Inverter drives key to wind benefits

Inverter controlled winches are able to accurately and maintain pull forces of up to 40 tonnes in order to test the mechanical behaviour of wind turbine blades up to 70m long. The equipment is installed at NaREC, the New and Renewable Energy Centre at Blyth in Northumberland. We were told on a recent visit that the selection of modules to make up the system began with a competition to choose the most suitable drives. The Control Techniques Unidrive SPs chosen were selected because they could be made to communicate with any other system and, "Could look after themselves." In the Blyth installation, the drives communicate with the supervising Rockwell Automation PLC through a DeviceNet network. The PLC determines loads, positions and sequences. A supervisory SCADA system provides feedback data including loads, cable take up and feedback from the strain gauges. So sophisticated is the system, that once a test cycle has been completed, the National Instruments DIAdem data analysis and report generator can produce a report within 30 seconds. The test facility uses five 11 kW and three 7.5kW drives to control WEG motors to impose winch cable loads from 5 tonnes to 40 tonnes. The blades are de-mounted and re-mounted to allow bend testing from different directions. The adaptor plates take 12 weeks to design, manufacture and install, and are each scrapped after tests are completed for each blade. The drives are fitted with SM application modules. Each drive, running in speed control mode, calculates the movement profile: speed, cable take-up and torque, and communicates with all the other drives, so that they all reach their targets at the same time. The drives also monitor the 4-20mA feedback from the load cells and transmit this information to the PLC. Control Techniques