Imperial College wind turbine upgrade turns on ac precision 15 February 2013

Imperial College London's Department of Aeronautics is reporting a rapid response from Dynamotive and Control Techniques on an urgent upgrade for its 3ft x 3ft, 150 ft/sec wind tunnel.

This project arose because the existing dc motor and controller failed during a time-limited testing project being carried out by one of its PhD students.

The university says that it chose Dynamotive and Control Techniques following their success on the high profile Honda Wind Tunnel.

This time, the department specified a fast turnaround ac motor solution - ac being preferred because of its reduced maintenance – with a PLC controller for sequencing, an HMI and a Control Techniques ac variable speed drive.

The drive chosen was a 37kW Unidrive SP, fitted with an SM Ethernet plug-in module to enable communications with the Proface touch screen colour HMI supplied and programmed by Dynamotive.

Temperature monitoring of the motor is fed back via the PLC. A multi-port network switch enables the ac drive, the PLC, the HMI and the university's remote control PC to share the Ethernet network.

The 37kW motor was a special order through Emerson Control Techniques. It is a six-pole unit fitted with a 1,024 ppr TTL optical encoder that feeds back to the drive for closed-loop Vector speed control, delivering accurate low-speed speed control for the wind tunnel's driven fan.

In remote control mode, the university closes the loop externally, taking into account differential pressure feedback from the tunnel's test section area. The researcher then issues a corrected rotational speed setpoint via the ac drive to achieve the desired wind speed.

Brian Tinham

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