APPLICATION BULLETIN - AUGUST 1999 | BACK TO INDEX  

PDL and Schindler Lifts - A Winning Team at Eden Park

Eden Park's new ASB Bank Stand was officially opened in July this year with four multi-level elevators equipped with PDL Electronics AC motor controllers and VYSTA, PDL's outstanding new visual programming platform.

The new stand is part of a multi-million dollar development designed to make the facilities at the famous Auckland, New Zealand rugby and cricket ground world-class and features a number of corporate boxes and restaurant areas.

Schindler Lifts NZ Ltd, one of the country's leading elevator and escalator suppliers and part of the Swiss Schindler Group (one of the largest elevator-escalator manufacturers in the world), produced and supplied the elevators for the Eden Park project. The company use PDL AC motor controllers in New Zealand and Australia.

Schindler Lifts' technical engineer, John Locke explains, "We have had a long-standing preference for PDL motor controllers for a number of reasons. As a local manufacturer PDL offers us customised solutions and instant application engineering assistance. VYSTA programming sets PDL AC motor controllers apart from other AC motor controller manufacturers. It allows much more scope for advanced programming ­ similar to a PLC ­ and the flexibility that goes with it."

One of the elevators is a custom engineered through-entry 3000kg traction Goods/Passenger elevator which serves five stops at a speed of 1m/s with a total travel of 21 metres. The other three are Schindler 16 person (1150kg) traction passenger elevators which serve four stops at a speed of 1 m/s with a total travel of 14.8m.

The Goods/Passenger elevator is equipped with an Ultradrive Elite 90 Amp AC motor controller and the three passenger elevators each have Microdrive Elite 46 Amp motor controllers ­ all of which have been configured with VYSTA. The drive's job is to manage the information sent to it by the Schindler control system. It must adhere accurately and reliably to any order it is given and control the motor accordingly.

The Elite Series is the latest in a line of world-leading AC motor controllers developed by PDL and can be extensively customised quickly and easily via the new VYSTA platform. VYSTA uses a graphical function block editor where process control function blocks can be assembled and interconnected to build customised applications. Once a control system is configured within VYSTA, the program is then compiled and downloaded to the controller via an RS232 serial port.

PDL Electronics Application Engineering Manager, Alan Tims says, "Elevators provide a number of unique challenges. Engineers judge them on the smoothness of their acceleration and deceleration, and on their ability to position as close as physically possible (within millimetres) to floor level."

In the early 1990's the use of AC variable speed drives was relatively new within the elevator industry and many basic (1-2.5 metre/second) elevators were equipped with either variable voltage AC drives Direct On-Line (DOL) motors or simple geared DC motors.

Schindler's Wellington-based National Modernisation Manager, John Mardell, knew there were definite advantages in using AC motors with variable frequency drives - they run cooler and there is less maintenance - but the AC motor controller the company was using at the time had a number of limitations and was not suitable for meeting the level of specification the new upgrades required.

Mardell wanted a better, more efficient and more cost-effective way to control the motors in the lifts he was specifying. PDL proved it could successfully address the issues and quickly and efficiently 'create' a unique Schindler application.

At the heart of PDL's first solution, in 1993, was special software developed for a Microdrive-3 (UD3) to;

a) match elevator controller I/O control logic, and

b) provide dynamic, smooth and controlled elevator car travel.

Key features were its binary, multispeed I/O configuration, separate acceleration and deceleration break points, the modification of the S-curve at various speeds and the inclusion of some special default settings.

The drive software also manages the acceleration and deceleration so that ascents and descents are as smooth as is practically possible within the shortest time.

The first PDL UD3-equipped elevator was installed at the Waikato University in 1993 and though not primarily designed with hoisting applications in mind, the open-loop V/Hz drive proved particularly successful in this application - its superior motor control (it has a slip compensation feature which operates equally well in motoring and regeneration mode) providing the desired level of open loop positioning accuracy. Schindler Lifts installed 41 more before upgrading to a Microvector controller (the closed loop vector version of the UD3) in 1994.

The PDL Microvector offered even better dynamic performance (particularly at low speed) and more accurate final positioning. The company used it until upgrading again to the current technologically advanced PDL Microdrive Elite/Ultradrive Elite-VYSTA package. To date more than 100 PDL AC motor controller solutions have been installed in Schindler Lifts applications - supplied complete with dynamic brake modules and dynamic brake resistors.

For the VYSTA package, Schindler Lifts requested four different speed profiles (including S curves) plus one hand speed profile because each action - acceleration, deceleration, acceleration from rest to the acceleration rate then from the acceleration rate to the fixed rate etc. - has its own special requirements.

The Elite Series motor controller and VYSTA combination has enhanced cost and time efficiencies well beyond past PDL solutions. This is because the original PDL software was embedded at assembler level, posing a limit - in terms of time, money and convenience - to what could be changed, and any software modifications were supplied via EPROM. Since VYSTA is configured at the application level, changes can be made by a PDL Electronics application engineer (rather than an R&D engineer) - or if desired, a Schindler Lifts engineer.

Schindler now has the software and PDL application engineers can e-mail upgrades if and when they are required. Convenience like this means that Schindler Lifts can now order motor controllers 'off-the-shelf' and configure them on-site - which is how the solution was delivered for the Eden Park project.

The move to the Elite Series of motor controllers also allowed the PDL engineers to add even more features - including multiple S-curves, a special torque mode and the display of elevator car speed in linear units. VYSTA has pushed the boundaries of stand-alone VSD applications, with an ever-increasing range of VYSTA installations operating in diverse industries throughout the world.