Improving motor efficiency

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Selecting the right energy efficient motor can deliver significant cost savings for local manufacturers. 

When it comes to assessing the energy efficiency levels of motors, manufacturers need to consider the design of the motor in context of the application and operating system it is used.

Brett Motum, Maxon Motor's Australian MD, says the prime focus for manufacturers should be the design principal and quality of a motor.

"Some motors by design are more efficient than others. For example, if a motor contains a laminated stack then eddy currents which represent a loss are generated within the iron laminations," Motum told Manufacturers' Monthly.

"From a design standpoint, companies can select an ironless motor to eliminate this loss altogether or from a quality standpoint they can select a motor with very thin iron laminates and higher grade metals to reduce this eddy current loss."

Motum says there a huge number of additional factors to consider at this point, such as bearing type and quality, the air gaps within a motor the type of magnets and so on.

The importance of considering factors other than design was also noted by Frank Cerra, SEW-Eurodrive Australia engineering manager.

"What it also comes down to is not only the motor, but what the motor is driving," Cerra said.

"Manufacturers and motor users shouldn't just look at the motor in isolation. They also need to look at the type of gear box, the process that is being driven by the motor and how they are doing things in order to improve their efficiency.

"They might have a super premium efficiency motor, but if coupled with a very inefficient gear box, they would have lost all the efficiency gains from the motor."

"They need to look at the whole system, not just the components in the system," Cerra said.

Non-compliant motors

Once a non-compliant energy efficient motor is already installed in application, it is then difficult to get that motor to meet energy efficient standards.

Motum says applying a "band aid solution" will not bring about greater motor efficiency. "The most gains to be made here are on the controller side.

"If speed, torque or position control is required for the application there are newly released controllers on the market with over 95% rated efficiencies," Motum explained.

However, he says the main loss is in the conversion of electrical to rotary.

"The mistake made most often here in Australia is a result of familiarity. An engineer with a machine to build will select the motor he knows and has always used.

"Sticking with something you know is eventually going to mean you are not going to be using a motor design with the latest advancements."

Motum says common mistakes companies make is operating manufacturing equipment with large AC motors to move tiny loads or companies asking for a 1hp motor, or a 10 or 20A motor without knowing the efficiency or the load requirements.

"There are motors available that meet and exceed the highest global efficiency standards we just need engineers to be mindful of this during the selection process," Motum said.

Energy performance

In Australia, the current efficiency standard is AS1359.5 2004. There is also the international standard IEC60064-30, which is currently under review for a second edition.

In its current form, the international standard defines all efficiency levels and assigns each level of efficiency percentage figures for each motor power rating.

Levels include IE1, which defines the motor as old and non-efficient, IE2 which classifies motors as high efficiency, IE3 for premium efficiency motors, and IE4 which is for super premium motor efficiency.

To make sense of this, Cerra explained that most motors in the IE2 category – the most popular and common energy efficient level for motor choice – typically meets Australian energy efficiency standards.

This according to Cerra, is a good indicator that local standards are in many ways on par, if not higher than international standards, and the need for improvement is not so immediate.

"The Australia standard is high in some areas; there are some differences compared with the international standard, but overall the local energy efficient standard is higher," Cerra said.

As an example, Cerra says, the Australian standard still covers 8-pole motors, where as the international one doesn't. However he believes that the two standards will blend once a review of the international standard is completed and the new IEC standards covers 8-pole motors.

[Image: EC 8 Motor from Maxon Motor Australia, courtesy of ferret.com.au]