Realising the potential of drives

Why should variable speed drives operate as standalone devices when networking enables all their capabilities? It has become commonplace to network PLCs, actuators and sensors in an industrial control system, yet variable speed drives are often left isolated from the network, operating as standalone devices or controlled via point to point hard wiring from the PLC. Network connectivity is becoming more common in drives, but with the launch of the latest products, there are even more benefits to be gained from networked drives.

On one level, the benefits of linking drives to a PLC via a network are straightforward enough. Installation and commissioning times are greatly reduced as wiring is hugely simplified, with multiple connections and complex runs of control cabling replaced by a single network connection. But, more importantly, the arrival of open networks such as DeviceNet, ControlNet and Ethernet/IP in the industrial market has created a real opportunity for using the information available from factory floor automation systems.

Managers, designers and maintenance personnel can now get the information they need when they want it, from anywhere in the world. This will allow manufacturers to revolutionise the way they manage and maintain their production plant. For example, an engineer does not need to be on site to diagnose and correct faults - in today's e-manufacturing environment, machine level data can be accessed from a remote location using a PC running any standard web browser. Managers can base decisions on accurate, real-time plant data, rather than the outdated and incomplete information often available via a typical top-heavy ERP system.

Data captured in the drive such as elapsed run time or elapsed MWh can be shared with computerised maintenance management systems, for example, to enable machine maintenance to be scheduled automatically. Diagnostic data such as output current or drive overload count can also be extracted via the network and used to optimise the drive's performance. In the event of a fault, a drive connected through a modern device level network such as DeviceNet enables drives to be replaced quickly. With standalone or point to point wired drives, the operator gets very little information when there is a problem with a drive. This can mean hours of lost production while the failed drive is located and replaced and the new drive configured to the original settings.

A networked drive, on the other hand, can provide details of the occurrence and exact location of a fault and also give information on the drive's status and the events leading up to the failure. This can be accessed across the enterprise allowing the cause of the failure to be quickly identified. Once the failed drive has been replaced, the latest technology even allows the new unit to be self-configured in minutes using an automatic device replacement feature which uses the scanner card in the PLC to store the drive's original configuration. When the new drive is installed, the scanner card detects it and the correct settings are automatically downloaded without interrupting the network.

Rockwell Automation uses the NetLinx open network architecture to provide this support. NetLinx is a common communication technology which allows plant level devices to connect over DeviceNet to the internet.

By networking the drive, users have a 'virtual window' into it, giving access to metering data, configuration parameters and diagnostic information. Like most other modern automation devices, modern drives are able to capture and share a wealth of valuable data, and accept control and configuration signals, all via a network. By leaving them isolated, users are missing out on this useful feature, which reduces downtime, increases productivity and reduces total costs of ownership.

• Rockwell Automation
  e109@industrialnetworking.co.uk