Motors and drives form the backbone of industrial processes. Estimates suggest that these account for nearly 70 per cent of the industrial electricity consumption and around 40 per cent of the commercial consumption. Therefore, it is essential to optimise energy use and adopt measures to enhance energy efficiency in motors and drives. Energy efficient motors (EEMs) have a potential to significantly lower energy costs and environmental effects. Since electric motor systems account for a sizeable portion of all electricity consumption, using EEM systems in both new installations and accelerating the replacement of old inefficient motors could result in significant cost savings.
While upgrading a motor can result in significant efficiency benefits, using a high-efficiency motor in conjunction with a variable-speed drive (VSD) can result in even more energy savings.
The majority of motors in India use a lot of energy and are inefficient, which causes problems such as high operating costs and significant emissions from industries and power plants. Around 90 per cent of the motors that are now installed are estimated to be at the IE1 and sub-IE1 levels. Additionally, because the majority of these motors have been operating for 15 years or longer, they frequently fail and need maintenance. The operations and maintenance (O&M) costs of industrial units are substantially increased by the use of inefficient motors.
National Motor Replacement Programme
EESL is accelerating the adoption of IE3 motors for motor replacement under the National Motor Replacement Programme (NMRP). The customer is not required to make any upfront payments under the programme. By monetised energy savings, EESL is repaid. The programme aims to replace the currently installed lower efficiency motors, which are old and have been rewound multiple times over their lifetime, with new IE3 motors. Under this programme, EESL is offering IE3 motors ranging from 1HP to 100 HP to Indian industries. This programme is advantageous for MSME as well as non-MSME industries.
According to an estimate by EESL, more than 2 million motors produced in the country have the potential to save more than 5 billion kWh annually, or $500 million per annum, which might result in avoidance of 600 MW of generation capacity. In the initial phase, EESL plans to replace 120,000 motors. The NMRP in India conducted 36 motor pilot studies in the cities of Ahmedabad, Surat, Jamnagar and Mumbai in 2018. It found power savings across all pilot installations by swapping out standard efficiency motors with premium efficiency IE3 motors in compressors, pumps, fans and blowers used in the brass, textile, chemical and automotive industries. The NMRP began exploring the possible effects of upgrading 5,000 standard efficiency motors at major corporations and small and medium enterprises nationwide. It came to the conclusion that the action would result in 9,150 MWh of yearly energy savings, $902,112 in annual cost savings and 8,050 tonnes of annual carbon dioxide emission reduction. During 2021–22, EESL deployed 1,920 IE3 motors. As on March 31, 2022, 5,280 IE3 motors have been deployed in the industry.
Energy efficient motors
EEMs are motor designs that include design advancements intended to maximise operational efficiency over conventional/standard motor designs. Reducing intrinsic motor losses is the primary objective of design advancements. The use of lower-loss silicon steel, a longer core (to increase active material), thicker wires (to reduce resistance), thinner laminations, a smaller air gap between the stator and the rotor, copper bars instead of aluminium in the rotor, better bearings, a smaller fan and other advancements. The country’s EEMs operate with efficiencies that are typically 3-4 per cent greater than those of conventional motors. According to the requirements of the Bureau of Indian Standards, EEMs are developed to function efficiently with loads ranging from 75-100 per cent of their rated capacity.
This has significant advantages in a variety of load applications. Moreover, EEMs are often more capable of accelerating higher-inertia loads and are less impacted by supply voltage variations. They also operate at lower operating temperatures and noise levels.
Variable speed drives
Without the intervention of a variable speed drive, an electric motor lacks the ability to regulate activity and is only capable of operating at its maximum capacity. Alternatively, by including a VSD into the system, the drive can cut or lower the motor’s output and save energy when a pre-set condition, such as temperature, is met.
Installing VSDs in motors is thus another energy-efficient technique to increase motor efficiency. In accordance with the requirements of the application, VSDs alter the speed of an electric motor. Without this adjustment, the system brakes when less power is needed, wasting energy and releasing it as heat. VSDs thus conserve energy with each spin. Industry estimates suggest that slowing a fan or pump motor from 100 per cent to 80 per cent with a VSD can save energy consumption by as much as 50 per cent. In a fan application, for example, VSDs regulate the airflow in accordance with requirements rather than abruptly stopping it when operating at full capacity. Pumps, fans, and compressors are industrial motors where VSDs are most frequently installed because of their frequent and intermittent use due to time, temperature and output requirements.
Other emerging trends
- Digitalisation of operations: Existing motors can be equipped with wirelessly connected sensors, allowing for remote and transparent performance monitoring. The collected data can be used to optimise processes and realise considerable efficiency gains and energy savings in a complicated industrial installation or HVAC system of a large structure. When the monitored motors are remotely or automatically controlled, their performance, system efficiency, and energy savings are further enhanced, making them smart motors. The data produced by sensors can be analysed along with other control data and used by a central control system as the foundation for real-time modifications to the entire installation.
- IE5 grade motors: In recent years, companies have launched the IE5 grade of motors, which incorporate synchronous reluctance technology, to improve efficiency and operational performance. The rotor in a synchronous reluctance motor has no magnets or windings and suffers virtually no power losses. And because there are no magnetic forces in the rotor, maintenance is as straightforward as with induction motors. These motors combine the performance of permanent magnet motors with low O&M cost of induction magnets, to maximise efficiency and minimise downtime. Additionally, the absence of magnetic force in the motor helps reduce temperature in the motor, thereby prolonging the lifetime of the motor and improving its reliability.
- Soft starters: Soft starters can be used in plants and industrial units to increase the efficiency of motors that are only sometimes or partially in use. The load, torque and start-up electric current surge of the motor are all temporarily reduced by these devices. A slow starter for machinery saves energy and reduces mechanical stress on the motor and shaft. A soft starter can result in cost savings over the motor’s lifespan, including reduced energy expenses and lower maintenance costs.
- Closed-loop control systems: By comparing the desired output condition with the actual output condition, closed-loop systems are intended to automatically achieve and ma-intain the condition. The error signal, which is the difference between the output and the reference input, is produced in order to achieve this. A closed-loop control system’s key benefit is its capacity to lessen a system’s sensitivity to outside disturbances and enhance an unstable system’s stability, among others.
For the system to operate better overall in the future, motor and drive systems must be properly maintained. Effective maintenance programmes can help companies avoid costly production interruptions by reducing the risk of unplanned downtime. Moreover, considerations including operating time, ambient conditions, and failure consequences should be taken into account when inspecting motor and drive system components. To get pollutants out of the engine, these examinations should be done alongside cleaning.
Overall, EEMs and VSDs are intended to be adaptable and dependable. They offer significant power consumption savings over earlier systems due to their outstanding efficiency. Electric motors in buildings and industrial applications account for a sizeable portion of the country’s electricity consumption, therefore, any investment made to upgrade the equipment will pay off in the long run, in terms of efficiency and sustainability.