Torque-speed Map Research Articles

Customized PMSM Design and Optimization Methodology For Water Pumping Applications

The need to reduce water pumps size to achieve compact designs adapted to multiple working points opens new fields of study. PMSMs are the preferred choice due to outstanding torque-speed range capabilities. This paper presents a methodology to design and optimize PMSMs by defining the desired torque-speed-efficiency map, adapting its performance to the hydraulic characteristics of the water pump. Once the hydraulic efficiency is known, an initial PMSM reference torque-speed-efficiency map is defined according to the objective motor performance, including the distribution of power losses and the power rating of the selected application. The designer has full freedom to define the efficiency levels and distribution along the torque-speed map. The design optimization algorithm achieves the PMSM characteristics which adjust as much as possible to the defined performance. This methodology uses ultra-fast finite element analysis by applying magneto-static computations and a time-space conversion to compute the iron losses, reducing the computational requirements. The torque-speed-efficiency map is calculated by applying a direct-quadrature electrical model. The objective function uses a novel image comparison technique that allows comparing the similarity between the objective and optimized maps. The methodology is validated experimentally by designing and testing a PMSM adapted to a real WP application.

Research on ac copper losses in permanent magnet electrical machines with hairpin windings for automotive applications

In this paper current displacement effects and subsequently ac copper losses in hairpin windings are analyzed in detail for the example of permanent magnet excited electrical machines. The increase of copper losses due to skin- and proximity effects is evaluated across the entire torque-speed map. Their impact on the drive cycle efficiency is discussed for the standardized Worldwide Light Vehicles Test Cycle (WLTC). Moreover, the influence of the rotating magnetic field generated by the rotor’s permanent magnets on the ac copper losses is studied.

Calculation of Maximum Torque Operating Conditions for Inverter-Fed Induction Machine Using Finite-Element Analysis

A procedure to calculate maximum torque operating conditions for the inverter-fed induction machine is proposed in this paper. The proposed procedure minimizes the finite-element analysis computation load by identifying the variation range of stator current and slip frequency for the entire torque-speed map. Thus, the total calculation time for machine steady-state performance estimation can be significantly reduced. The effectiveness of the proposed procedure is validated by an experiment.

Advanced Soft- and Hard-Magnetic Material Models for the Numerical Simulation of Electrical Machines

Accurate modeling of soft- and hard-magnetic materials for the numerical simulation of rotating electrical machines is required to allow predictions on the operational characteristics along the torque-speed map, already in the design stage. The full potential of most appropriate material selection and concurrent geometry adaption can only be utilized if models can represent actual material behavior. The accurate prediction of iron losses of soft-magnetic materials for various frequencies and magnetic flux densities, as well as the degradation due to manufacturing is eminent for the design of electrical machines. Therefore, advanced material models need to be adapted and their accuracy examined to further improve the modeling and enable progression. This paper will give an overview of the current modeling approaches applied at the Institute of Electrical Machines for soft- and hard-magnetic materials in the simulation of rotating electrical machines. A case example in the form of a traction drive is presented to which the models are applied. For the machine modeling, the inhouse solver pyMOOSE is utilized. In order to determine the losses with regard to manufacturing processes, the iron-loss model with material degradation is used in combination with a machine simulation scheme of the entire operating range of the machine. Here, various simulation approaches are combined to form the entire computational toolchain to obtain accurate results in the entire operational range.

Development of a Behavior Maps Tool to Evaluate Drive Operational Boundaries and Optimization Assessment of PMa-SynRMs

The trend in traction motor design and optimization is to achieve high torque and power densities, wider speed range, and high efficiency within the area defining the most frequent operating points. A fast tool to evaluate different variables within the torque-speed map is convenient for this purpose. In this context, starting from a preliminary motor design, and taking into account motor cross-coupling effects and power losses, this paper presents a new tool for evaluating the behavior of permanent magnet machines, such as synchronous reluctance machines, and permanent magnet assisted synchronous reluctance machines, in all operational points. Apart from the torque and efficiency, many other electrical variables can be obtained, such as the current space vector angle, power factor or electrical power among others. The proposed tool also allows optimizing the design of the machine under a pre-established control law, thus obtaining the current set point trajectory in the dq frame and allowing a fast and accurate evaluation of motor performance. The results obtained by means of the proposed simulation tool are compared against finite element analysis simulations and experimental data, thus validating the usefulness and accuracy of the proposed methodology.

Operating Point Resolved Loss Calculation Approach in Saturated Induction Machines

In this paper, the global operating point dependent losses of induction machines are studied by using a local transient loss formulation. The level of flux, the machine is operated at, depends on the operation mode of the inverter. Hence, for precise loss modeling of inverter driven induction machines at the machine design stage, the time and spatial distribution of flux density and the influence of choosing the best operating point is included. A loss scaling method is developed to map iron losses calculated at a single synchronous frequency to other frequencies along the torque–speed map. The modeled losses and operating points are compared to extensive machine measurements. By way of example, the effect of different electrical steel grades tailored either to low losses or preferable magnetizability on the machine performance is investigated.

EV drive efficiency of traction motor considering regenerative braking according to various motor cores

Purpose The purpose of this paper is to study the electric vehicle (EV) drive efficiency of a traction motor considering regenerative braking according to various motor cores. Design/methodology/approach A software program was developed to predict the driving performance of an EV. It determines the driving mileage, the required power of the traction motor, and the operation points on a torque-speed map when drive cycles are given. The driving performance is calculated from the battery capacity, vehicle specification, and efficiency map of the traction motor computed using the finite element analysis. Findings As a result, the motor core is a significant design variable for raising the driving mileage of an EV. It is noted that the change of electrical steels used for the motor core is the lowest priced method of increasing the driving range by 2 km. Originality/value The comparative analysis of motor core by replacing 35PN250 to 25PNX1250F results in improvement effects traveling 4.62 and 5.16 km farther in the Simplified Federal Urban Driving Schedule (SFUDS) and Highway Fuel Economy Driving Schedule (HWFET), respectively. It was also verified that regenerative braking system is able to enhance drive efficiency by 29-31.3 km in the SFUDS and 6.5-7.3 km in the HWFET. From comparison of price rise for increasing driving mileage by 2 km, it is noted that the change of electrical steels used for the motor core is the lowest priced method.

A comparison between Miller and five-stroke cycles for enabling deeply downsized, highly boosted, spark-ignition engines with ultra expansion

It has been well known that the engine downsizing combined with intake boosting is an effective way to improve the fuel conversion efficiency without penalizing the engine torque performance. However, the potential of engine downsizing is not yet fully explored, and the major hurdles include the knocking combustion and the pre-turbine temperature limit, owing to the aggressive intake boosting. Using the engine cycle simulation, this paper compares the effects of the Miller and five stroke cycles on the performance of the deeply downsized and highly boosted SI engine, taking the engine knock and pre-turbine temperature into consideration. In the simulation, the downsizing is implemented by reducing the combustion cylinder number from four to two, while a two stage boosting system is designed for the deeply downsized engine to ensure the wide-open-throttle (WOT) performance comparable to the original four cylinder engine. The Miller cycle is realized by varying the intake valve timing and lift, while the five stroke cycle is enabled with addition of an extra expansion cylinder between the two combustion cylinders. After calibration and validation of the engine cycle simulation models using the experimental data in the original engine, the performances of the deeply downsized engines with both the Miller and five stroke cycles are numerically studied. For the most frequently operated points on the torque-speed map, at low loads the Miller cycle exhibits superior performance over the five-stroke cycle in terms of fuel conversion efficiency, while at higher loads the thermal efficiency of the five stroke cycle, owing primarily to elimination of fuel enrichment operations, is higher than that of the Miller cycle engine. For the WOT operation, even with the two-stage boosting system, at the engine speed below 1700rpm the deeply downsized engine with the Miller cycle fails to deliver the torque comparable to the original engine, while the targeted WOT torque can be achieved with the five stroke cycle engine at all the engine speeds but 800rpm. The mechanism of the efficiency differences between the Miller and five stroke cycles is discussed in depth with the energy balance and influencing factor analysis on thermal efficiency.

Engine model for mapping BSFC contours

Engine manufacturers plot contours of constant BSFC (Brake Specific Fuel Consumption) on torque-speed maps to show those torque-speed combinations at which the engine will operate most efficiently. Conventionally, torque, speed and fuel consumption must be measured at hundreds of points on the map to permit accurate drawing of contours. Both the data taking and the plotting of the contours are very time consuming. Thermal and mechanical efficiencies of an engine were considered in developing a mathematical model that relates torque, speed and fuel consumption. The model can be calibrated to a specific diesel engine by using 40 to 50 experimental obervations of torque, speed and fuel consumption for the engine. Typically, the model can predict fuel consumption to within 1% at most points on the torque-speed map and maximum errors are less than 5%.The model has been extended and programmed to automatically plot contours of constant BSFC and also contours of constant engine power on a torque-speed map.