Full implementation of variable speed drives could save industry up to £2.5bn

Written by: Paul Fanning | Published:

The fact that fitting variable speed drives to electric motors can offer significant cost and efficiency savings in industry is hardly news.

However, a new report from Siemens Financial Services illustrates the enormous cost-saving potential in the industrial sector through the use of energy-efficient technologies.

Industrial enterprises across the world could save billions of pounds on their electricity bills by implementing variable speed drives (VSDs) on motors in their production environment. Indeed, the report from Siemens Financial Services has calculated that up to £2.5 billion of energy cost savings could be gained in UK industry with the full implementation of VSDs over the next five years.

Geared motors with integrally-mounted frequency inverters have been available for a long time, of course, but many such units have a limited functional range. Nord Drivesystems, however, equips its SK 200E inverters (below right) with the same wide functional range as the centralized SK 500E series of cabinet-installed inverters. The decentralised frequency inverters not only provide an ample overload capacity of 200%, but also enable users to position the drive precisely.

The relative positions (incremental or endless axes) or absolute values (rotary tables/fixed, repeatable positions) can be controlled with binary values through the SK 200E's inputs and stored within the drive. Alternatively, they can be set via a fieldbus system. Positions can be detected via incremental encoders (an onboard referencing function is included in the inverters' basic equipment), or position values provided by a CANopen absolute encoder may be directly imported.

For lower power drives, typically up to 7.5kW, machine designers can choose their inverter drives either panel- or motor-mounted. By mounting the drive on the motor a decentralised solution is achieved that can save time and costs. The Lenze motec (see above) is a typical example, being available at rated powers 0.37 to 7.5kW either on its own or as a complete variable speed drive package with a geared motor.

Decentralised drives reduce costs for the machine builder in more ways than simply reducing the size of the panel. Power cables can be unscreened which significantly reduces their cost, and where several motors are mounted locally, cable runs can be reduced by looping the power from one inverter to the next. The Lenze motec comes with free software to speed commissioning. In operation a large status LED is visible from considerable distance and a port is available to plug in a diagnostic keypad.

The Lenze motec is able to adapt to individual machine requirements with IP65 enclosure, ambients up to 45ºC without de-rating, and fieldbus options from low-cost AS- to real time EtherCAT and PROFINET. Wall mounting is possible and plug PR-GSS-Auto-warehouse connectors can be provided for faster fitting. Another potential option is Safe Torque Off to Category 4 and Performance Level e.

The C2000 VSD from Softstart UK uses field-oriented control (FOC) as its core technology, taking drive technology to the next level. The C2000 offers speed, torque and position control modes, in a dual rating (normal and heavy-duty) design. Suitable for use with both induction and synchronous motors, the C2000 provides outstanding four-quadrant torque control and torque limit, and smooth motion across the power range.

WEG's new range of CFW500 inverter drives (above left) has been designed to be versatile for many industrial automation applications, including centrifugal and process pumps, fans, compressors and conveyors.

The CFW500 drives are based on modular plug and play design, extremely easy to use and programme. The drive includes a built-in micro-PLC, which can be programmed according to standard protocol IEC 61131-3.

It also comes with pre-programmed macros for a range of applications, for example positioning, timer and acceleration. Users can simply programme the drive using the LCD HMI display, or via a computer through a variety of interfaces (RS232, USB, RS485).

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