AC drives lift efficiency to new heights

. The £960,000 system features a new AC gearless matched drive and motor combination from Control Techniques and Leroy Somer. Ove Arup, consultants for the project, were convinced of the advantages of replacing the existing gearless Ward-Leonard type DC system after seeing a similar AC gearless installation in Ilford. The design, programming and building of the control system was the responsibility of Liftstore, who also built the drive panels and supplied their M6809 advanced dispatch system master control. Liftec installed the panels for the eight lifts, each with a Control Techniques’ 37kW Unidrive LFT AC drive with a sin-cos option module, controlling a Leroy Somer 280M 8-pole asynchronous motor fitted with sin-cos encoder to provide position feedback to the controller that gives an analogue speed reference to each drive. The system gives 2.5m/s running speed, with an improvement in efficiency from around 50% to an estimated 85%, with a saving on running costs too. Jeff Noakes of Liftec commented: “The option to overhaul the existing system and put in new DC drives was considered, but the disadvantages of noise, high maintenance and low efficiency/high energy costs would have remained.” DP Pointers * Replacing the existing DC control system with an AC gearless system has resulted in a 35% efficiency improvement * The new system is also quieter and requires less maintenance * The lift’s control system includes Unidrives from CT and motors from Leroy Somer