Gearless lift replacement is quiet revolution

A major refurbishment of a Birmingham office block has one feature that points the way to a quiet revolution that is taking place in the lift market.

A major refurbishment of a Birmingham office block has one feature that points the way to a quiet revolution that is taking place in the lift market.

The 12-floor Axis Building, perhaps better known as Stanier House, features the first eight-car AC gearless control systems installed by independent UK-based company, Liftec.

The GBP 960,000 system features a new AC gearless matched drive/motor combination from sister companies Control Techniques and Leroy Somer, giving major user advantages including quiet, smooth operation, low maintenance and a dramatic 35% improvement in efficiency.

Ove Arup, consultant for the project, became convinced of the advantages of replacing the existing gearless Ward-Leonard type DC system after seeing a similar AC gearless installation in Ilford - and the cost saving was a further important consideration.

The design, programming and building of the control system was the responsibility of Liftstore, which built the drive panels and supplied its M6809 ADS (advanced dispatch system) master control.

Liftec installed the panels for the eight lifts, each with a Control Techniques 37kW Unidrive LFT AC drive with a sin-cos option module, controlling a Leroy Somer 280M eight-pole asynchronous X8 lengthened motor fitted with sin-cos encoder to provide position feedback to the controller that provides an analogue speed reference to each drive.

"The option to overhaul the existing system and put in new DC drives was considered", says Liftec's Jeff Noakes, "but the disadvantages of noise, high maintenance and low efficiency/high energy costs would have remained.

We believe that AC is the future and the combination of better performance and reduced running costs was a very persuasive argument".

The new system gives 2.5m/s running speed, with an improvement in efficiency from around 50% to an estimated 85%, giving a saving in running costs.

Perhaps more significant over the lifetime of the system is the dramatic reduction in maintenance - "and the user isn't tied into expensive one specialist supplier service contracts on the drives and motors", adds Jeff Noakes.

"It's all standard kit".

Control Techniques Unidrive LFT is specially designed for the lift market.

Offering open loop, closed loop or servo operation via simple parameter selection, the drive is packed with features as standard, including an onboard PLC option for speed profile generation and call handling control, a braking unit on-board, an encoder feedback module and high switching frequency for an ultrasmooth ride.

As part of the product offering from Control Techniques, the new Unidrive SP AC drive up to 30kW is available with sin-cos encoder input and 48V DC input as standard which can be used in situations such as power loss.

With Unidrive SP the lift can be safely moved to the nearest floor in the event of power failure.

The Leroy Somer eight-pole asynchronous motor has a full load torque of 1590Nm and a maximum acceleration torque of 2650Nm, with a maximum suspended load capacity of 8.5t.

Each motor has a nonstandard sheave of 700mm to give increased torque.

The brakes and sheaves are demountable to facilitate ease of handling and to reduce weight.

The M6809 controller from Liftstore is a versatile, robust generic controller that is field-proven and very reliable.

It has an easy-to-use interface with clear LCD, data logger with real-time recording of 100 different types of events and floor position, car direction, door status and lift status graphical displays.

A hand-winding system was fitted for emergencies.

Users of the building have noticed an improvement in call handling and response times and have commented on the quiet operation of the lifts.

"This was the first AC gearless job we have done in the UK, and it went like clockwork, thanks to the support from Liftstore and Control Techniques", says Noakes.

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