Smart frequency inverter delivers sophisticated motion control capability

Posicon makes it both easy and economic 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 some gear ratio.

The Nordac SK500 family of drives for variable speed control of standard 3-phase induction motors spans power output ratings up to 7.5 kW, covering a large range of common industrial applications. Drives fitted with Posicon allow 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 remote mounted encoder. Posicon allows users to store up to 15 positions, which are regulated accurately even when faced with large load fluctuations; updating positional data over field buses is available 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.

In addition to programming a drive using the inverter’s integral man-machine interface, users can employ Nord's PC software package, Nordcon, available at no cost. A further 'teach' mode of operation provides a simple means of programming that allows 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 flexible range of serial, digital and analogue I/O: the minimum complement is RS232 and RS485 ports, 5 digital inputs and 1 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 allow the inverters to be fitted with alternative fieldbus interfaces including ASi, DeviceNet, Profibus and Interbus — 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% can be provided for 3.5 seconds. However, overload currents of 150% can be maintained for a full minute, providing a quite exceptional 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 Abingdon, UK assembly facility will supply the new inverters configured and programmed to suit the application, or pre-assembled with matched motors and gears to simplify an OEM's production processes.