As the legislation surrounding the efficiency of electric motors continues to tighten, the volume of variable speed drives (VSDs) in service increases. Often specified by the motor manufacturer as part of the original installation – or retrofitted to improve efficiency – the drive contains both hardware and software that is designed to work with a motor in a specific application. So, what happens if the drive ceases to operate? Brian Park, Regional Sales Manager for Scotland at Sulzer, looks at the advancing technology and the maintenance processes that need to keep pace.
Posts Tagged ‘Inverter’
The MW500 frequency inverter with decentralised design has been developed for space-saving solutions, such as directly motor mounted or adjacent to the motor on the wall. As a result, the need for lengthy cables and switch cabinets is eliminated. MW500 is robust with an IP66 protection rating. It can withstand high overloading of 150% for 60 seconds every 10 minutes, and operate in temperatures up to 40°C (wall installation) and 50°C (motor installation). With increased ruggedness compared to alternative technologies, it provides reliable operation over a long service life. The inverter is designed to operate asynchronous motors in the power range 0.75 to 7.5 kW, and is offered as three variants for a mains voltage of 380 to 400V (A: 1.1 to 1.5 kW, B: 2.2 – 4 kW and C: 5.5 – 7.5 kW), and for 200 to 240V, as variant A (0.75 to 1.1 kW). It is ideal for many pump applications.
Mitsubishi Electric has added dust and splash-proof versions with an IP55 protection rating to its FR-A800 series of frequency inverters. Specially designed for harsh environments and tailored to the requirements of pumps, the drives are highly robust and ideally suited for use in industrial and commercial building automation systems as well as in heating, ventilation and air-conditioning systems. The new FR-A846 series with an IP55 protection rating represents Mitsubishi Electric’s latest drive technology in the output range from 400 watts up to 160 kW. The drive’s EMC filter built in as standard ensures full compliance with the EMC Directive (EN 61800-3, 1st environment, category C2) while its DC reactor – also built in as standard – ensures full compliance with IEC 61000-3-12 for reducing and limiting harmonic currents so that separate certification is not required. The FR-A846 also has a built-in main switch version with locking option.
Plant and maintenance engineers often seem to have an intuitive nose for trouble, so are able to predict pending problems with machinery and take pre-emptive action to prevent them. It is not the result of magical powers, rather of long experience with plant and machinery. Bill Bertram of motor maker Marathon Electric explains how different motor sounds can be interpretedÖ: “If you walk around a piece of plant that is running, you will hear it making a noise. If you listen carefully you will be able to pick out individual elements within the overall sound. For instance, you may be able to hear a fan whirring, a pump thumping and a conveyor rumbling.”