlestage AC-DC converter using a high voltage resonant controller IC L6598 for driving a street lighting system. The converter is formed by integrating two boost circuits and a half-bridge type LLC resonant circuit. Both boost circuits work in boundary conduction mode (BCM) satisfying the natural function of power factor correction (PFC) of the converter. The soft-switching characteristics of LLC resonant circuit assures the primary side switches to work in zero-voltage-switching (ZVS) mode and the secondary side diodes to work in zero-current-switching (ZCS) mode. This significantly reduces the switching losses and indeed improves the system efficiency. The input voltage is divided by two capacitors resulting in low bus voltage which is allowing the converter to perform well under high-input-voltage. Simulation and experimental results obtained from a 100-W, 240-V AC input laboratory prototype are presented. The result demonstrate that the power factor (PF) of the converter is higher than 0.95, the total harmonics distortion (THD) is lower than 20.5%, and the efficiency is 92.6% at full load.

A single-stage power factor corrected LED driver with dual half-wave rectifier

In this paper, an architecture of a single-stage power factor corrected AC-DC converter controlled by a high voltage resonant controller IC L6598 is proposed as LED street lighting driver. The converter is formed by the integration of two boundary conduction mode (BCM) boost circuits and a half-bridge LLC resonant circuit. The converter adapts dual half-wave rectifiers at the output side that supply same voltage and current value to two separate LED strings. The bus voltage capacitance is greatly reduced and film capacitor is chosen instead of electrolytic capacitors to realize a long lifetime LED driver. With suitable switching frequency, the soft-switching characteristics of LLC resonant circuit assure the zero-voltage-switching (ZVS) of power switches and zero-current-switching (ZCS) of output diodes. This greatly reduces the switching losses and enhances the efficiency of the system. Although the bus voltage is a little bit higher than the input peak voltage, the result obtained from a 140-W laboratory prototype demonstrated that the power factor (PF) is as high as 0.99, the total harmonics distortion (THD) is 15.6%, and the efficiency is 89.4% at 240-V AC input.