Drives quieten fans in mobile operating theatres

A Siemens Automation and Drives product story

Edited by the Engineeringtalk editorial team Jan 29, 2002

State-of-the-art, mobile operating theatres produced by the Cambridge based military suppliers, Marshall SV are now being fitted with variable speed drives to deliver reduced noise and vibration

State-of-the-art, mobile operating theatres are now being fitted with the Siemens MicroMaster 420 range of variable speed drives to deliver reduced noise levels and vibration.

Used at crisis locations throughout the world, the units are produced by the Cambridge based military suppliers, Marshall SV.

This new concept in operating theatres moves field surgery permanently out of tents.

MASH may have been entertaining television but the facilities depicted represented the medical norm over half a century ago.

The Marshall SV design for a Modular Transportable Surgical Facility (MTSF), was selected by the United Kingdom Ministry of Defence following an intense international competition.

The design is based on high specification ISO container sized modules.

Each MTSF system consists of four fully equipped modules to provide surgery, intensive care, plant and interconnection.

Four MTSF systems are now complete and will be going into service with the UK Army during 2002.

MTSF has also been supplied for use by Aid Agencies for civilian relief in the event of major disaster.

Transport of MTSF by road, rail, sea and air and rapid deployment anywhere around the world means the availability of life saving equipment when and where needed.

The need for modules to fit into the hold of a Lockheed C130 Hercules and the decision to make the MTSF design NHS compliant placed stringent limits on size and the performance of plant.

Telescopically expanding sides in the surgery and intensive care modules solved space limitations, but the noise levels of the fans fitted to the electricity generators proved unacceptable.

Although medical staff and patients were not affected by this problem, the need for operators to wear earmuffs in deserts, and other high temperature locations, was considered impractical and the search was on for a more user-friendly approach.

Siemens solution to the problem was to fit an inverter, so that the fan speed could be varied in direct relationship to the coolant temperature of the generator.

A MicroMaster 420 was fitted to each unit and the speed controlled by an analogue input from a temperature probe on each diesel set.

The MicroMaster 420 is produced in three sizes to cover the range from 120W to 11kW and is designed to operate in extremely hostile environments with humidity levels of up to 95% and temperatures between -10�C and +50�C.

The solution has the advantage that, wherever the theatre is located, fans are run at the lowest speed that can keep the generator's engine cool.

Noise pollution is kept to a minimum and the use of a variable speed drive reduces wear on the fan bearings and minimises energy use.

Launched only a year ago, the MicroMaster 420 is built at Congleton, in Cheshire, and complies with all European and international standards.

The wide operating voltage range ensures that 420 units remain unaffected by supply voltage fluctuations.

The design also includes a Profibus interface that enables MicroMaster to communicate with all types of field devices and the inclusion of structured, numerically grouped parameter sets simplifies start-up.

MicroMaster 420 has voltage and frequency programmable characteristics and can be used with both synchronous and asynchronous motors.

However, the flying re-start function is potentially the most useful as this allows motors to be run up quickly after a supply failure.