Using motors and drives to reduce operating expenses

IN the continuing push for greater energy efficiency in the manufacturing industry, there is now a strong focus on optimising efficiency of the components of entire power delivery systems, including the gearbox, the motor and the power electronics.

[Image, right: The latest glass-reinforced composite blades are said to be lighter and up to 10% more efficient than steel and aluminium blades.]

Matthias Neurohr, engineered drives and motors product manager with Siemens Australia, believes that in terms of energy efficiency of individual equipment, such as transformer and variable speed drives, the ceiling has almost been reached, and that most are now hovering around 98 to 99% efficiency.

“Rather than investing much more time and effort or by using highly sophisticated materials that would blow out the final cost and outweigh many of the benefits of fractional improvements, we recommend taking a step back and looking at an overall energy efficient solution,” Neurohr told Manufacturers’ Monthly.

“After all, energy efficiency is all about saving money while maintaining or improving productivity, thus increasing profitability, especially while the cost of energy continues to rise. "

But he says it should be recognised that availability of equipment and productivity go hand in hand.

“For instance, our Perfect Harmony medium voltage drive, which is used in the manufacturing and processing industries for motor powers starting at 150kW, features a system that allows the drive to continue operation after an internal fault. 

“This is due to a unique modular topology where the power section of the drive is divided into multiple, partially rated power modules that can operate independently from each other. 

"If one of the modules fails, the drive shuts that module down and isolates it from the circuit so the rest of the drive can continue to run.”

In relation to motors, Neurohr says that efficiency is not necessarily the prime objective for customers and that depending on the application or the supply infrastructure, efficiency has to take a back seat to more important requirements such as higher starting torque and lower starting current.

EC technology

Simon Bradwell, MD of ebm-papst A&NZ, major supplier of industrial fans, motors, actuators and drives says opportunities for reducing energy consumption through Electronically Commutated (EC) technology are huge and shouldn’t be confused with basic DC motors.

"Basic DC motors rely on carbon brushes and a commutation ring to switch the current direction, and therefore the magnetic field polarity, in a rotating armature. The interaction between this internal rotor and fixed permanent magnets induces its rotation.

“In an EC motor, the mechanical commutation has been replaced by electronic circuitry, which supplies the right amount of armature current in the right direction at precisely the right time for accurate motor control,” he explained.

“EC technology is a more cost effective alternative to AC technology, and it is also environmentally beneficial, reducing carbon emissions by at least 30%," Bradwell said.

He explains that AC motors are designed to operate at a certain point in their performance curve which coincides with their peak efficiency. 

"However, either side of this operating point, the efficiency can drop off considerably. EC motors on the other hand have an almost flat efficiency curve which varies relatively little across the speed range.

“Examples of how innovative motor technology and ventilation technology optimally complement one another are our Hyblade and RadiCal fans with a hybrid material structure. 

"We have moved from steel and aluminium to glass reinforced composite blades which are lighter and 8 to 10% more efficient.

“This combination of high efficiency impeller with high efficiency motor and speed control provides a total system solution that is powerful and energy efficient,” Bradwell said.

Integrated approach

Tony Sculpher, Nord’s regional sales manager for Victoria, Tasmania and SA, says Nord follows an integrated approach with the drives supplied with optimised overall efficiency.

"The energy efficient AC motors comply with all current standards and can be adapted to future standards.

“Also, all Nord gearboxes are manufactured according to the UNICASE principle which ensures wear-free and efficient operation because there are no sealing surfaces that could deflect under the effect of torque. 

"With helical inline gearbox units, the rolling motions are optimised in order to limit losses from mechanical friction to a minimum,” he said.

“Efficient geared motors can be combined with several lines of frequency inverters which feature an automatic magnetisation adjustment option. 

"This integrated function allows users to reduce magnetisation as required during partial load operation, thereby preventing unnecessary losses in the motor and considerably reducing power consumption,” Sculpher said.