Posted to News on 13th Jun 2008, 10:30
Posicon inverter drives include position control functions
Nord Drive Systems is launching a variant of its Nordac SK500 family of frequency inverter drives incorporating sophisticated position control capabilities. Called Posicon, the new functionality supports closed-loop applications with sophisticated motion control features such as the ability to program relative or absolute positioning, synchronising, gearing and S-ramp movement profiles. Posicon makes it both easy and economical to implement a wide range of common industrial automation applications such as feed to length, indexing, precise positioning and synchronising/locking with a remote axis - at 1:1 or another gear ratio.
The Nordac SK500 family of drives for variable-speed control of standard three-phase induction motors spans power output ratings up to 7.5kW, covering a large range of common industrial applications. Drives fitted with Posicon enable users to build systems with closed-loop position and movement control, using feedback from a standard incremental or absolute encoder on the motor shaft or from a remotely mounted encoder. Up to 15 positions can be stored, and the positions are regulated accurately even when faced with large load fluctuations. Positional data can be updated via a fieldbuses network for applications requiring a higher number of positions.
Programming acceleration and deceleration ramps or S-ramp movement profiles can be used to regulate the performance of drives as required in positioning applications. Another intelligent feature is available if the motion required is circular - as in rotary table applications. Here, Posicon can automatically determine the optimum path to the target position to increase productivity.
Programming and teaching
In addition to programming a drive using the inverter's integral man-machine interface, users can employ Nord's PC software package, Nordcon, which is available at no cost. A further 'teach' mode of operation provides a simple means of programming that enables users to move the system to the desired position(s) and capture the data.
Position control commands can be sent from a PLC, over the drive's fieldbus interface (a wide range of fieldbus options are available) or by means of I/O signals from simple hardware such as pushbuttons or a rotary switch.
Inverters in the Nordac SK500 family are equipped with a versatile range of serial, digital and analogue I/O: the minimum complement is RS232 and RS485 ports, five digital inputs and one analogue output, plus two analogue inputs that are reconfigurable as digital channels. Higher-specification inverters offer even more I/O, encoder inputs, plus dual CANopen fieldbus ports for I/O expansion, factory networking, etc. Expansion interfaces on all models enable the inverters to be fitted with alternative fieldbus interfaces including ASi, DeviceNet, Profibus and Interbus - thereby providing a simple means of integrating the equipment with existing factory networks and equipment.
A generous overload capability is available to system builders. Overload currents of 200 per cent can be provided for 3.5 seconds. However, overload currents of 150 per cent can be maintained for a full minute, providing an excellent performance margin. This can be readily exploited by system builders to save costs when automating processes that might require high starting torques, for example, or be exposed to occasional high shock loads.
Nord's UK assembly facility supplies the inverters configured and programmed to suit the application, or pre-assembled with matched motors and gears to simplify an OEM's production processes.
