Variable Speed Drives Keep Up the Pressure in Swiss Elevators

The Challenge

Bucher is famous for its innovations, including their electronically controlled LRV valve that is insensitive to changes in pressure and temperature, and brought significant energy savings to elevator production, as well as shorter travel times and virtually eliminated creep-to-floor. Striving for further system improvements, Bucher was seeking a way to improve elevator control.

The Solution

Having carried out considerable research, Bucher decided to use AC drives from Control Techniques and created BERIPAC™, which uses a hydraulic counterweight with fourquadrant pump. It has direct-to floor operation and has eliminated the need for an oil cooler. The company chose the Unidrive from Control Techniques for pump motor control as it is “the one which we consider has the best combination of accuracy and reliability – plus outstanding international support”, said Bucher Hydraulics Product Manager, Mr Grab.

The powerful Bucher controller receives multiple feedback signals, such as temperature, oil pressure and car position, from an absolute encoder and, on receiving a request, calculates the required riding curve. As the lift car comes down the shaft, its potential energy is released in the form of oil pressure that is stored in a hydraulic accumulator. On rising in the shaft, this energy is released in a controlled way via the pump to the pulling cylinder to minimise the additional electrical energy that is required.

The Benefits

The compact, two-part elevator control cabinet can be sited almost anywhere and encompasses the elevator controller and Unidrive, as well as the hydraulic cabinet with emergency controls and 45-litre fluid tank.