Posted to News on 5th Feb 2008, 17:09
Compact frequency inverters handle 200 per cent overload
A new family of compact frequency inverters from Nord Gear UK can be adapted easily to suit specific applications, from simple speed control of AC motors to complex movement automation. A novel 200 per cent overload capability allows a smaller inverter drive to be selected in many cases, cutting as much as 10 per cent off typical equipment costs. Motor torques of 200 per cent nominal level can even be delivered at zero speed. This level of performance and precision control can, in many instances, enable low-cost AC motor equipment to be used in place of much more expensive motion controller and servomotor-based automation.
This new inverter family spans power output ratings from 0.25-7.5kW, covering a large range of common industrial applications, and comes complete with integrated RFI filters. Units can be selected and configured to provide simple V/Hz control of motor speed or more sophisticated sensorless current vector operation - with optional encoder feedback for full closed-loop control. Optional software allows units to be used to perform precision positioning tasks. Moreover, Nordac SK500 inverters can store up to four complete programs, so systems can be reconfigured in seconds for different control functions or production routines.
All Nordac SK500 family inverters are equipped with a flexible 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 allow the inverters to be fitted with alternative fieldbus interfaces including ASi, DeviceNet, Profibus and Interbus, which provides a simple means of integrating the equipment with existing factory networks and devices.
Overload current performances
The generous overload capability of Nordac SK500 family inverters is particularly useful for system builders. Overload currents of 200 per cent can be provided for 3.5s. However, overload currents of 150 per cent can be maintained for a full minute, providing an 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.
On higher-specification models a valuable built-in 'safety stop' function complying with the EN 954-1 standard is available. It can be used to implement either category 3 (single-channel stop) or category 4 (dual-channel stop). This is useful for isolating the motor from the frequency inverter, or for isolating the motor from the inverter and additionally disabling the inverter. This integrated safety helps to ensure that operators have guaranteed levels of protection when performing maintenance on a machine, or for day-to-day needs such as interventions to clear a jam. It greatly simplifies and lowers the costs of system building by eliminating cabling as well as line contactor and switching components.
The inverter can be configured and controlled by PC software with diagnostic functions such as a four-channel oscilloscope, and/or a simple multi-language operator keypad that can be clipped on the front panel.
Nord Gear's Abingdon 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.
More information: www.nord.com/cms/media/documents/bw/bw-E3000_GB.pdf
