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Euravia is using a variable-speed AC drive from Control Techniques in a PT6 jet-engine starter generator.

Euravia has a fully computerised test facility for gas-turbine aero engines and auxiliary power units (APUs), including the testing of the PT6, a reliable turboprop aircraft engine.

One of the tests concerns the performance of the compact yet powerful engine-starter generator.

Its function is to spin up the compressor section of the engine until it reaches the required RPM and the engine is self-sustaining.

At this point, it becomes a generator to maintain the aircraft’s electrical system – fans, pumps, lights and other electrical equipment.

APUs provide the same function while the aircraft is on the tarmac.

Euravia called in online automation distributor Direct-Industrial.com to look at the requirements for a test rig to undertake a series of tests to check on refurbished starter-generator performance.

Direct-Industrial.com and Euravia pooled technical resources, with Direct-Industrial.com designing the structural aluminium frame and the electrical and electronic system.

Euravia designed and manufactured the precision triple-mounting heads and the high-speed mechanical bearing system for the final drive shafts.

Direct-Industrial.com, an official distributor of AC and DC drives for Control Techniques and a long-time user, chose a 15kW Unidrive SP (solutions platform) AC drive for the central task of testing the generator function.

The control of the rig is via an HMI with a bespoke test programme written by Direct-Industrial.com incorporated into a PLC.

It was found that the Unidrive SP and the Pixys proved to be the ideal combination, communication being via the standard Modbus built into the drive.

The drive rapidly responds to constant acceleration and deceleration commands in high torque and speed situations, with no overshoot and absolute accuracy.

The rig comprises three sections for three series of tests.

On the left, the section tests the ability of the starter to run up to starter speed against defined loads.

The central section, driven by the Unidrive SP AC drive, carries out a series of tests at a series of defined speeds; 6,700, 7,800, 12,000 and 14,000rpm; with parameters fed back to the PLC.

The final test involves the checking of starting torque, with 800A being applied to the starter, which has a locked shaft – in one test, for instance, looking for a torque level of 20.3Nm (15ft lb).

Readings of shaft torque, temperature, voltage, current, impedance and radial vibration are all recorded during the test sequences and fed back to the PLC, where test results are formulated and automatically compared against preset parameters.

The Unidrive SP AC variable-speed drive-range spans 0.75kW right up to 1.9MW.

Unidrive SP is the world’s most advanced ’solutions platform’ AC drive, configurable into five operating modes – open and closed-loop, vector, servo and regenerating modes – connectivity to most industry-standard networks and accepting most position-feedback protocols.

Euravia is delighted with the finished rig, which is now in daily use testing starter generators for a range of PT6 and PT6A aircraft engines.

The first PT6 was introduced into commercial service in 1964 by Pratt and Whitney Canada, and is still in production today.

It is produced in a range of models with a power range from 600 to 1940 shaft HP.

Euravia is a modern, independent aviation company offering high quality, cost-effective repair-and-overhaul services for a wide range of gas turbines, including Pratt and Whitney PT6 engines, Honeywell, Hamilton Sundstrand and TRW APUs, as well as various engine and airframe components and accessories.

The company has three facilities in Kelbrook that cater for all aeronautical engine maintenance, repair and overhaul; test and component rework requirements, including fully computerised dynamic balancing.

Euravia’s JAR-145-approved PT6 programme offers the highest quality repair, hot-section inspection, overhaul and test services in accordance with OEM specifications.

Control Techniques

Control Techniques, an Emerson Industrial Automation company, is a world leader in the design, production and marketing of electronic variable speed drives for the control of electric motors. Our strategy is to concentrate on delivering drives and servo products that enhance the productivity of our customers’ machines and processes.

We operate through a global network of drive and application centres that both distribute product and add value by building our drive products into custom designed systems and by offering the highest levels of customer service.

Our Control Techniques drive centres also provide us with invaluable feedback and market intelligence so that we can further improve our products and service. This customer focused strategy will enable us to continue to grow profitably.

Our competitive edge is based on our unique focus on drives, our strength in research and development, our investment low-cost manufacturing and an effective worldwide marketing strategy.

Emerson Industrial Automation, a business of Emerson, is a global technology provider that enables productivity, efficiency and quality gains for customers across a spectrum of industries. Our products include alternators, electric motors and drives, electrical distribution devices and mechanical power transmission, fluid automation and ultrasonic joining solutions. Visit our website for more details.

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