Eiffel Tower North Pillar: Automation of a Sloping Lift

For over a century now, a trip to the top of the Eiffel Tower In Paris is considered to be a "must" in the tourist world.

With 3 lifts going to the first 2 levels and a further 2 which go right to the top, around 5.5 million visitors a year ascend the 300 m in a matter of minutes. The drive and control equipment for the electric lift which climbs the structure of the North pillar has been refurbished.

The "Societe Nouvelle de la Tour Eiffel" (Eiffel Tower management company) has chosen Groupe Schneider to perform this renovation work. Spie Trindel is in charge of the electrical installation work and replacing the traction motor and Spie Automation the supervision. Telemecanique has been responsible for the motor control and monitoring system using Rectivar 4 variable speed drives and TSX 7 PLCs, connected via a dual Ethway network to the supervision system.

The Lift

Built by Schneider Creusot in 1965, the North pillar lift is similar as are its equivalents on the other pillars, to a funicular railway with an incline which varies between 54° and 78°. In fact, contrary to traditional lifts, it does not move in an enclosed shaft along straight guides, but runs on standard rails. A double carriage is mounted on the undercarriage. Together these form a variable geometry mechanism whose seating is supported by hydraulic jacks, whatever the angle of the track. The lift is moved by a winch which in turn is activated by a 355 kW separate field excitation d.c. motor. Two 2.85 m diameter Koeps pulleys, coupled to the motor by a differential reduction gear, drive 4 cables by friction. The load of the double carriage plus half the maximum playload are balanced by a 43 T counterweight. This is mounted on a trolley with a 4 ratio block and pulley system, which runs on a parallel track.

The mechanism has 3 different brake systems:

• security brakes : these are pneumatically controlled band brakes, mounted on each driving pulley; they are used for stopping on a fault,

• operational brakes : on the fast shaft, at the motor output; they consist of 2 clamps, one of which is regulated to maintain a braking deceleration of 1 m/s², while the second is an on-off brake, and used as a parking brake,

• emergency brakes : on the undercarriage ; they are activated by an overspeed of > 3.5 m/s or by the cable snapping ; they are claws which lock in the rack rail; the stop is damped by 4 oil coated hydraulic jacks.

The lift serves the first and second levels of the Tower.

Objectives

• Safety and availability, hence redundancy

• Lifts standard

Solution

All equipment is duplicated, from the MV/LV transformer station through to the motor:

• two 20 kV/600 V, 630 kVA power transformers,

• two 380 V/220 V, 100 kVA control transformers,

• two sets of H5/H7 harmonic filters,

• two 1200 A variable speed drives,

• two control PLCs working in redundant configuration,

• all safety devices such as those to protect against overtravel, overspeed and slowdown control, etc., are also controlled by a hard­wired logic sequence, in accordance with the Lift Standard.

Operating modes

• Automatic: the machine is directly controlled by a lift operator in the carriage, who can only control the up/down and emergency stop controls. The speed is set at 2.8 m/s.

• Manual: the machine is controlled from the control panel at ground level, using the same controls as above. The speed can be adjusted from 0 to 2.8 m/s using a potentiometer. This operating mode is used daily when the lift is first started up, performing a return journey to run in the mechanism.

In these two operating modes, the lift systematically and automatically stops at the first level.

• Manual inspection: the machine is controlled from the control panel; the speed is limited to 0.7 m/s and is controlled manually. This is the maintenance, repair or test operating mode. It does not systematically stop at the first level. In these 3 operating modes, acceleration and deceleration is automatically controlled according to the speed.

• Breakdown mode: this is only used in the event of the mains supply or the Eiffel Tower back-up supply failing, or if the driving motor fails. It enables the carriage to be brought back to a level by releasing and manually operating the service brakes.

Either of two redundant Rectivar 84 1200 A digital variable speed drives can control the motor. Either of the two TSX 87-40 PLCs can also generate the signal for either of the speed drives, depending on the selected operating mode and the carriage position / speed feedback. This data is provided by the 4 encoder / tachometer pairs on the motor and the driving or deflection pulleys, and by magnetic switches on the track.

Communication between the carriage and the ground is performed by 2 types of connection with the carriage, either by inductive loop or by carrier current (Satec system) on one of the supply phases. The 2 PLCs are linked by a dual Ethway network to which a supervision system, developed by Spie Automation, is connected. This enables images to be shown, faults to be displayed, data logging, assistance with control and trouble-shooting. A further connection to the Building Management system will relay this supervision data to the Central Safety Station.

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