Make VFD easy interface with automation systems

As modern variable frequency drives are based on micro-controllers with relatively large memories, there is an opportunity to fit the VFDs with software to provide sophisticated functionality that used to be restricted to DCS or dedicated controllers. The advantage of this software is that it is a tried and tested solution and therefore normally bug free. The other major advantage is that the software provides for standalone functionality and therefore the VFD does not require an interface to any PLC, DCS or automation system. However, this does not mean that any of these automation systems cannot be interfaced to the VFDs because there are plenty of fieldbus interfaces that allow control and monitoring of the VFDs. The most popular of these interfaces in South Africa are Profibus and Device Net. Any signal that is measured or calculated within the VFD is normally available for monitoring by the automation system - thus signals such as torque, power, speed, current, voltage and status are available and independent separate transducers to obtain these signals do not have to be installed.

There are a large number of alternative variable frequency systems available including electrical (ac and dc) and mechanical – each with its pros and cons. The most effective system will depend on the particular application and system requirements.

There is no doubt that there are many advantages, including overall efficiency and production gains, to be had with the use of the correct variable frequency system. Developments in power electronics in recent years have opened many doors leading to very sophisticated VFD and control systems.