Frequency inverters help reduce motor size needed

Edited by the Engineeringtalk editorial team Feb 4, 2008

Nord Gear frequency inverters can allow low-cost AC motor equipment to be used in place of much more expensive motion controller and servomotor based automation.

Compact frequency inverters from Nord Gear UK can be adapted to suit specific applications, from simple speed control of AC motors, to complex movement automation.

A 200% overload capability will in many cases allow a smaller inverter drive to be selected, cutting as much as 10% off typical equipment costs.

Motor torques of 200% nominal level can even be delivered at zero speed.

This level of performance and precision control can, in many instances, allow low-cost AC motor equipment to be used in place of much more expensive motion controller and servomotor based automation.

The Nordac SK500 inverter family spans power output ratings from 0.25 to 7.5kW, covering a large range of common industrial applications.

It 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.

Nordac SK500 family inverters can store up to four complete programs, allowing systems to 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 and factory networking.

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.

The generous overload capability of the Nordac SK500 family of inverters is particularly useful for 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.

This can be readily exploited by system builders to save costs when automating processes that might require high starting torques or be exposed to occasional high-shock loads.

A built-in "safety stop" function can be used to implement either category 3 (single-channel stop) or category 4 (dual channel stop).

The feature can be used to isolate the motor from the frequency inverter, or to isolate the motor from the inverter and disable the inverter.

This integrated safety can be used to ensure that the operators have guaranteed levels of protection when performing maintenance on a machine, or for day to day needs such as when intervening to clear a jam.

It greatly simplifies and lowers the costs of system building by eliminating cabling plus line contactor and switching components.

Configuration and control of the inverter can be achieved by means of PC software that has diagnostic functions such as a four-channel oscilloscope and/or a simple multilanguage operator keypad that can be clipped on the front panel.