OEM Sustainability: Energy Efficiency for Machines

Purchase price of a machine accounts for just 2%-3% of its overall cost. Making intelligent choices when choosing motors can save up to 30% of energy consumption over the life of a machine.

12/25/2011


Industry and infrastructures consume more than 31% of available energy globally, with electrical motors alone representing more than 60% of this amount. With the increasing cost of electricity, intelligent consumption is a major concern for users and manufacturers.

(1) Using a motor with higher efficiency saves up to 10% energy. (2) A variable speed drive to control a motor saves up to 50%. (3) Using a servo drive and synchronous motor brings an additional 30% of savings, compared to standard drives in positioning a

When a decision is made to acquire a new machine, a manufacturer should consider the amount of energy that will be consumed by this machine during its lifecycle. Among expenses from the acquisition to dismantling of a machine, the purchase price accounts for 2% to 3% of the overall costs; the remainder is mainly its energy consumption. Smart solutions exist today to make the most of the available energy.

Machine engineering can be a key source of improvement in the energy consumption of machines. A machine is designed according to performance criteria and productivity. The engineer’s goal is to find the most efficient, economic, and competitive solutions—and motor selection is the result of these choices.

Generally, the selection is finalized when the mechanical part is defined and the power consumption is typically not taken into account; however, the growing cost of energy imposes new strategies. The choice of the motor should be the starting point of any reflection to reduce the power demand. Considering the mechanical requests, the motors that will equip the machine must answer several criteria.

First, motors allow machine continuous operation and provide the needed torque at the rated speed. This first consideration determines the motor size. The designer must also consider the motor torque requested to start the machine. Eventually, the motor may have to be oversized. Duty cycle is also a key point—any time the machine is started, there is a motor heating and it is essential not to exceed a limit which, at last, will end with the failure of the motor.

Generally speaking, a motor’s energy bill is motor cost x 100. Beyond the investment, the key point is to secure an efficient motor control. During a motor’s average 15-year life, 1% of the cost is capital investment, 2% is installation and maintenance, a

The ultimate decision is based on the environmental conditions and will take into account the temperature and the altitude at which the machine is due to operate. When all these evaluations are made, the selected motor is usually larger than necessary for continuous operation. As the motor is not running at its rated power, its efficiency is reduced. That inevitably leads to increased energy consumption. Due to motor and machine efficiency, part of this energy is simply wasted.

A closer examination of the machine, its modes of operation, and dynamic performances is the best way to choose the most suitable motor technology. Making intelligent choices when choosing motors can save up to 30% of energy consumption over the life of the machine.

- Ian Hitchins is vice president of OEM solutions, Schneider Electric. Edited by Mark T. Hoske, CFE Media, Control Engineering, www.controleng.com.

www.schneider-electric.com 

controleng.com/motors



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