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Partial discharge (PD) has been identified as one of the root causes of stator insulation failure even for low voltage (LV) ac motors. For reliable operation of variable frequency drive motors, a standard acceptance test procedure (IEC STD 60034-18-41) to ensure PD-free operation of LV motors was developed. Although the test can verify whether PD exists in the stator for a surge with predetermined voltage level and risetime, the information on where PD activity is present in the stator insulation is not provided. In this article, a test method based on a new variable risetime surge generator is proposed for identifying the component of stator insulation where PD occurs in LV random wound stators. The proposed test allows the user to locate whether PD is in the turn, phase, or ground insulation. This information is critical for lowering the PD inception voltage for improving the motor reliability through insulation system design/manufacturing or motor/drive system reconfiguration. The test is implemented with a 4.5 kV variable risetime surge generator prototype, and seven LV ac motors are tested to show where PD is likely to occur in commercial LV motors.

Temperature and electric field along the stress grading system of a form wound coil under repetitive impulse voltage are studied using 2D axisymmetric and 3D models in COMSOL¯ 5.3a. The validity of the 3D model is shown by comparing the results with the measured temperature profile along the stress grading system. The evaluation of both temperature and electric field shows that using a stress grading system based on a micro-varistor characteristic reduces the maximum temperature; however, with an increase in the electric field, which can be reduced to an acceptable level. An optimization on the initial conductivity of the micro-varistor characteristic confirms that desired electric field and temperature rise are achievable by selecting an optimized conductivity characteristic. 2D and 3D simulations show that a proposed stress grading system, which is a combination of an optimized stress grading tape conductivity and minimum conductive armor tape length, has a good temperature and electrical performances under repetitive impulse voltage.

Background and Objective: Oral candidiasis is often caused by Candida albicans, followed by C. dubliniensis, C. parapsilosis, and C. glabrata. The present study aimed to investigate the antifungal effects of Rosa damascena (R. damascena) essential oil, mixed mouthwash of R. damascena essential oil and grape vinegar, as well as nystatin against various standard Candida species. Materials and Methods: This descriptive study was performed on 5 standard strains of various Candida species. The anti-Candida effects of R. damascena and mixed mouthwash against various Candida strains were assessed using well diffusion and broth macrodilution methods. Nystatin was utilized as a positive control drug. Results: The results of the well diffusion assay of R. damascena essential oil and mixed mouthwash were 17 and 6 mm regarding C. albicans strains, respectively, and 15 mm and 0 regarding other Candida strains, respectively. With respect to the results obtained from broth macrodilution test, the minimum inhibitory concentration of R. damascena essential oil and mixed mouthwash were found to be 8 and 6 µg/ml, 124 and 12 µg/ml, 31 and 12 µg/ml, as well as 62 and 25 µg/ml for C. albicans, C. dubliniensis, C. glabrata , and C. parapsilosis, respectively. Moreover, C. albicans was the most sensitive Candida species to R. damascena essential oil and the mixed mouthwash. Conclusion: The results showed that R. damascena essential oil and mixed mouthwash remarkably led to the inhibition of Candida species growth causing oral candidiasis.

Evaluation of thermal and electrical characteristics of a 13.8 kV rotating machine stress grading system shows that a reduced length of conductive armor tape (CAT) from the slot exit reduces the electric field and temperature rise under pulsed voltage. Although, the electric field in stress grading tape (SGT) increased slightly, with a shorter length of CAT during the rise time of the pulse voltage, it decreased during the DC portion of the pulse voltage. The temperature profile of the stress grading system under pulsed voltage at room, elevated room, and near typical operating temperatures are measured and simulated for several CAT lengths; results show lower temperatures for shorter CAT length. The partial discharge inception voltage is unchanged for shorter CAT lengths. A lower temperature rise is desirable as this leads to a longer life in the absence of partial discharges.

The thermal and electrical characteristics of a stress grading system are studied by simulations and measurements of the electric field and temperature distributions in the overhang region of a form wound medium voltage motor coil. Simulations show that a highly conductive stress grading tape (SGT) reduces the maximum electric field in this region but increases heat production and temperature. In contrast, a highly conductive armor tape (CAT) decreases the maximum electric field in this region and also reduces the heat production and temperature in the stress grading system but also produces a slight increase in the electric field in the SGT region. For the simulation studies, accurate measurements of the electrical and thermal conductivities of materials are made, taking into account the effects of the vacuum pressure impregnation (VPI) process, temperature, and tape builds. The electrical conductivity of single and double half-lap layers of CAT and SGT are measured from 30 to 100 °C. For the evaluation of the simulation model, the temperature profile along the stress grading system was measured and simulated under pulsed voltage at room and near typical operating temperatures.

The aim of this study is to evaluate the anticandidal effects of essential oils derived from fennel (Nystatin (44 μg/mL) had the strongest antifungal effect, followed by cumin [minimum inhibitory concentration (MIC) = 662 μg/mL; minimum fungicidal concentration (MFC) = 630 μg/mL] and fennel (MIC = 1,074 μg/mL; MFC = 1,227 μg/mL). The average diameter of the fungal growth inhibition zone was 23 mm for Nystatin, 14 mm for cumin essential oil, and 5 mm for fennel essential oil.The anti

IEC 60034-18-41 has been developed as a standard acceptance test to ensure partial discharge (PD)-free operation for improving the reliability of low voltage (LV) variable frequency drive (VFD) motors. Although the test can verify whether PD exists in the stator for a voltage surge with predetermined magnitude and risetime, the information on where PD activity is occurring in the stator insulation is not clearly given. In this paper, a method based on variable risetime surge voltage testing is proposed for identifying the component of the stator insulation system where PD occurs in LV random wound motor stators (turn, phase, or ground insulation). This information can be used for increasing the PD inception voltage for improving the reliability of the motor through insulation system design/manufacturing. The test is implemented with a 4.5 kV variable risetime surge generator prototype. 4 LV ac motors are tested to show where PD is likely to occur in commercial LV motors.

Simulation studies under pulse voltage using a 2D axisymmetric model in COMSOL® 5.3a on the temperature and electric field along the stress grading system (SGS) of a form wound coil are reported in this work. The validity of the 2D model is shown by comparing the results with the measured temperature profile along the SGS. The effect of the nonlinearity of stress grading tape (SGT) conductivity is evaluated on both temperature and electric field. The results show that increasing the level of the nonlinearity of the SGT conductivity reduces the maximum electric field. On the other hand, the temperature rise is decreased by reducing the level of the nonlinearity of the SGT conductivity. As such, the effect of nonlinearity changes are not mutually compatible in controlling both the electric field and temperature profiles.

Surface partial discharges on the stress grading system of a medium voltage form-wound coil fed by an inverter can lead to insulation failure. Reducing the maximum surface electric field is therefore essential for prolonging insulation life. Under square waves in simulations using COMSOL Multiphysics, this work studies how floating metal foils added to the stress grading tape (SGT) affect electric field and temperature distributions. The results show that the metal foils make the electric field uniform but increase the temperature, due to increased current density in the stress grading tape. However, the temperature rise is below that considered to be detrimental to the insulation.

Limiting the temperature rise in the stress grading system in a medium voltage form-wound coil of a rotating machine driven by an adjustable speed drive is essential to prolong the life of a motor. The common way of increasing the electrical conductivity of the system, thereby to lower joule heat production and temperature rise, is to increase the build of the tape system. Simulation studies on various stress grading system builds on the heat production has been evaluated in this study. A good correlation between measured and simulated temperature profiles under pulse voltage condition confirms the validity of the simulation. The stress grading system has been simulated using the 2D axisymmetric module in COMSOL® 5.2a. The results show that increasing the number of layers of conductive armor tape can reduce the heat production in CAT region but by increasing the number of layers of stress grading tape leads to increase in heat production in SGT region. The study suggests that use of other non-linear tape materials for SGT may be needed to effectively lower the temperature rise in the stress grading system.

Evaluating the performance of the stress grading system by simulating the electric field and potential distributions in the overhang region shows that high conductive stress grading tape (SGT) reduces the maximum electric field at this region. For simulation studies, an accurate conductivity that takes into account the effects of vacuum pressure impregnation (VPI) process, temperature, and tape builds is measured. As the electric field on the SGT is enhanced under operating conditions, the conductivity of the SGT has been measured in a high electrical field condition under pulse conditions to minimize the effects of temperature rise on the SGT. The conductivity of a one half-lap layer and a double half-lap layer of SGT at different temperatures is measured. The results show that for both designs, the higher the tape conductivity the lower the maximum electric field in the SGT region. For evaluating the simulation model, the temperature profile along the stress grading system is measured and simulated under high frequency sinusoidal voltage.

Measurements of the electrical conductivity of conductive armor tape (CAT) applied to medium and high voltage motor form wound coils, having various tape builds and constructions, show conductivities that differ significantly after vacuum pressure impregnation (VPI). Tape builds consisting of a single half-lapped layer and a double half-lapped layer are studied at 30 and 100 °C. Electrical conductivity in both surface and transverse directions show significant difference before and after VPI. This demonstrates the importance of using measured conductivity after VPI for simulation studies. Simulations for pulsed voltage with 1 µs rise time show that higher CAT conductivity increases the electric field in the stress grading tape layer.

Summary Objective The in vitro antifungal activities of essential oil from Cuminum cyminum ( C. cyminum ) and alcoholic extract from Salvadora persica ( S. persica ) were investigated in order to evaluate their efficacy against C. albicans ATCC 14053, C. dubliniensis ATCC CD60, C. glabrata ATCC 90030, C. krusei ATCC 6258 and C. parapsilosis ATCC 22019. Methods The essential oil was obtained by hydrodistillation in a Clevenger apparatus and analyzed by gas chromatography/mass spectroscopy (GC/MS). The disc diffusion and broth macrodilution methods were used as antifungal susceptibility tests. Results The GC/MS analysis allowed 17 components to be determined; the main constituents of C. cyminum essential oil were α-pinene (30%), limonene (21%) and 1,8-cineole (18.5%). C. cyminum oil had a broad-spectrum antifungal activity against different pathogenic Candida species. Inhibition zone values ranged from 7 to 50 mm for C. cyminum and 0 to 10 mm for S. persica against the organisms tested. The best minimal inhibitory concentration (MIC) of C. cyminum oil was associated with C. albicans and C. dubliniensis (289 mg/L) and the MICs of S. persica extract were 4.9 mg/mL and 20 mg/mL against C. albicans and C. dubliniensis , respectively. Conclusion The results suggested the potential substitution of the antifungal chemicals by C. cyminum essential oil and S. persica alcoholic extract as natural inhibitors to control the growth of the most important pathogenic Candida species and alternative therapies for candidiasis.

Summary Objective To investigate the anti-Malassezia activities of Zataria multiflora, Pelargonium graveolens and Cuminum cyminum essential oils (EOs) against different pathogenic Malassezia species isolated from patients with pityriasis versicolor (PV). Patients and methods The EOs were obtained by water-distillation using a Clevenger-type system. Anti-Malassezia activity against Malassezia species was carried out using disk diffusion method in Dixon agar. Results The main oil components were carvacrol (61.3%) and thymol (25.2%) for Z. multiflora, αpinene (30%) and limonene (21%) for C. cyminum and citronelol (28.2%) and geraniol (22.1%) for P. graveolens. The three Malassezia species showed a similar susceptibility to the three plants tested, C. cyminum (mean value: 48.3 mm) being the most active, followed by Z. multiflora (mean value: 28.1 mm) and P. graveolens (mean value: 26.1 mm). Conclusion This study indicated that Z. multiflora, P. graveolens and C. cyminum EOs have considerable anti-Malassezia activities, deserving further investigation for clinical applications for the treatment of PV.

Summary Objective Essential oils (EO) of five medicinal plants were tested for anti-Fusarium activity against 10 non-toxigenic (Fusarium solani and Fusarium oxysporum) and 11 toxigenic (Fusarium verticillioides, Fusarium poae and Fusarium equiseti) isolates. Materials and methods Different dilutions of EO were prepared and 5 × 103 conidia of each fungal suspension were inoculated into Sabouraud's glucose broth tubes. The cultures were incubated at 28 °C for 4 days. Results Mean concentrations of the EO of Zataria multiflora (165.4 and 88.9 μg/ml), Cuminum cyminum (159 and 185.3 μg/ml), Foeniculum vulgare (496.4 and 532.9 μg/ml), Pinaceae (869.7 and 852.43 μg/ml) and Heracleum persicum (753.5 and 1492.6 μg/ml) completely inhibit all the non-toxigenic and toxigenic isolates, respectively. Z. multiflora and H. persicum showed the highest and lowest activity against toxigenic Fusarium isolates, whereas C. cyminum and H. persicum had the highest and lowest effect on non-toxigenic isolates, respectively. However, F. vulgare and Pinaceae had moderate effects against tested fungi. Conclusion The results indicated that non-toxigenic and toxigenic Fusarium isolates were sensitive to the five EO, particularly sensitive to C. cyminum and Z. multiflora, respectively.

Summary Objective To screen anti- Candida albicans activity of the essential oils of 16 Iranian medicinal plants. Materials and methods Anti- C. albicans effect of plant oils, amphotericin B, nystatin and ketoconazole were determined by disc diffusion and broth macrodilution methods. Results Fourteen (87%) out of the 16 plants were found to be active. These oils confirmed the existence of a significant activity against C. albicans tested with minimal inhibitory concentration (MIC) values ranging from 150 to 2300 μg/ml using broth macrodilution method and the growth inhibition zone ranging from 16 to 55 mm using disc diffusion method. The essential oils of Zataria multiflora, Thymus kotschyanus, Cuminum cyminum and Plargonium graveolens showed significant activity against C. albicans ( P Conclusion The oils that showed strong anti- Candida activity are worth of further investigations in order to identify the active compounds and their clinical applications for the treatment of candidiasis.

Macrophages have an important role in host defense against fungal infections such as candidiasis. Active components such as polysaccharides, lectins, proteins, and peptides present in plants have been shown to stimulate the immune system. The aim of this study was to investigate the immunostimulatory effects of water, ethanol, and acetone extracts of Ziziphora tenuior (Z. tenuior) on murine peritoneal mactophages in vitro. Murine peritoneal macrophages were treated with different concentrations of Z. tenuior extracts. The viability of macrophages and nitric oxide production were evaluated using 3-(4, 5-dimethylthiaozle-2-yl)-2, 5-diphenyle-tetra zolium bromide (MTT) assay and Griess method, respectively. In addition, the reactive oxygen species (ROS) production and fungicidal activity were evaluated by nitrobiue tetrazolium (NBT) assay and killing method, respectively. A significant increase in macrophage activity was observed with water extract of Z. tenuior (P < 0.05). Moreover, this extract showed a significant inducing effect on the levels of ROS and a strong fungicidal activity in treated macrophages at concentrations of 10 and 20 mg/ml (P < 0.05). In conclusion, Z. tenuior extract demonstrated significant immunostimulatory activity using MTT, NBT, and killing assays on Candida albicans. To clarify the exact machanisms of this activity, more studies should be performed with isolated immunostimulatory components.

Background: The immune system provides protection against infectious diseases that are caused by various microorganisms, in particular pathogenic fungi. Utilization of herbal immunostimulants is one solution to improve the immunity of humans and to decrease their susceptibility to infectious diseases. Objectives: The current study aimed to investigate the immunostimulatory effects of the aqueous extract of Heracleum persicum on mouse peritoneal macrophages. Materials and Methods: The present in vitro study investigated the effect of the aqueous extract of H. perscium on the viability of macrophages and nitric oxide (NO) production using microculture tetrazolium (MTT) assay and Griess method, respectively. The effects on fungicidal activity and reactive oxygen species (ROS) production of stimulated peritoneal macrophages were also studied using killing method and nitroblue tetrazolium (NBT) assay, respectively. Results: The aqueous extract of H. persicum (Hp-W) at concentration of 10 mg/ mL resulted in a significant increase in NO production (8.17 nmol) by macrophages (P < 0.05). Moreover, H. persicum had a stimulatory effect on the level of ROS (P < 0.05) and a strong candidacidal activity in macrophages treated with 20 mg/ mL of the extract (P < 0.05). Conclusions: The aqueous extract of H. persicum showed a significant immunostimulatory activity on macrophages. To clarify the exact mechanisms of this activity, more studies should be done with purified immunostimulatory components of H. persicum in future.