Energy Efficiency of Machines: the Choice of Motorization
Intelligent use of electricity is a major concern for users and manufacturers. A recent paper published by Schneider-Electric and written by Alexander Perrat compares the technological capabilities and limitations of AC and synchronous motors, showing that a synchronous motor allows up to 20 percent energy savings while increasing performance.
Industry and infrastructure consume more than 31 percent of the available energy in the world, and electrical motors alone represent more than 60 percent of that energy consumption. Thus, when considering the decision to purchase a new machine, companies should take into account the amount of energy which will be consumed by the machine during its lifespan.
Among expenses from the acquisition to dismantling, the purchase price accounts for only 2 to 3 percent of the overall costs, the remainder of the expense primarily being energy consumption. Moreover, designing a more energy efficient machine creates cost savings over the lifetime of the equipment.
The paper identifies several solutions that can help improve the energy efficiency of machines. These include:
- Enhancing machine efficiency
- Operating modes that switch off an unloaded machine
- Utilizing variable speed drives
- Creating more efficient motion control solutions
- Using high efficiency motors
Pick the Right Motor
With energy costs continuously rising the choice of the motor should be the starting point in order to reduce power demand. Considering the mechanical requests, the motors which will outfit the machine must match several criteria.
First, they allow the machine to have continuous operation and provide the needed torque at the rated speed. This consideration determines the motor size. The designer must also consider the motor torque required to start the machine. Eventually, the motor may have to be oversized.
Duty cycle is another key point. Any time the machine is started, a motor heats and it should not exceed a limit which will lead to the failure of the motor. The ultimate decision is based on environmental conditions and will take into account the temperature and altitude at which the machine will operate.
In order to save fossil fuel resources, the European Union stated that by 2020, all motors in the field must be IE3, in other words, high efficiency motors.
With the use of high efficiency motors and available solutions, energy savings could reach 202 TWh per year in Europe alone. This represents 45 nuclear power plants in the 1000 MW range, 130 power stations using fuel, or 3,8 times the totality of the energy produced by wind farms (value 2007), the report shows.
Effects on the environment can be estimated at 79 million tons of CO2 reduction and a drastic reduction of nitrogen and sulfur oxides.
Conclusion
Traditionally, an AC motor is used in machines. This motor is designed to operate at a constant speed. However, using electronic drives with this motor improves the flexibility of the machines.
The synchronous motor is another solution.
The results of the study indicated that the replacement of a 1,5 kw AC motor with a synchronous motor of an identical size, generated nearly 30 percent more energy savings. The use of a dedicated controller would further improve performance dynamics and efficiency.
Read more: http://www.schneider-electric.com/en/download/document/998-2095-02-04-12AR0_EN/
