Motors and Drives
Replace, upgrade or retrofit – a designer’s AC drive dilemma
When redesigning a motor-driven application, a vital decision has to be taken: do you replace, upgrade or retrofit the application’s drives? Heikki Kervinen looks at the choices.
W
hen redesigning an industrial application, design engineers are faced with the dilemma of what to do about its AC drives. Should the drives be replaced, upgraded or retrofitted to get the best out
of the application and make it more efficient and capable?
l Replacement: For systems using mechanical controls, such as hydraulic couplings or throttles, there comes a time when the cost of maintaining the old installation is out- weighed by the potential energy savings offered by an AC drive. As well as offering more efficiency, replacing these mechanical controls with new AC drives can bring the very latest motor control methods, communications and user interfaces to the application. Frequently, AC drives and AC induction motors replace
slip-ring motors and direct-on-line (DOL) starting. AC drives can also be used to replace soft-starters, bringing improved process control as well as energy savings and improved reliability. This type of replacement is also attractive because the price differences between small drives and soft-starters are no longer as great as they were.
and sizes, along with invaluable engineering expertise.
l Upgrade: Another fundamental question is whether the AC drive is still providing the correct functionality for the application. Over the past 20 years, AC drives have added a raft of new functions, allowing them to capture data, analyse it using on board software and use the results to control motors via widely used communications protocols such as BACNet. Taking advantage of these functions could be as easy as downloading the latest software or installing some updated hardware. This could
Fig. 1. The power range of ABB industrial drive modules is from 0.55 to 5600kW. The voltage range is from 230 to 690V.
Applications using 12-pulse drives can have these replaced by new active rectifier drives that do not need transformers, which can have losses of around three percent and be difficult to repair. Whenever there is a need to replace an entire AC drive
- from ABB or any other drive manufacturer - or to replace another technology such as mechanical valves or dampers, suppliers like ABB, offer a wide choice of drives of all shapes
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bring many benefits to the process, including faster production times or more data that gives a better, more accurate picture of how the process is performing. An upgrade can have a major impact on the actual process by bringing new levels of efficiency, for example, more accurate positioning
Fig. 2. The SAMI STAR inverter units before the retrofit (above, top) and the new ABB industrial drive modules installed into the SAMI STAR cabinets (above, bottom). New drive modules include capacitors and cable connections that in the previous installation needed separate cabinets.
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