Jet engine starter generators on test
03 June 2010
An industrial ac drive is at the heart of a high precision, UK built test rig that is being used to check the performance of Pratt & Whitney PT6 jet engine starter generators
Euravia of Kelbrook, near Colne in Lancashire, has a fully computerised test facility for gas turbine aero engines and auxiliary power units (APUs), including the Pratt & Whitney PT6 turbo prop engine. During one particular test, the PT6 compressor section of the engine is spun 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. APU’s provide the same function whilst the aircraft is on the tarmac.
Euravia was aided in the construction of this rig by online automation distributor Direct-Industrial.com. The latter designed the structural aluminium frame and the electrical and electronic systems, while Euravia designed and manufactured the precision triple mounting heads and the ultra-high-speed mechanical bearing system for the final drive shafts.
Direct-Industrial.com, an official Control Techniques distributor, chose a 15kW Unidrive SP ac drive for the central task of testing the generator function. Rig control is via an HMI and a PLC running a bespoke test programme written by Direct-Industrial.com. The PLC communicates with the Unidrive SP via the latter’s integral Modbus function, enabling rapid and extremely precise responses to acceleration and deceleration commands under conditions of high torque and speed.
The rig comprises three sections. One tests the ability of the starter to run up to speed against defined loads, another - driven by the Unidrive SP - carries out a series of tests at speeds of 6,700, 7,800, 12,000 and 14,000rpm, while a third section tests the starting torque. Shaft torque, temperature, voltage, current, impedance and radial vibration are all recorded during the test sequences and these readings are transmitted to the PLC, where test results are formulated and automatically compared against preset parameters.
The Unidrive SP is a flexible drive and it proved ideal for this application, not just for its easy interfacing to the PLC but also for its dynamic and accurate response to the test system commands. Euravia is reported to be delighted with the rig, which is now in daily use testing starter generators for a range of PT6 and PT6A aircraft engines.
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