Motors & Drives: In Search of Energy Efficiency
While energy efficiency continues to remain the dominant trend, other important changes are driving research for better and more efficient motors.
Electric motors are widely used in all spheres of life – domestic, commercial and industrial. Each application needs a specific type and size of motor, which broadly is available in two types – AC or DC based on operating current – with further classification in each type based on types of construction, winding, number of poles, etc. There are also servo motors or stepper motors, which are used for precise positioning applications and not in the purview of this article. As for the size, motors today are available in miniature and even nano sizes at the smaller end, and the largest is reportedly rated at 135,000 HP, used to rotate a fan of a wind tunnel at NASA.
Major applications of motors are in domestic appliances, various types of machinery and process equipment, industrial fans and blowers, compressors, pumps, machine tools, HVAC applications, disk drives, power tools, electric cars and automated robots to just name a few. For the record, the three-phase squirrel cage induction motor is the most commonly used motor and has the largest market share.
According to a research report published by Markets And Markets, a leading global marketing research company, the global electric motor sales market is expected to grow from an estimated USD 94.23 bn in 2016 to USD 127.63 bn by 2021, at a compounded annual growth rate (CAGR) of 6.26% from 2016 to 2021. Major growth drivers for industrial motors are the rising production and expansion in end user industries. Factors driving the electric motor sales market include growing motorised automation across major industries, increasing motor-driven household appliances, continuously growing agricultural sector, strong automobile production, and transition toward energy-efficient motors.
IndustryARC, another leading provider of market research reports, custom consulting services, data analytics and industry analysis, reports that the North American region with the newly expanded oil reserves, has a substantial market for industrial motors used in Oil & Gas industry, and is projected to have a substantial growth. But it is the Asia-Pacific (APAC) region that holds the biggest share of the market due to the large growth in industrial production mostly in China, India and other South-east Asian countries. Experts estimate APAC industrial motors market to have a highest CAGR during the period 2016-2021.
Most major motor manufacturers just do not offer motors but also have a wider range of geared motors – a combination of motor and gearbox of fixed and/or variable ratio. Typically, gearboxes are connected to the motor shaft, reduced the speed to the desire ratio, and increase the torque proportionately for various industrial applications. This is integrated mechanical speed control option and not to be confused with speed variation by AC drives or other devices.
It is a field dominated by a few large players and many smaller ones, led by the likes of ABB, GE, Siemens, WEG, Toshiba, SEW Eurodrive, NORD, Lenze, Bonfiglioli among others. Besides, there are companies like Atlanta (Georgia, USA) based East West Manufacturing, one of the largest contract manufacturers of electric motors for OEMs, backed by a global supply chain for components and sub-assemblies, producing world class motors at multiple locations.
Electric motors are the single biggest consumers of electricity. They account for about two thirds of industrial power consumption and about 45% of global power consumption, according to an analysis by the International Energy Agency. It is no surprise that energy efficiency in motors today is a critical issue, and that is where the association of motors with drives begins. Over the years technology has made the construction of motors compact, materials lighter, insulation more effective and as a whole, increased efficiency.
The International Electrotechnical Commission (IEC), the world’s leading organisation for the preparation and publication of International Standards for all electrical, electronic and related technologies, has developed an internationally applicable testing Standard IEC 60034-2-1 for electric motors and a classification scheme IEC 60034-30-1 with four levels of motor efficiency ("IE-code"):
- IE1 Standard efficiency
- IE2 High efficiency
- IE3 Premium efficiency, and
- IE4 Super premium efficiency.
In simple terms, an energy efficient motor is one that gives the same output with lesser input, i.e., electricity. Estimates suggest that if all the motors in the world are replaced by IE4 grade, several hundred power plants will be rendered useless globally, such is the potential of the resultant savings in electricity. For example, the efficiency of IE4 motors is 14% higher than for IE1 motors, which is the highest gain. Of course the main reason why users do not switch over to better motors is the cost. An energy efficient motor is costlier by 15% to 30% compared to a standard motor, and even if the payback period in terms of energy saved is short (about two years), there is reluctance to invest in better technology, and compromises made while buying new motors. More serious is the case of repair and refurbishing of old motors, which are worse than contemporary standard motors in terms of energy efficiency. So the rising trend for repair rather than replacement is a major challenge in the aftermarket.
AC Drives make motors more efficient
Right at the outset when motors were first designed and manufactured in the 1880s, DC motors had an advantage over AC motors in terms of speed regulation since the former could be controlled by a simple rheostat. Controlling the speed of AC motors was more complex, and it took almost 100 years before an effective solution was found in the 1980s. The situation then changed rapidly in favour of AC motors as these are more efficient with effective speed control, though there are applications even today where DC motors are better suited. Today, both types of motors – AC and DC – have very efficient devices or drives for speed control. Both types of drives have many versions and options catering to specific application requirements. What drives actually do is offer efficient speed control, adjusting the motor's speed to closely match output requirements as per the load conditions, and further add to the savings and benefits accrued by the use of energy efficient motors. Drives typically result in energy savings of 10 to 50 per cent.
A DC drive is an electrical device used to regulate the speed of a DC motor by controlling the input voltage and/or amperage to the DC motor. It also rectifies the AC power input into DC feed for the motors. Its primary advantages are increased energy savings and reduced motor wear. The global DC drives market, according to a study by Markets And Markets, will grow from an estimated value of USD 2.1 billion in 2015 to around USD 2.3 billion by 2020 with a CAGR of 2.5% from 2015 to 2020.
AC drives, commonly referred to as Variable Frequency Drives (VFDs) are known by many other names like Adjustable Speed Drives, Adjustable Frequency Drives or Frequency Converters, and have today become widespread in use, ranging from smaller appliances to larger motors in commercial, agricultural and industrial applications. According to a report by Research & Markets, the VFD market is projected to reach USD 24.8 billion by 2021, at a CAGR of 5.94% from 2016 to 2021. VFDs are used in infrastructural activities which include commercial buildings such as hospitals, and educational institutions. Increasing urbanisation and industrialisation in developing countries such as India, growing need for energy efficiency, reduction in operating costs of any energy intensive industry, regulations on energy efficiency, growing trend of industrial automation, and regulations to ensure efficiency are expected to drive the variable frequency drive market.
While energy efficiency continues to remain the dominant trend in motors, there are some other important changes that are driving research for better and more efficient motors with the combined contribution of better design capabilities, lighter materials, stronger permanent magnets and more efficient cooling. Most leading manufacturers now offer motors with fully integrated drives and electronic controls.
So the quest for higher motor efficiency continues.