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EPL-based drives share DC efficiently

01 January, 2007

EPL-based drives share DC efficiently

After more than three years of development work in the UK, Baldor has unveiled a range of modular three-phase AC drives that use high-speed Ethernet Powerlink (EPL) communications and a shared DC bus system which avoids the need for separate power supplies.

The expandable MotiFlex e100 drives, covering output currents up to 16A (with higher ratings to follow), are suitable for either centralised or decentralised applications. The 100Mbit/s real-time EPL link allows the drives to be daisy-chained, with up to 16 interpolated axes supervised by a single controller.

When several drives share a DC bus, power that is regenerated when an axis decelerates can be used by the other axes, cutting energy consumption. Because each drive has a local capacitor bank, the system`s total capacitance may store enough energy to avoid the need for an external braking resistor.

Instead of the separate power supplies usually needed for shared DC bus systems, the AC-DC converter stage in each drive can supply power not only to that drive, but also to one or more other drives of the same combined rating. In multi-axis applications, this will often mean that that the highest-rated drive can power the rest of the system.

This, in turn, should simplify system building because only one set of contactors, fuses or MCBs, terminal blocks, and one EMC filter, will be needed for the whole system. Many rival systems duplicate the AC components for each drive, or need extra power supplies and capacitor banks — which are often over-sized.

As well as a universal encoder input (for incremental, EnDat, SSI, sin/cos, multi- and single-turn encoders) and I/O (analogue and digital), the MotiFlex drives have two option card slots supporting further I/O, feedback devices, and fieldbuses including Profibus, Modbus, Profinet and DeviceNet. Safety modules are being developed.

There is also a plug-in machine controller, programmed using Baldor`s Mint language, that provides built-in "intelligence", and can control up to three other daisy-chained Motiflex drives to provide low-cost multi-axis automation.

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