More power for ac motor drives

Paul Boughton

Baldor is greatly extending its H2 family of ac motor drives for adjustable-speed applications with new higher power options, washdown-duty variants, and more plug-in expansion cards.

Highlights include 26 new ac motor drives that extend the upper power rating from 45 to 93 kW, a further selection of drives available in washdown-duty enclosures, and a programmable 'pulse-follower' board that allows users to link drives in sophisticated ways - including electronic gearing.

One of the key features of Baldor's new H2 drive family is its focus on reliability. This results from a high-integrity design strategy which includes FMEA (failure mode and effect analysis), built-in protection modes to guard against misuse, and a manufacturing process embracing stress testing and full-load testing of final products.

With over a year of sales history for the lower power options, this careful design approach has resulted in a repair returns level of less than 0.3 per cent - said to be an exceptional figure for this area of power electronics - providing valuable support for automation users with critical or continuous processes.

H2 drives are available in open- or closed-loop variants, supporting inverter, encoderless vector and closed-loop vector modes of motor control. There is also a range of drives for servo motor control applications up to 18.5 kW.

The closed-loop variant features a fourth-generation space-vector control algorithm for fast and steady motor control as temperature and loading conditions fluctuate. This sheer choice of speed control, combined with a modular expansion bus and option range, provides optimised packages for adjustable-speed motor drive applications, from simple-speed control to advanced positioning and sophisticated movements.

Positioning software is included with the new drives; this supports 15 different profiles as standard, including point-to-point moves, without the need to install any additional hardware.

The drives all feature an expansion bus that accepts plug-in functions including communications facilities or digital and analogue I/O cards. This allows users to configure systems for specific applications at minimal cost. Among the fieldbus networking communications options are Devicenet and Profibus-DP, with Modbus as standard, and Ethernet TCP/IP networking. The latter option can function as an HTTP web server, allowing remote monitoring of status using a standard web browser. The card slots also allow a drive's I/O capability to be expanded economically for more sophisticated automation applications. Among a number of new choices in this area are analogue I/O cards with 16-bit resolution, and a programmable pulse follower card that allows a drive to operate in synchronisation with another drive or encoder. This latter option also includes a scalable output to another drive or control system, and the ability to change ratios on the fly to accommodate 'slips' on a web processing line.

The latest members of the H2 family extend the power ratings available from 45 to 93 kW, opening up applications in a number of heavier-duty machinery areas such as extruders or punch presses. Baldor is also adding a choice of units up to 7.5 kW power ratings in washdown duty enclosures, for clean-area applications such as food and pharmaceutical processing. Inverter, encoderless vector and closed-loop vector models are available for single- and three-phase inputs of 230, 460 or 575 V ac.

The H2 drives continue Baldor's tradition of ease of use, with removable keypad controllers that employ the same high-level language as Baldor's previous H family. Using the keypad, which gives access to built-in positioning software, control programs can be set up with ease. With this release of further family members, this ease-of-use feature is enhanced with the availability of Baldor's Windows-based Mint Workbench programming environment, the same software tool used across Baldor's range of motion controllers and servo drives. Among the sophisticated drive configuration and management features this brings is a 'software scope' tool that allows users to tune and verify the motor control profile performance without connecting an oscilloscope.

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