By Eamonn Ryan from a SAIRAC Cape Town presentation
At the SAIRAC Cape Town Tech Talk, Marthinus Greeff from WEG South Africa discusses the vital topic of motor efficiency, emphasising its growing importance globally and its impact on South Africa’s energy landscape. The session highlights the need for more energy-efficient motors, especially with the upcoming regulatory changes in South Africa. This is Part 6 of a seven-part series.
The SAIRAC Cape Town Centre January TechTalk. SAIRAC Cape Town Centre.
A significant portion of the conversation focuses on the factors contributing to motor inefficiency, including:
- Iron losses (20%)
- Mechanical losses (5%)
- Stray load losses (10%)
- Resistance losses in the stator and rotor (40-50%)
Greeff elaborates on how resistance and the quality of magnetic materials, such as laminated steel used in the motor core, are major sources of inefficiency. To enhance efficiency, motors can benefit from increased copper content to reduce resistance and the use of higher-quality laminated steel, such as grain-oriented steel, to improve the motor’s magnetic properties.
The role of copper and steel in motor efficiency
Greeff provides an analogy to explain the role of copper and steel in motor efficiency. Just as increasing the number of coils in a magnet strengthens the magnetic field, increasing the copper content in a motor’s windings improves its performance. Similarly, better quality steel, like grain-oriented laminated steel, leads to more efficient magnetization, which reduces the current needed for the same magnetic field, ultimately improving efficiency.
Can efficiency be improved post-manufacturing?
A question arises about whether a motor’s efficiency can be quickly improved after manufacture. Greeff clarifies that superficial changes, like painting the motor green or making quick adjustments, will not improve efficiency. Efficiency improvements depend on the quality of materials, design and manufacturing processes, which cannot be retroactively altered after production.
The discussion highlights the complex nature of motor efficiency, the challenges of transitioning to IE3 standards, and the ongoing efforts to ensure that new motors meet the evolving needs of businesses while maintaining cost-effectiveness and compatibility with existing systems.
The green motor
Greef shares an interesting piece of history about the ‘green motor’. In the early 2000s, when the company was importing motors, there was no formal regulation requiring efficiency labeling on nameplates. To make it easier for forklift operators to identify which motors were more energy-efficient, the company came up with a simple solution: they painted the motors green. This was a quick and effective way to distinguish high-efficiency motors from others. The practice caught on, and soon, the ‘green’ motor became synonymous with energy-efficient motors, particularly those that met the IE3 standards. This initiative predated the widespread use of barcode scanning systems in warehouses, illustrating the company’s forward-thinking approach to operational efficiency.
Motors in large projects
Greef also highlights the company’s involvement in large-scale projects, such as supplying motors for the cooling system at the Maracanã Stadium in Brazil. This example demonstrates how high-efficiency motors are essential in major infrastructure projects, where energy efficiency plays a crucial role in reducing operational costs. The Maracanã Stadium, as one of the largest soccer stadiums in the world, required a significant focus on energy-efficient systems to meet both environmental and financial goals.
Key takeaways:
- Motor efficiency goes beyond the rating class: It’s essential to assess the entire efficiency curve, not just the efficiency class (IE1, IE2, IE3). Many motors, especially in fan systems, often operate below full load, so understanding efficiency at partial loads is crucial.
- Nameplate data is vital: Always refer to the motor’s nameplate for its efficiency ratings at various load levels. These provide a more accurate indication of how a motor will perform in real-world scenarios, where full-load conditions aren’t always met.
- Motor design and material quality influence efficiency: The motor’s efficiency is heavily influenced by its design and the materials used, such as copper and laminated steel. Proper resistance management also plays a significant role in improving efficiency.
- The origin of the green motor: The green color became a distinctive identifier for high-efficiency motors, starting in the early 2000s as a practical way to distinguish more energy-efficient motors in warehouses. Over time, it became widely associated with IE3-rated motors.
- Post-manufacture efficiency adjustments aren’t feasible: Efficiency improvements cannot easily be made after the motor is produced. Instead, any efficiency enhancements need to be integrated during the design and manufacturing stages.
