High-performance ac drive introduction

By Control Engineering Staff September 22, 2005

A700 drive supports most popular communication protocols, including Profibus DP, CC-Link, DeviceNet, ControlNet, LonWorks, Modbus RTU and TCP/IP, Metasys N2, and EtherNet/IP, as well as Mitsubishi Electric’s proprietary RS-485 network.

Advancement and innovation mark a steady stream of new variable-frequency drives (VFDs) coming on the market. One notable introduction this month is A700 high-performance drive from Mitsubishi Electric Automation Inc . This intelligent drive is designed to control ac motors in the 0.5-600 hp range, and replaces the company’s venerable A500 and A500L drives, sold since 1997. The new VFD also is Mitsubishi Electric’s first ac drive with a built-in programmable logic controller (PLC).

A700 drive features special technologies originally developed for Mitsubishi Electric servo drive products—for example, adaptive autotuning, which automatically compensates for changes in load inertia. Benefits include smoother operation, less downtime, and ultimately, lower operating costs.

Using encoder feedback to operate in “flux-vector” mode, A700 drive provides exceptional motor performance; it can generate torque at zero speed, allowing positioning control. With a reported speed response time of 300 rad/s—10 times faster than A500 drive—A700 reacts quickly to sudden load changes with utmost efficiency, according to Mitsubishi.

However, the new drive also can be used without an encoder. Here, A700 relies on newly developed “Real Sensorless Vector” (RSV) algorithm to provide a 200:1 speed range. Its ability to control torque as well as speed makes it ideal for applications where constant tension must be maintained, such as in wind/unwind control, according to the company.

“The A700 is faster, smarter and, more powerful than any standard VFD we’ve ever produced,” says Chris Cusick, marketing manager for Mitsubishi Electric Automation. “And with its built-in programmable logic controller, users can customize the drive to their unique application.”

Frank J. Bartos, executive editor fbartos@reedbusiness.com