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Flagship drive is `first with standard PLC technology`

01 March, 2003

Flagship drive is `first with standard PLC technology`

Rockwell Automation has added two new members to its PowerFlex family of variable speed drives - a top-of-the-range model which can control induction or servo motors and offers the option of an add-on logic controller, and a general-purpose model which a more powerful variant on the existing PowerFlex 4 drives.

Mark Daniels, Rockwell`s commercial marketing manager for drives in the UK, describes the new PowerFlex 700S as the flagship of the family. An embedded controller based on the Allen-Bradley Logix control engine used in the ControlLogix family of PLCs, can be bolted onto the side of the drive. Daniels says this option, called DriveLogix, makes the 700S the first drive to offer the option of a built-in standard PLC. While other drives offer PLC-type functions, they do not provide standard, off-the-shelf PLC technology, he contends.

With DriveLogix, the 700S can operate either as a standalone device communicating with a central controller, or as an intelligent drive and controller combination in a distributed architecture, eliminating the need for an external controller. The DriveLogix controller uses the same programming environment and languages as other Logix-based products, cutting training, installation and implementation costs.

The 700S, which is available in ratings from 0.37-110kW at 400V, offers selectable motor control algorithms for closed-loop or sensorless operation. It can control either standard induction or servo motors, and can accept a variety of feedback devices, including high-resolution encoders and resolvers.

A built-in position regulator allows the drive to be used for applications ranging from simple indexing to complex electronic line shaft installations. A high-speed, drive-to-drive fibre optic link can transmit synchronised drive and application data between different machine sections within milliseconds.

The 700S drive costs about 15-20% more than the PowerFlex 700 on which it is based. The controller option costs less than an equivalent stand-alone PLC and, according to Daniels, the combination will save about 15% compared to the cost of separate drive and PLC components. It will also require less panel space and will be easier to install and configure.

The other new arrival, the PowerFlex 40, is a more powerful variant on the compact PowerFlex 4, offering sensorless vector control to provide high torque at low speeds, and extending the top power rating from 4kW to 7.5kW. The drive can perform basic logic, timer and counter functions, reducing wiring and hardware costs compared to using an external controller to perform these functions.

A built-in keypad groups the ten most commonly programmed parameters together for easy start-ups. The drive can perform advanced functions such as PID and flying starts, and can accommodate communications cards, such as DeviceNet, internally. Like the PowerFlex 4, the 40 drives can be mounted side-by-side on DIN rails or in panels.

According to Daniels, the PoweFlex family now accounts for more than half of Rockwell`s drives sales. The family will be further extended later this year when the first fruits of Rockwell`s collaboration with Vacon emerge to take PowerFlex ratings above the 110kW mark.

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