Idle Losses Research Articles

Torque Distribution Strategy for a Front- and Rear-Wheel-Driven Electric Vehicle

Electric vehicles (EVs) with a distributed drive train configuration offer great potential and flexibility for improving system efficiency, performance, reliability, and safety. This paper investigates a torque distribution scheme for a front- and rear-wheel-driven microsized EV to improve drive train efficiency over a wide torque and speed range. The loss model of the traction permanent-magnet (PM) motor is characterized in both the constant-torque and flux-weakening regions. The relationship between motor efficiency and torque at a given speed is then derived. It has been shown that maximum efficiency is achieved if the total torque required by the vehicle is equally shared between the two identical motors. In addition, the distribution of the energy consumption over a New European Driving Cycle (NEDC) is analyzed, and the regions of high speed and low torque are identified to have a high level of energy consumption; in these regions, motor efficiency improvement is the most important. Therefore, this paper further proposes to operate just one motor to provide the total required torque in the low-torque region. A clutch may be employed between one motor and gearbox (differential), thus “switching off” its idle loss (no-load loss and flux-weakening loss) and improving drive train efficiency. An online optimized torque distribution algorithm has been devised based on the motor efficiency map to determine whether the second motor should be disengaged by the clutch in the low-torque region. With the proposed optimization scheme, drive train efficiency can be improved by 4% over the NEDC. Experimental test results validate the proposed torque distribution strategy.

Design Methodology of Camshaft Driven Charge Valves for Pneumatic Engine Starts

Idling losses comprise a significant amount of the fuel consumption of internal combustion engines. Therefore, shutting down the engine during idling phases can improve their overall efficiency. For driver acceptance a fast restart of the engine must be guaranteed. A fast engine start can be realized using a powerful electric starter and an appropriate battery which are found for example in hybrid electric vehicles. However, these involve additional cost and weight. An alternative method is to use pressurized air stored in a tank that can be injected directly into the cylinders to start the engine pneumatically. In this paper pneumatic engine starts using camshaft driven charge valves are discussed. A general methodology for an air-optimal charge valve design is presented which can tackle various requirements. The proposed design methodology is based on a process model representing pneumatic engine operation. A design example for a two-cylinder engine is shown and the resulting optimized pneumatic start is experimentally verified on a test bench engine. The engine's idling speed of 1200 rpm can be reached within 350 ms for an initial pressure in the air tank of 10 bar.

Synthesis of broadband and flat parametric gain by idler loss in optical fiber

Besides dispersion engineering, idler-band distributed fiber loss provides a new synthesis freedom to flatten and broaden the gain spectrum for a fiber-optic parametric amplifier. This interesting phenomenon is based on the fact that the power balance between signal and idler is broken by idler loss, which changes the power conversion process in four-wave-mixing. The pump-to-signal conversion efficiency is kept unchanged in spite of the loss.

An improved epon upstream transmission scheme with zero inter-period idle loss

Existing Ethernet Passive Optical Network (EPON) Dynamic Bandwidth Allocation (DBA) algorithms suffer from the disadvantage of idle time loss, which lower the upstream bandwidth utilization. This letter proposes an improved upstream transmission scheme with idle-time eliminating mechanism. Theoretical analysis and numerical calculation prove that the improved scheme can effectively eliminate the idle time and enhance the efficiency of upstream link utilization. Simulation results have shown that the bandwidth utilization can be raised up to 15% in heavy-load scenarios while the time delay performance of Assured Forwarding (AF) and Best Effort (BE) services are improved simultaneously.

Test Results of a Compact Disk-Type Motor/Generator Unit With Superconducting Bearings for Flywheel Energy Storage Systems With Ultra-Low Idling Losses

A 3 kW experimental disk type permanent magnet motor/generator - designed for a superconducting flywheel energy storage system - was constructed and tested. The special design of the machine itself aimed to decrease the no-load losses so that they become equal or less than the losses of the superconducting bearing itself. To achieve this, no-load losses had to be decreased by several orders of magnitude compared to the similar losses of ordinary machines. Hence, we applied a special double-rotor, ironless stator construction, with copper windings made of Litz wire. The machine is equipped with its own axial flux superconducting bearing consisting of several permanent magnet rings within each other. The compact rotor of the machine and the bearing itself rep resents a stored energy of 50 kj, so it could be tested without additional flywheel parts in a vacuum chamber. In this paper we introduce spin-down test results of the above machine at different vacuum levels. On the basis of the measure ments it was possible to separate the loss components such as hysteresis, eddy-currents and windage.

An At-All Operating Points Highly Efficient PMSM for HEV

Average losses of the electric drive throughout a driving cycle are an important issue for hybrid electric vehicles. Permanent magnet synchronous electric motors (PMSM) are the most efficient electric drives under load conditions. However, they suffer from idle losses at high speed and low load, which is a typical operating condition in highway cycles. This leads, in some cases, to even higher fuel consumption of HEV vs. conventional vehicles.As well designed permanent magnet machines for HEV usually have excellent efficiency at operating points close to their rating, the main focus of the presented work is achieving an improvement in no load and reduced load conditions. Such losses will occur at high speed and low load, because the PMSM creates an induced voltage exceeding the battery voltage, which must be compensated by an inductive voltage drop through the motor inductance by a purely reactive current causing losses.A proposal for a special design for PMSM with regard to the ability of active reduction of those losses at high speeds is made in the following comment: The compensation current depends on the motor inductance. Obviously, a high inductance in the axis of magnetization needs a low compensation current, whereas a low inductance in the quadrature-axis results in a large constant power range. So a special design of an asymmetrical PMSM has been developed in order to achieve minimum idle losses.

Efficient method for eddy current analysis in permanent magnets of electric motors

This paper presents an efficient method for eddy current analysis in permanent magnets (PM) used in electric machines. Due to appreciable electric conductivity of sintered PM the energy losses related to induced eddy currents cannot be neglected. Since the resulting increase of temperature may weaken the magnetomotive force or even demagnetize the PM material. Two numerical approaches for eddy current calculations in massive materials are commonly applied: 2d model (assuming infinite axial length) and 3d model (usually suffering from numerical inefficiency). In this paper we discuss numerically efficient method for eddy current computation taking actual axial length into account. We propose to extend the 2d field-circuit-motion time-stepping model to 3d model of induced electric field in the area of massive conducting elements, for instance, the PM of electric motor. Design study of a brushless dc motor is presented. During numerical experiments two contributions to the PM losses are characterized: idle run losses due to stator slotting, and armature reaction losses due to high frequency current switching. The influence of the PM segmentation on the eddy current losses is studied.

Flywheel energy storage advances using HTS bearings

High-temperature-superconducting (HTS) bearings have the potential to reduce rotor idling losses and make flywheel energy storage economical. Demonstration of large, high-speed flywheels is key to market penetration, Toward this goal, we have developed and tested a flywheel system with 5- to 15-kg disk-shaped rotors. Rim speeds exceeded 400 m/s, and stored energies were >80 Wh. Test implementation required technological advances in nearly all aspects of the flywheel system, Features and limitations of the design and tests are discussed, especially those related to achieving greater energy storage levels.

Energy efficiency of office equipment in commercial buildings: The case of Thailand

We present results of a study on energy-saving potential for office equipment including personal computer (PC) systems, printers, copiers, and facsimile machines in Thailand. Field surveys were undertaken to assess energy consumption in commercial buildings. The load patterns were monitored to determine the times spent in active, standby, suspend, and off modes. These data were combined with estimated diversity factors and power measurements in each mode to find the annual energy consumptions and energy-savings potentials. Idle losses are 53% for PC systems, 94% for copiers, 96% for dot matrix and ink-jet printers, 98% for laser printers, and 98% for fax machines. Office equipment accounts for only 2.2–5.6% of total energy consumption in the buildings audited; up to 25% of this annual energy consumption can be saved without extra costs. If all commercial buildings in Thailand have similar use patterns, the annual energy con- sumption and commercial peak-demand savings will be of the order of 700 GWh and 200 MW, respectively, by the year 2005.

Optical parametric oscillators without phase matching

We show that optical parametric oscillators (OPO's) based on intersubband transitions in quantum wells operate in a new and interesting regime where the gain, loss, and momentum mismatch are all of the same order of magnitude. We find that such OPO's can oscillate without phase matching. The threshold gain does not increase monotonically with idler loss, as one would expect intuitively, but experiences a minimum. This minimum comes about because of a relaxation of the momentum selection rule or phase-matching condition. We derive these results by analyzing an OPO without making any of the usual assumptions on the relative magnitudes of the gain, loss, and momentum mismatch. We also consider in detail the design of a particular quantum-well structure, the asymmetric double quantum well, for realizing such an OPO experimentally.

Evaluation of fuel consumption rates and thermal efficiency of automobiles by application of furnace analysis

Analysis of automobile fuel consumption data reported by Cope (1973) has shown that behavior obeys a simple relation between fuel consumption rate (in gal/hr/) and speed (in m.p.h.) for all vehicles tested, with and without air conditioning, with vehicles differentiated by different experimental values of three equation constants: an intrinsic efficiency parameter, a theoretical maximum velocity, and the idle consumption. These parameters determine the optimum speed for the best m.p.g. The results show that the optimum speed increases with idle losses; however, the proportional efficiency also falls. The effect of some other factors can also be identified in the equations and parameter values: air conditioning, for example, can have a large effect on a small engine or on a highly tuned engine in a light weight car, but quite minor effect on a large engine in a heavy car. Implications for the future are also discussed.

Linear time-varying circuit analysis of the step-recovery diode harmonic generator†

Abstract Linear time-varying analysis of the step recovery diode harmonic generator is investigated to assess its value as a means of obtaining a very general and flexible technique for the evaluation of the circuit properties without recourse to analogue computation procedures. The approach is used to evaluate the effects of diode transition time and conducting resistance, and of source and terminating impedances and bias (conduction time). The effects of idler circuits on efficiency and terminating impedances are readily evaluated and the influence of idler loss characterized in a number of idler combinations for high-order multipliers. The effects of finite output circuit Q are also shown.