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PR King & Sons


Mosman, NSW

Family-owned PR King & Sons specialises in ‘Inclinators’, or inclined lifts designed to transport people up steep inclines. The key to the Inclinator’s success – which was custom-built by PR King in its Marrickville factory – is the efficiency of the incorporated variable speed drive which synchronises the break with the power turning off, eliminating rollback.

For the Mosman project’s passenger lift, which required six stops on almost inaccessible terrain with an incline changing from 36 to 45 degrees, the PR King engineers, together with Schneider Electric, introduced an entirely new solution – a closed-loop feedback on the drive vector control that gives full torque performance of the motor at zero speed, without mechanical break and independent of load.

Behind this solution was Gardner Automation, together with the Schneider Electric variable speed drive, the Alitvar 71 (ATV 71). An encoder fits on the back of the motor under the Inclinator’s cage and is used for two different functions: one for positioning and the other to give full flux vector control on the motor, which allows torque at zero speed. This method has been so successful that PR King has made it a standard for all its multi-level installations.

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