Is copper the answer?

Published:  07 November, 2007

Is copper the answer?

 

Motors are everywhere in industry and business, powering everything from pumps and fans to compressors.  They are also major energy users and offer enormous potential for energy saving.  PWE looks at the issue of energy efficiency for motors and whether copper rotors may provide part of the solution for industry.

 

There is no better way for industry to start the process of energy saving than taking a close look at its motors and drives.  Often, motors are tucked away in air ducts and out of the way places, going unnoticed for months on end barring a regular service or malfunction.

However, the humble motor can make an enormous contribution towards energy saving.  Data from the Carbon Trust suggests that a motor running for 11 hours a day (4000 hours a year) at a typical industrial or commercial site costs ten times more in electricity than in capital cost. 

With efficiency becoming such an important issue, manufacturers across Europe established three efficiency bands EFF1, 2 and 3 more than five years ago.  Figures compiled by Siemens demonstrate that when you take into account the complete lifecycle costs, the difference in the environmental impact between EFF1 and EFF2 motors, according to the GaBI technique, exceeds 20% (GWP 100 for 7.5 kW).

Many companies are therefore beginning to make the move from EFF2 to EFF1 motors, with the latter using new technology such as the use of copper rotors.  Traditionally, there have been two ways of motor manufacturers achieving greater motor efficiency, predominantly either by using additional materials or higher-grade metals. In recent years, Siemens for example, says it has used considerable research and development resource to analyse the second option, in particular the use of aluminium in combination with copper rotors to increase the efficiency of its motors.

This type of motor, such as the Siemens 1LE1 motor, is claimed to be between 20 and 30 % lighter than comparable three-phase induction motors, due to the combination of aluminium frame and copper die-cast rotors. This lower weight has a positive impact on the handling of the product, as well as the size and positioning within the mounting space in the machine or equipment.

The rotors however can play the most significant role in achieving increased energy efficiency and can now be manufactured using a copper die-cast technique despite the ability to handle copper technology being one of most demanding disciplines when it comes to building electric motors.

This type of mechanical design can also offer engineers the flexibility to select a higher efficiency class at a later date without having to make mechanical design changes.  Situations always arise where plant and system planning phases result in extremely long implementation times.  If the price of energy continues to rise, for example, or if unfavourable contractual changes are signed with power utility companies, then "profitable" kilowatts can be saved "at the last minute".

In practice, all of this means that the mechanical design and planning of machines and equipment is not made more expensive when changing over from EFF2 to EFF1 motors in spite of the fact that energy-saving motors are being used.  This sort of modular design can also reduce the number of different parts and components that are essential for use in compact motors, for example.  The increased power of this motor type can also use the next smaller frame size even for the same power rating for EFF1 as well as the EFF2 motors.

The amount that is actually saved when changing over from EFF2 to EFF1 differs depending on the situation. However, Phil Batley, product manager - Low Voltage Motors, of Siemens Automation & Drives,  highlights efficiencies can be measured using technology such as the Siemens "SinaSave" program, which was predominantly developed for the process industry and takes a holistic view of the drive application.  He explains: "Pressure levels, flow rates, delivery heights, specific gravities/densities, power ratings and a lot more information are included within the calculation.  Even the individual electrical efficiencies are taken into consideration. This means that different drive concepts - for instance pump and valve control, as well as EFF1 and EFF2 motors can be compared with one another from an energy perspective. The program then precisely calculates the corresponding energy saving – therefore addressing the demand for energy-saving solutions.”

To give an example of potential savings involving a medium-sized industrial pump - typically, the energy costs represent 46% of the operating costs. Batley says the reason for the high energy demand of many pumps, fans and compressors is the fact that a traditional control technique is used where mechanical actuators regulate the flow.  In many cases however it would be more advantageous to use variable-speed drives in conjunction with energy-efficient EFF1 motors.

He adds: “The new motors retain the current flexibility in terms of their modification compatibility, such as the fitting of brakes, encoders, motor protection, anti-condensation heaters and increased lp rating. In addition, the new 1LE1 motor can be modified in both its EFF1 and EFF2 forms and all modifications can be carried out locally by authorised Motor Partners.”

The use of aluminium construction motors and copper rotor technology has allowed Siemens to reduce the length of the EFF1 motor and hence provide significant weight reductions.

 

 

For further information please visit: www.siemens.com

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