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Decentralised duo offers benefits in two parts

01 July, 2002

Decentralised duo offers benefits in two parts

Danfoss has announced a pair of products designed to tap the growing demand for decentralised controls for multi-motor installations. The products - an AC variable speed drive, and a fixed-speed controller - both have a two-part construction, with a base section where all the connections are made, and a control section which plugs into it. This approach is said to make installation and servicing easier and quicker.

The variable speed range - the VLT Decentral FCD 300 - is a totally enclosed frequency converter that can be mounted on or near the motor. Power cables can be looped in the base section and control cabling is simplified by using RS485, Profibus or AS-i bus systems. The control section can be commissioned off-line on a workbench and fixed to the base on site using four screws.

The drive and motor are protected against hazards such as high temperatures and mains loss. Protected motor brake control is included.

The IP66-protected VSD is available initially in ratings up to 3kW. The die-cast case is designed to fit the terminal box of any standard IEC cage motor and is coated with an anti-corrosive finish designed to withstand hosedowns on food production lines.

The second new arrival is a fixed-speed controller that provides functions such as soft-start, reversing, mechanical brake control, and thermistor and electronic control via an AS-i interface. Profibus is available as an option on the Decentral Motor Switch DMS300, and a DeviceNet option is planned.

The controller, for cage motors up to 3kW, is available initially in five models ranging from a simple unidirectional version with thermistor control, through to a sophisticated version offering fieldbus control. There is space in the base section for an isolating switch to provide full galvanic isolation of the motor without needing a separate enclosure.

The two-part design allows Danfoss to offer special versions with features such as pluggable motor and sensor connections for large OEMs and volume buyers. In one of the first applications for the new controllers, BMW has ordered more than 450 for a project in Germany.

Decentralised motor controls are becoming increasingly popular in large installations. They dispense with the need for a central control cabinet and its expensive cabling.

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