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Rarity of rare earths prompts a renaissance in motor design

20 March 2013

China’s move to corner the market for rare-earth minerals has prompted manufacturers of low voltage industrial motors to adopt alternative technologies.

According to a soon-to-be-published report from IHS IMS Research, the global market for industrial IE4 Super Premium Efficiency low voltage motors will rise 153 percent above its 2012 level to reach an estimated $418.2m by the end of 2015. Emerging lower-cost alternatives to traditional permanent magnet synchronous motors (PMSMs) that achieve IE4 levels of efficiency have added momentum to this niche market.

IE4 low-voltage motors based on the traditional ac induction squirrel-cage design (PMSMs) have been heavily dependent on rare earth minerals (REMs) like neodymium and dysprosium, which are needed for the high-powered magnets that generate motor efficiencies above IE3 and NEMA Premium.

PMSM motor manufacturers were badly hit by REM export caps imposed by China, the world’s leading producer and processor of these minerals, which caused neo-magnet prices to skyrocket in 2011. Prices did stabilise mid-2012, but they remain high and represent a cost concern that motor manufacturers must inevitably pass on to their customers.

IHS analyst Mark Meza says that, like the samarium cobalt (SmCo) magnet sourcing scarcity of the 1980s - which hastened the development and introduction of neodymium magnets to the marketplace - China’s tightening of its grip on REM exports has caused manufacturers to seek alternative IE4 technologies.

“Manufacturers have been very creative in dealing with magnet sourcing issues by producing drive technologies that reduce the number of neodymium magnets needed in a PMSM motor, or by producing IE4 class motors that use no magnets,” he says.

The report cites ABB’s Synchronous Reluctance motors and Nidec’s Switched Reluctance motors as being two examples of low voltage motors that achieve IE4 levels of efficiency without the use of magnets, and which have become viable lower-cost alternatives to the traditional neo-based PM machines.

While ABB has introduced a new technology, switched reluctance technology has been around for a while, but is being given a fresh look and a broader application horizon in an industry promoting energy efficiency. Mark Meza again:

“When discussing the industrial IE4 motor market in the past, the landscape was mostly limited to neo-based PM motors, or motors with copper rotors. Now, several proprietary designs that use traditional ferrite magnet technology must be included in the discussion as well.”

US-based NovaTorque produces an electrically commutated PM (ECPM) IE4 motor using traditional ferrite magnets, while Hitachi Metals has been at the forefront of developing an axial flux motor technology using amorphous metal ribbons made of iron, silicon and boron (FeSiB), coupled with traditional ferrite magnet technology to achieve an IE4 level of efficiency.

According to Meza, there are always application-specific pros and cons when considering the most appropriate motor technology to use. But in an energy-conscious world, having more alternatives, and at lower cost, will only help the industry. Currently, most IE4 class motor product lines are limited to the 1-5hp power ratings.

However, as industry acceptance increases with more affordable manufacturing cost structures, higher power-rated IE4 motors are expected to gain more traction in the marketplace.

To repair or to replace?
A recent blog post by European Automation's Jonathan Wilkins drew a question from yours truly - does the 'repair rather than replace' option indicate short term, recession-led thinking? Jonathan replies:

This is a big question for us at European Automation for two reasons. The first and most obvious is that we want to give the best advice to our customers, so that they return to us next time they need to source a part. The second reason is that, while we sell new components, and can even sometimes provide them more cheaply than the manufacturer, we also specialise in sourcing obsolete components.

Obviously new parts can be used for repair but just as easily find a home with a systems integrator, original equipment manufacturer (OEM) or machine builder who is replacing an entire system. In contrast, obsolete parts would normally only be used in repair and maintenance applications.  

I think it’s a question of balance. The repair option should run in parallel with a sensible approach to replacing equipment that genuinely requires replacing.

In many cases our customers come to us when production has been affected or stopped entirely, often because just one part is no longer available in stock from the manufacturer. In these instances repairing the part is not an option - it has to be replaced, often with an obsolete component.

As you can see, the lines are already blurring – we are replacing the component but repairing the system! And we are doing so to achieve a short term objective.

However, we are also often approached by companies who want a more energy efficient solution. It might be that they are running a packaging line using old fashioned, non energy-efficient motors.

In this case, the best option would be to replace the motor and drive combination, and possibly all the peripherals such as braking resistors, chokes, filters and so on, to make the overall system as efficient as possible.

Again, we are replacing components to repair the system, but this time it’s long term thinking, not short term need that is the motivation. The key is to think long term – what will the system cost to operate over its lifetime? Do not make decisions that will undermine that operation.

So, to try and answer Les’s question without muddying the issue, it’s the needs of the application that determines whether the solution is the result of short or long term thinking. Sometimes a repair represents long-term balanced thinking and a replacement represents a short-term recessionary and reactionary philosophy where sometimes it’s precisely the opposite!

Les Hunt


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