A Dual-speed Induction Motor as a Source of Electrical Hazard in Operating Conditions of Coal Mine Process Support Areas

Hazardous states of the mine zonal electrical network are caused by the reversed energy flows of induction motors of the energy-consuming equipment in the run-down mode after the power supply is switched off. The electromotive force (EMF) induced in the powered-off stator windings of the dual-speed motors due to the transformer effect also pose a danger of electric shock. The paper presents a methodology and the results of studying the formation of induced EMFs in the powered-off stator windings of dual-speed induction motors, including the run-down mode and the functions that impact on the electromagnetic parameters. Analysis of the impact degree of these induced EMFs on the electrical safety parameters as part of the mine zonal electrical network is presented.

Model-Based Estimation of Transmission Gear Ratio for Driving Energy Consumption of an EV

This paper presents a numerical study of the effect of the transmission configuration on the energy consumption of an electric vehicle. The first part of this study is related to a vehicle simulation model that takes into consideration vehicle resistances such as aerodynamic, rolling and inertial resistance as well as the traction force. The model was then validated by means of vehicle acceleration time, from 0 to 100 km/h in the case of a single-speed gearbox. Vehicle power demand and electrical energy consumption were then evaluated over three standardized test cycles: WLTC-Class 3, NEDC and FTP-75. For each cycle, two cases were studied: a single-speed and dual-speed gearbox. Very different power demand was observed between the cycles in terms of maximum and average driving power. The most power-demanding cycle was WLTC, while NEDC was less power demanding. However, the specific driving energy per kilometer was very similar for NEDC and FTP-75, as it respectively accounted to 0.118/0.116 kWh/km and 0.117/0.115 kWh/km. WLTC led to a higher specific consumption of 0.127/0.124 kWh/km. A dual-speed gearbox led to better efficiency, within the range of 1.7% to 2.4%. The higher value was obtained for highly dynamic WLTC.

Speed and strength of an epidemic intervention

An epidemic can be characterized by its strength (i.e., the reproductive number R ) and speed (i.e., the exponential growth rate r ). Disease modellers have historically placed much more emphasis on strength, in part because the effectiveness of an intervention strategy is typically evaluated on this scale. Here, we develop a mathematical framework for the classic, strength-based paradigm and show that there is a dual speed-based paradigm which can provide complementary insights. In particular, we note that r = 0 is a threshold for disease spread, just like R = 1 [ 1 ], and show that we can measure the strength and speed of an intervention on the same scale as the strength and speed of an epidemic, respectively. We argue that, while the strength-based paradigm provides the clearest insight into certain questions, the speed-based paradigm provides the clearest view in other cases. As an example, we show that evaluating the prospects of ‘test-and-treat’ interventions against the human immunodeficiency virus (HIV) can be done more clearly on the speed than strength scale, given uncertainty in the proportion of HIV spread that happens early in the course of infection. We also discuss evaluating the effects of the importance of pre-symptomatic transmission of the SARS-CoV-2 virus. We suggest that disease modellers should avoid over-emphasizing the reproductive number at the expense of the exponential growth rate, but instead look at these as complementary measures.

Design and Performance Assessment of Dual-Speed Axial Threshing and Separation for Paddy Rice Combines

HighlightsDual-speed axial threshing and separation was designed to improve performance.Loosely connected grains were removed firstly for reducing opportunity for breakage.Machine is complex but a lower effective cylinder speed can reach a good performance.Reasonable feed rate and concave clearance could maintain quality and throughput.ABSTRACT. This research was conducted to assess the performance of a combine, model number 4LZ-4.0 under different threshing functional parameters such as speed of high/low speed cylinder, cylinder-concave clearance and linear speed of concave sieve. An indoor experiment was conducted using the dual-speed axial threshing and separation. These functional parameters were set at five levels. The responses were obtained in terms of broken rate, impurity rate and loss rate. Multi-objective variable optimization was performed using Design-Expert 6.0.10 software. Analysis of variance was done to determine the significant effects of the factor variations on the response values. Design-Expert 6.0.10 software was used to present response surface graphs that were used to describe the variations of the responses as the factors changed from one level to the other. Results showed that with an increase in speed of high/low speed cylinder from 15.42/18.50-22.92/27.50m/s, the percentage of broken rate increased significantly from 0.15% to 1.13%, respectively. At cylinder speeds of 15.42/18.50m/s and 22.92/27.50 m/s rpm, the impurity rate increased from 0.31% to 1.62%, respectively. It was also realized that varying the speed of high/low speed cylinder had a significant effect on the broken rate and impurity rate. The impurity rate increased with an increase in Linear speed of concave sieve from 0.40 to 1.60 m/s, the percentage of impurity rate increased significantly from 0.31% to 1.62% respectively. However, the lowest impurity rate was obtained at an average linear speed of concave sieve of 0.99 m/s. Furthermore, it was realized that increasing the cylinder-concave clearance from 16 to 30 mm, equally increased the percentage of loss rate from 1.78% to 2.93%. From the results obtained, it was suggested that operating the threshing cylinder at a speed of high/low speed cylinder of 18.31/21.97 m/s, cylinder-concave clearance of 22.60 mm and linear velocity of rotary concave of 0.99 m/s, gave a better performance of the machine. Keywords: Axial threshing and separation, Cylinder-concave clearance, Dual-speed, Functional parameters, Linear speed of concave sieve, Speed of high/low speed cylinder.

Innovative and Highly Integrated Modular Electric Drivetrain

A highly integrated electric drivetrain module with 157 kW peak power is presented, which incorporates novel technologies in the field of electric machines, power electronics and transmissions: 1. High-speed electric machine with six phases and injection mould polymer-bonded magnets; 2. High-ratio dual-speed transmission with double planetary gear set (Ravigneaux gear set); 3. Gallium nitride (GaN) power electronics with winding reconfiguration feature.The combination of these components in one single housing makes the drive module flexible to integrate and to combine with conventional or alternative propulsion technologies, thus allowing various hybrid and electric drivetrain topologies. All technologies are selected in accordance with mass production potential and can therefore have a high impact on the automotive market in the future. Currently, the drive module is under development; the first models will be assembled in winter 2019. The integration into a demonstrator vehicle in 2020 will prove the potential of many new technologies and the suitability for the automotive market.