The future of AC industrial drives

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Guy Kennett of Mitsubishi Electric explains his vision of how AC drives will develop in the future.

The future of AC industrial drivesEver-more intelligence is being built into drives. Twenty years ago, when drives were a new technology, commissioning typically took two or three days. The cost of this in terms of man-hours and also possibly delayed production could be huge but, in the early-mid 1990s, auto-tuning reduced commissioning time to a matter of hours.

Currently it takes about 10 minutes to get a drive up and running, fully tuned to its motor, and this will continue to be reduced significantly; the function will eventually become one of simply fitting a drive. Critically this will change the culture surrounding drives engineering, and drives will find themselves in a host of new fields of application.

Building services

One massive developing area is in building services. Over the last 10 years drives have been installed in the more sophisticated new buildings - and this trend will be amplified massively by the new Part L of the UK's Building Regulations, which addresses energy efficiency and recommends drives on even the smallest of pumps, fans or blowers.

Drives' increasing intelligence also opens the possibility of local process control. The effect is that drives will adopt some PLC functionality, and indeed several manufacturers already offer such things. Cynics may argue that automation companies will not want to go down this line because it will undermine their PLC sales, while drives-only companies will find it attractive but impossible to source the most up-to-date PLC technologies; in fact the development will be user-driven.

In most cases it will make very little technical difference whether one uses separate PLC or an intelligent drive, the decision will be made by personal preference and custom and practise. Intelligent drives offer advantages where the installation is remote or inaccessible, where space is limited, where local technical capabilities are very low, or where technical capabilities are expensive to implement.

IEC 61131 programming

Within a few years many drives will have IEC 61131 programming capabilities, just like a PLC. However, they will tend to have their intelligence capped at being equal to micro and small PLCs; drives could theoretically be fitted with the capabilities of a large PLC or PAC (programmable automation controller) but this would be unattractive to users who would consider the resultant architecture to be restrictive when it came to later systems reconfiguration.

In recent years the size, performance and reliability of IGBTs, the backbone of a drive's switching capabilities, have advanced significantly. However, further reductions in size are limited due to the constraints of current directives. nonetheless, new technologies may appear that will allow device reduction without impacting on switching performance and long-term reliability.

By combining the control and power electronics, drives can 'map' their motor in real time and thus constantly re-optimise. This is of particular significance because energy saving is fast becoming the number-one reason for installing drives.

20 June 2007

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