High Output Torque Research Articles

Improving Transient Performance of Reluctance Motors

Reluctance motors have a wide range of industrial applications. This is due to speed constancy and reliability in operation, as it is connected directly to the AC supply and operated at synchronous speed. Steady-state performance of this type of motors is extensively examined to get high output torque, improved power factor and extended stable region. Transient performance of reluctance motors has received relatively less attention. Previous emphasis was mainly on examining the effects of motor inertia, incorrect motor design parameters and number of pole slipping. A numerical technique has recently been applied to model damping and synchronizing torques of reluctance motors, and full analysis of dynamic performance is achieved [1]. This indicated that there are optimum values of electrical parameters which effectively give maximum damping to hunting oscillations and improve the dynamical performance. This leads to an extra attention being concentrated on how transient performance is affected by these electrical parameters which is the subject of this paper. The paper investigates the effects of all electrical parameters on transient performance and find out which parameters improve motor transients. Damping torque is modeled and the optimum values of electrical parameters, which give maximum damping to hunting oscillations, are given. The effects of these parameters on motor transients, following transient load increase and during starting conditions, are extensively studied. The study covers motor operation from either nominal or variable supply voltage and frequency.

The BMW ETA Engine Concept

The desire to conserve mineral oil reserves has resulted in drastic increases in the cost of fuel which has become the predominant factor in operating cost criteria. Thus intensive efforts are being made throughout the automotive industry to reduce fuel consumption. Next to minimizing resistance forces, the optimization of engine and transmission offers the greatest potential for achieving this goal. For spark ignition engines this is best achieved by adapting the most efficient engine parameters to coincide with the general operating conditions. The BMW Eta engine concept when compared with current engine characteristics gives a comparable vehicle performance at considerably lower engine speeds with higher torque output. In general operating conditions this results in fuel savings of up to 15 per cent.

New Family of High-Ratio Reduction Gears with Multiple Drive Paths

A new family of high-efficiency, high-ratio reduction gears is described in which a counter-rotating epicyclic gear distributes power equally between two, three or four parallel drive paths. The mechanisms employ zero stiffness torque-balancing within and external to the epicyclic unit and work within a spectrum of operation bounded by designs having a fixed annulus or a fixed planet carrier. A theory is developed to investigate the principal design problems associated with reduction ratios, bearing speed, centrifugal loading, bearing life and epicyclic efficiency. A primary application is to high-output torque transmission systems such as those used in helicopters.

Auxiliary Equipment

De Havilland Propellers Ltd., Hatfield, Herts, have developed a series of torque motors for applications where absolutely reliable operation, together with high torque output and frequency response, low weight and compact size, are of paramount importance. The torque motors provide a mechanical energy output proportional to an electrical input signal; they have been designed specifically to operate control valves in hydraulic and pneumatic servo actuators, but are suitable for recording instruments and many other duties. Provision is made for differential or series excitation; differential excitation is recommended as it eliminates datum shift due to supply variations. A torque, which is proportional to the input current, is developed at the output shaft and this, in conjunction with the stiffness of the system, produces a proportional shaft deflexion.

A self-balancing transformer-core-loss bridge

Measuring transformer core loss by impedance bridge methods offers a number of advantages over conventional wattmeter methods, particularly in automation. Human errors are minimized and test accuracy is improved. The bridge is self-balancing and control can be effected either by manual or punched card programming. Direct readings, high precision, and high output torque make the self-balancing bridge particularly suitable for automation.