Euravia bolsters test rig with AC drives

14 May 2010

Euravia of Kelbrook, near Colne in Lancashire utilises a computerised test facility for gas turbine aero engines and auxiliary power units (APUs). The company recently turned to Control Techniques for a variable speed AC drives for use in the test rig.

Aero test rig at Euravia
Aero test rig at Euravia

One of the range of tests concerns the performance of the compact, powerful engine starter generators. 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 craft’s electrical system, such as fans, pumps and lights. APUs provide the same function whilst the craft is on the tarmac.

Euravia called in online automation distributor to look at the requirements for a test rig to undertake a series of tests to check on refurbished starter-generator performance. and Euravia pooled technical resources, with Direct-Industrial designing the structural aluminium frame and the electrical and electronic system. Euravia designed and manufactured the precision triple mounting heads and the extremely high-speed mechanical bearing system for final drive shafts., an official distributor of AC and DC drives for Control Techniques, 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 incorporated into a PLC. It was found that the Unidrive SP and the Pixys proved to be a good combination, communication being via the standard ModBus built into the drive. The drive responds to constant acceleration and deceleration commands in high torque and speed situations very rapidly and precisely 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; 6,700rpm, 7,800rpm, 12,000rpm and 14,000rpm; with parameters fed back to the PLC. The final test involves the checking of starting torque, with 800 amps 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.

John Lenehan, managing director of, described the Unidrive SP as “very flexible” and said its instant compatibility with the PLC and dynamic and accurate response suited to the application.

The finished rig 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 wide range of models with a power range from 600 to 1940 shaft HP.

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