MOTORS AND DRIVES 55
Dc motors deliver higher performance and efficiency
Dc motors are increasing in popularity due to their performance advantages over ac motors for applications ranging from high-speed automation to electric motorbikes. Jon Severn reports on a selection of recent developments in dc motors and drives.
Les moteurs c.c. sont de plus en plus appréciés grâce à leurs avantages en matière de performance par rapport aux moteurs c.a. dans des applications qui vont de l’automatisation haute vitesse aux motos électriques. Jon Severn présente une sélection des développements récents dans le domaine des moteurs et entraînements c.c.
DC-Motoren werden aufgrund ihrer Leistungsvorteile gegenüber AC-Motoren bei Anwendungen von Hochgeschwindigkeits- automation bis zu
Elektromotorrädern immer beliebter. Jon Severn berichtet über eine Rehe von kürzlich erfolgten Entwicklungen bei DC- Motoren und -Antrieben.
T
hree-phase ac induction motors are the most common type of motor used in industrial application, due largely to their simple design, low purchase
cost, reliability and broad choice of sizes and specifications. However, for applications where speed needs to be varied or torque needs to be controlled with high accuracy, brushed dc motors are popular. Where even higher performance and/or reliability are required, brushless dc motors overcome the drawbacks often associated with brushed dc motors. As well as industrial applications, brushed and brushless dc motors are also employed in smaller machines and equipment where speed control is critical – such as computer hard disk drives – or in battery- powered, automotive and other applications where a dc supply is readily available. It should also be remembered that brushless dc motors are non-sparking and therefore do not generate ozone, which makes them suitable for use in medical
www.engineerlive.com
Fig. 1. Intelligent Energy’s ENV motorbike features a hydrogen fuel cell and a high-efficiency Lynch axial-gap dc motor.
applications. Compared with brushed dc motors, brushless types have the further advantage of producing less electrical noise. Today there are several factors behind the
rising demand for dc motors. For example, cars are being offered with more powered devices, plus designers are seeking to improve the performance of the equipment they design, which often entails upgrading from an ac motor to a dc motor. In particular, coreless (ironless) dc motors have low inertia so are useful where high accelerations are required. Interest in alternative energy sources often results in a high- efficiency dc motor being
Fig. 2. The latest version of the Agni Motor offers higher torque per amp and lower speed per volt, as well as being slightly more efficient.
used for the final drive. For example, the prototype ENV motorbike (Fig. 1) from Intelligent Energy features a fuel cell that generates electrical energy from hydrogen and oxygen.
➠
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84