Drive conversion keeps 1960s monorail running

Wyko Electro Mechanical Services (EMS) has designed and supplied a brand new drive control system for one of Blackpool Pleasure Beach's oldest and still most popular attractions.

Wyko Electro Mechanical Services (EMS) has designed and supplied a brand new drive control system to help ensure one of Blackpool Pleasure Beach's oldest and still most popular attractions continues to operate well into the future.

Originally purchased from the 1964-65 Worlds Fair in Lausanne, Switzerland where it gave visitors a taste of "transport in the future", the monorail system has since been employed to carry people around the amusement park some 12m up in the air, giving passengers a birds eye view of the activity and rides below.

A series of four trains are powered by a novel system that employs a Ward Leonard AC/DC convertor to power geared DC motors positioned between each of the 12 carriages from a three phase 415V AC supply.

Onboard AC/DC conversion was originally chosen because the DC motors provided more torque from a smaller motor size and were more easily controlled using DC injection to manipulate the field and hence the speed of the motors.

The problem facing BPB engineers was not the technology itself but the cost of continual maintenance on the electrical hardware.

The controller used banks of contactors, timers and rectifiers to direct the power and a manually operated potentiometer with sequenced cams to control the field and hence the speed.

After a recently scheduled major overhaul conducted by Wyko EMS and BPB electrical engineers however, all parties agreed that there must be a drive upgrade solution available using up to date technology that would prove both reliable and cost effective.

Wyko's Electronics Development Director, Victor Harris proposed that the complete DC field control system be replaced on the next train due for a major service with a new state of the art field control system.

This would enable better control of the train's speed, eliminate the obsolete components and enable total integration of the trains safety systems.

To do this, a total rewire of the train's field control system was required.

In the process the main power supply, contactors and control circuits were also resited into a custom built panel in the train's main cab at the front of the train.

This enabled easy access to any ongoing maintenance of the system, unlike the current system, which was under the fabric of the train's body making access very time consuming.

A Sprint Electric PLA applications drive module was selected to co-ordinate the control functions.

Vic Harris states: "The PLA offers a powerful and flexible method of processing analogue and digital signals via easy to use configurable software blocks".

The unit is used to process a speed demand signal and an analogue feedback signal from an electromechanical tachometer on the front of the train, creating an effective PID control loop.

Once the train was actually test running on the track, the various function block parameters were fine tuned on the drive using PL Pilot software on a laptop.

The system provides a controlled startup, continuous speed up climbs and controlled speed down inclines as well as providing a second level of safety redundancy with an electronic speed limiter alongside manually operated e-stops for emergencies.

The Sprint PLA controller is wired to an analogue SLX Sprint Electric DC drive in torque mode that actually supplies the controlling current to the field in the generator, which in turn supplies the drive motors on the carriages with a controlled DC current.

The upgrade work was carried out over a three week period at the end of February and into early March 2004 ready for the start of the summer season.

The new system was tested using a program that was designed to match its performance with the other trains on the track.

Once on the track, fine-tuning took only a few days and the train is now back in full service.

Once its reliability and on going performance have been suitably proved, the upgrade and modification will be carried out on the other three trains.

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