Grammar: The Participle. The Absolute Participle Construction

Word List:

Variable Speed Drives

The rapid growth of electrical variable speed drives and the demands for greater precision and economic solutions, has led to a highly competitive market place. Dominated by the rectifier-inverter-fed induction motor drive the market has seen an increase in high performance drives - both vector controlled and direct-torque controlled drives. Speed-sensorless implementations are becoming more widespread along with permanent magnet synchronous motor drives and variations of reluctance motor drives. Intelligent control techniques like fuzzy-, neuro– and fuzzy-neuro will find widespread applications with drive manufacturers concentrating on software development. The possibility of an ‘electronic’ integrated motor and controller could be the next major breakthrough.

The conventional DC motor drive continues to take a considerable share of the variable-speed market. It is predicted to decline, albeit slowly but efforts are being made to reduce costs and enhance reliability. That is not to say that the DC drive market is dead - more that its growth will be slow and its market share will fall.

The power circuit of the general industrial DC drive has changed little since thyristors first came to dominate this application, with the six-pulse fully controlled bridge still being the preferred technology. This might change if legislation to limit the harmonic content of the supply current begins to have an impact on the market.

The induction motor remains the industry workhorse, being both rugged and reliable, it continues to be the preferred choice for the variable-speed drive business. Low cost, coupled with its ease of manufacture, makes it readily available in most parts of the world and it is with the AC drive that most significant innovations will occur. Although better efficiency and low-speed performance could be obtained with permanent magnet synchronous motors there would need to be a dramatic fail in the cost of rare-earth permanent magnet material. So, the position of the induction motor is secure - it has become a global product and is manufactured in nearly every country in the world.

Focused Practice

I. Answer the following questions:

1. What kind of drives has the market seen an increase in?

2. What is becoming more widespread along with permanent magnet synchronous motor drives and variations of reluctance motor drives?

3. Who will intelligent control techniques find widespread applications with?

4. What could be the next major breakthrough?

5. What continues to take a considerable share of the variable-speed market?

6. How much has the power circuit of the general industrial DC drive changed?

7. Why does the induction motor remain the industry workhorse?

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

III. Speak on: DC drives.

Unit 27