Driven away

Wherever industry needs to optimise cost, productivity or functionality, mechanical parts are being replaced by software-supported drives. Mark Venables investigates.


Greater flexibility continues to be demanded from industrial drives within the variety of sectors and applications in which they operate. To meet these demands, drives must usually satisfy one of three requirements — to reduce costs, to increase productivity or to increase functionality. Nowadays it is not always the drives themselves that provide these abilities — often they are delivered through software that is either embedded or supplied as a standalone package.



Cost reduction

A good example of reducing costs comes from the entertainment sector in an upgrade to the heating and ventilation (HVAC) system at the Birmingham Hippodrome theatre, where costs are being cut through the use of variable speed drives. The drives, from ABB, are slashing the energy consumed by motors for HVAC duties by more than a quarter.

The 29 ABB HVAC drives range from 2.2 to 30kW and control motors on the pumps that move hot and chilled water around the building. The motors have been using 25-30 per cent less electricity with the drives, while the cost of running the fans that keep air flowing through the ventilation system has been cut by 28-30 per cent, according to facilities manager Mike Croke.

The project started when the Hippodrome called in an assessor from the Carbon Trust to survey the building’s energy efficiency. ‘This was one of the big projects that the assessor identified,’ Croke said. ‘He also pointed out that we could get an interest-free loan towards the cost from the Carbon Trust, which was obviously appealing to us.’

Armed with a £60,000 loan, the Hippodrome upgraded to the HVAC system, through heating specialist ADT. As well as installing the variable speed drives ADT upgraded the theatre’s building management system to use BACnet, which is a communications standard specially developed for building services — the protocol offers ‘plug and play’ integration of devices, without the need to pay a licence fee. ‘We wanted BACnet for several reasons,’ said Mike Cassell, field line manager for ADT. ‘Ease of installation was the main thing but BACnet also offers more data, better control and makes it easier to monitor the drives from a single point.’

BACnet is also helpful for end-users, according to Croke: ‘It’s not something we’d use every day but it gives us more information about how each drive is performing and helps us monitor the performance of the overall plant.’

Before the upgrade, hot and chilled water was pumped around the theatre by a system of duty and standby pumps, so that one pump in each pair ran at full speed while the other stood idle. The new drives enable both pumps in each pair to share the load by running at around 65 per cent capacity. Every pump operates closer to optimum efficiency, reducing the electrical demand for each job by 25-35 per cent.



Productivity increase

For the printing industry, increasing productivity is the key and this is where an AC drive system from Allen-Bradley can help. An electronic line shaft using Allen-Bradley PowerFlex 700S AC drives from Rockwell Automation can reduce press downtime, allowing the industry to maximise automation investments. The precise positioning capabilities of the drive enable it to replace outdated mechanical line shafts and gearboxes in printing, web handling and other tension control applications.

The electronic line shaft system offers printers a convenient method of maintaining speed and registration control of presses. Users can enjoy the benefits of shaftless drive control, including increased flexibility, improved power transmission and reduced downtime.

Gerry Niebler, print marketing manager at Rockwell Automation, said: ‘Printers who are looking to upgrade their control system will benefit from the flexibility and performance of the drive in an electronic line shaft configuration. In addition to eliminating the costs of spare parts, the system provides precise positioning and synchronisation for increased productivity.’

With the electronic line shaft capability, users can reduce the complexity of their system by eliminating rotating components when transmitting power from line shaft motors to the press itself.

Drive-to-drive synchronisation may be achieved with SynchLink — a high-speed, drive-to-drive fibre optic data link that transmits drive and application information for multiple drive synchronisation. Designed to improve accuracy in printing, SynchLink eases the transmission of speed and position reference to help ensure all drives are tightly synchronised, thereby allowing registration and compensation moves to be performed electronically.

When it comes to increased functionality, industrial ironing machines have benefited from drive technology from Lenze, used to provide accurate variable speed control for the Electrolux range. The stepper motor drive (SMD) units range from 15 to 22kW for the larger machines and were chosen because they were easy to set up, cost-effective and compact, fitting inside the existing machine design envelope.

The range of AC drives is designed to bring inverter drive functionality to a wider range of simple motor control applications (often replacing mechanical speed control such as friction-based clutches, brakes, 2x speed gearboxes, baffles and dampers).

The ironing machines retain a manual speed control via a hand-operated knob (a potentio-meter wired directly to the SMD drive), which can control the rotation speed of the cylinder. Advanced models employ an automatic function where the machine senses moisture levels and adjusts the feed rate accordingly.

The signal is fed back to the drive and the fine speed adjustment is made according to preset parameters. Consistency of speed and pressure is essential for good results, as anyone who has successfully ironed a shirt will attest. The process relies on the company’s experience and the accuracy of the SMD drive unit to achieve smooth, precise drum rotation at fine speed increments. The result is dry linen with perfect finishing.

The items being ironed are being pressed as well as steamed, hence the torque loads are high and variable; and, with only limited space for the drive, the SMD’s compact size was a bonus for the engineers. In-line filters were supplied, ensuring that electromagnetic compatibility levels are met, whatever markets the machine is intended for.

Another major benefit to Electrolux is the innovative electronic programmable module memory chip, a 1cm cube that can be programmed and copied independently. This plugs directly into the front of the SMD drives’ outer casing, which allows each ironing machine to be commissioned without power being supplied.