Grammar: The Passive Voice. Modal Verbs

Word List:

1. design	конструкция, расчет, чертеж
2. thermal computer aided design	тепловой расчет с помощью компьютера
3. compact motor	малогабаритный двигатель
4. magnet grade	степень намагниченности
5. thermal performance	тепловой режим, тепловые характеристики
6. winding to ambient thermal resistance	обмотка, разработанная  с учетом температуры среды
7. winding current density limit	предельное значение плотности тока в обмотке
8. winding specific electric loading limit	предельное значение удельной электрической нагрузки в обмотке
9. insight	проникновение в суть, понимание сущности
10. gain	экономия, повышение, эффективность
11. to compromise	подвергать риску, опасности
12. to gain	приобретать
13. simple rules of thumb	простые правила “большого пальца”
14. BPM-brushless permanent magnet	бесщеточный постоянный магнит
15. housing heat transfer coefficient	коэффициент теплопроводности корпуса
16. CAD-Computer Aided Design	проектирование с помощью компьютера

Thermal Computer Aided Design – Advancing the Revolution
in Compact Motor

There is currently a revolution in the development of compact brushless permanent magnet (BMP) motors which are up to 75% of the size of conventional products. Such large size reductions are due to a combination of factors including, improved magnet grades, new materials, modern manufacturing techniques and improved design capabilities. Let us concentrate on the improvements that can be gained by using advanced, design capabilities. In particular we will concentrate on the thermal design of motors, a discipline that has traditionally received much less attention than the electromagnetic design.

Traditionally the thermal performance of a new motor design has beenestimated from prior knowledge of one or more of the following parameters - winding to ambient thermal resistance, housing heat transfer coefficient, winding current density limit or winding specific electric loading limit. These numbers may be estimated from tests on existing motors, from competitor catalogue data, or from simple rules of thumb. The problem with such design methods is that no insight is gained of where the thermal design may becompromised and therefore where design effort should be concentrated.

One of the thermal modules of a new commercially available motor design package (Motor-CAD) can be used to give the designer a rapid method of analysing design changes on the thermal behaviour of BPM motors. In doing so, not only can the optimum design solution be quickly identified, but the user fully understands the consequences of changes. It will be used to examine a selection of the thermal issues that may be considered when designing a new motor. It will also be used to highlight some of the improvements that can be achieved by adopting some of the new manufacturing techniques and materials available. Data is presented to illustrate improvements achieved inparticular designs. These values cannot however be generalised to all motors as each design is different and a complete thermal evaluation should be performed on all new designs.

Focused Practice

I. Answer the following questions:

1. What word-combinations do the letters CAD and BPM stand for?

2. What are large size reductions due to?

3. How can the improvements be gained?

4. How has the thermal performance of a new motor design traditionally been estimated?

5. What is the problem with traditional design methods?

6. What can one of the thermal modules of a new available motor design package be used for?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: The revolution in compact BMP motors.

Unit 25

Grammar: The Infinitive

Word List:

1. micro-electro-mechanical systems (MEMS)	электромеханические микросистемы
2. the microbearing device	устройство, опирающееся на микроподшипники
3. power MEMS applications	устройства MEMS большой мощности
4. rig	оснастка
5. microbiaricated rotor	микроротор
6. LIGA=lithography	литография, нанесение металлического слоя
7. induced stresses	обусловленные воздействия
8. rpm=revolutions per minute	об/мин
9. two orders	два порядка, т.е. в 100 раз
10. aircraft propulsion	двигатель летательного аппарата
11. circumferential tip speed	окружная скорость
12. pin bearing	шарнирно-неподвижная опора
13. turbomachinery	турбины
14. viscous drag	вязкостное торможение

Demonstration of a Microfabricated High-Speed Turbine Supported
on Gas Bearings

To achieve high power and efficiency from a rotating device, high circumferential tip speed is a necessity. Conventional scale turbomachinery typically run with tip speeds of order 500 m/s, enabling high-power density applications such as gas turbines for aircraft propulsion and power generation. In order to achieve high levels of power density, microfabricated rotors will need to run at comparable tip speeds. Typical rotating micromachines, such as gears and micromotors, are formed either by surface micromachining or LIGA, supported by solid contact on a pin bearing, and entrained by electrical or contact forces acting on the edges of the rotor. These micro-rotors have reached of order 2 m/s tip speed, which is two orders of magnitude lower than desired for Power MEMS applications.

An effort has been undertaken to develop high-speed rotating devices to enable high-power density MEMS. A single-crystal silicon air turbine supported on gas lubricated bearings has been operated in a controlled and sustained manner at rotational speeds greater than 1 million rpm and power levels approaching 5 W. The device is a second-generation version of the microbearing rig first reported in 1999, and is the first micromachine tooperate at circumferential tip speeds of hundreds of meters per second, comparable to conventional scale turbomachinery. To achieve this level of peripheral speed, microfabricated rotors must withstand large induced stresses, need a sufficient power source to drive them, and require stable, low friction bearings for support. The successful operation of the microbearing device motivates the use of this technology for high-power density MEMS.

The turbine was designed to provide sufficient power to overcome the viscous drag in the bearings and on the back side of the rotor. While viscous drag is relatively large in microsystems due to the small length scale, it is still quite small compared to the capabilities of high-speed turbomachinery. The turbine for the microbearing device had to be intentionally designed to match the relatively low power requirements of the viscous drag. Alternative turbine designs, compatible with the current process and geometric constraints, that produce tens of watts of power (beyond the drag requirements) have been designed for Power MEMS applications.

Focused Practice

I. Answer the following questions:

1. What is necessary to achieve high power and efficiency from a rotating device?

2. How are typical rotating micromachines formed?

3. What effort was undertaken?

4. How has a single-crystal silicon air turbine supported on gas lubricated bearings been operated?

5. Was the operation of the microbearing device successful?

6. What turbine designs have been designed for Power MEMS applications?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: Rotating devices.

Unit 26