Drives enable testing of multiple electrical characteristics

When Mixing Solutions Limited, a supplier of industrial mixing machines for world markets, needed a test system that would enable it to accurately determine the current consumption and other electrical characteristics of its products, two AC variable speed drives from Vacon provided a system that promises to be versatile, convenient and cost effective.

At its production site in Newbury, Mixing Solutions, which is a member of the international PSML family of companies, manufactures a range of high-performance industrial mixing machines for applications in the petrochemical, chemical, water treatment and other sectors, a large proportion of the machines being destined for export.

In line with its commitment to ensuring product quality, the company carries out extensive testing on all of its products prior to despatch. In 2010, it decided that it would be useful to include in this testing measurement of the electrical characteristics of the machines using exactly the same supply system - voltage and frequency - as the site where the machine will ultimately be used.

Since supply systems vary considerably around the world, this requirement presented Mixing Solutions with a challenge - how to replicate those supply systems cost effectively for a range of motor sizes with a test rig that could be powered conveniently from the standard 415V 50Hz UK mains supply. For assistance in developing a system, Mixing Solutions contacted T A Boxall & Co Ltd, a company with experience and expertise in variable speed drive systems. After carefully analysing the requirements of the application, the engineers at T A Boxall & Co Ltd proposed a solution based on the use of Vacon NXS-series AC variable speed drives.

For this project, a key feature of these drives is the availability of the Multimotor 7add software option, which allows up to eight types of motor to be controlled from a single drive. When this option is used, the drive stores operating parameter sets that include, for example, full load current and power factor, for all eight of the motors and these parameter sets can be instantly recalled as required by using the drive's auxiliary digital inputs.

NXS drives also have other features that make them an attractive option for this project, including excellent EMC performance without the need for external filters, integrated AC chokes, high starting torque, low noise operation and compact construction, combined with high reliability and competitive pricing.

To meet Mixing Solutions' full range of testing needs, T A Boxall & Co Ltd produced a control panel for the project that incorporates two NXS drives, one rated 18.5kW, the other 75kW. This arrangement means that mixers with motor ratings from 2.2kW up to 75kW can be tested quickly and conveniently. The operation of the drive system is matched to the motor under test simply by using a switch on the panel to select the motor type. This ensures that the correct drive is selected and that the appropriate operating parameters are loaded.

Supply systems of all markets covered

A spokesman says: "The Vacon drives in our new testing panel have made it easy and convenient for us to check the electrical characteristics of our mixers before despatch. With the drives, we can accurately simulate 50Hz and 60Hz three-phase supplies over the voltage range 380V to 500V. This covers the supply systems for all of the markets we operate in but the drives could, if ever we needed them to, easily provide a much wider range of frequencies and voltages."

When the new testing system was first installed at Mixing Solutions, the company envisaged that it would only be used to evaluate new designs and to test mixers destined for especially demanding or unusual applications. The system has, however, been found to be so convenient and easy to operate that it is now used to verify the performance of all mixers produced at the Newbury site.

A spokesman notes: "We can check the normal operating parameters in just a few minutes and, if we need to simulate special operating conditions, we can readily do so by fine tuning the drive set up. This is a very straightforward task using the convenient operator panel that's a standard feature of the NXS drives.

"In our experience, the new testing system is proving to be an exceptionally useful asset and, in line with our corporate policy of continuous improvement, it is allowing us to add an extra level of quality control to our products, without any cost penalty."

Go to www.vacon.com to find out more about the Vacon NXS-series AC variable speed drives with Multimotor 7add software option.