Reducing Energy Consumption Starts with the Motor

The latest Ecodesign regulation to be introduced in October 2019 is EU 2019/1781. This outlines two phases for progressing energy efficiency levels further and applies to low-voltage induction electric motors rated at less than 1,000 V alternating current (AC) and to variable speed drives (VSD) – also known as frequency inverters. See figure 2 for an overview of the IE norms.

Making IE3 mandatory in Phase 1

In July 2021: 

• It became mandatory for all 0.75kW – 1000kW motors, 2-4-6-8 pole, to meet the IE3 Premium Efficiency rating. It is no longer possible to combine an IE2 motor with VSD to achieve the IE3 efficiency levels. 
• The regulation covers 3-phase single-speed motors 50 Hz, 60 Hz, 50/60 Hz for direct-on-line operation with continuous duty defined as S3 ≥ 80% and S6 ≥ 80%.
• The regulation also applies to motors that have previously been exempt, for example, ATEX motors with protection types EX ec, EX d, Ex de, Ext, motors with IC418 cooling, and break motors with external brake.
• IE2 efficiency levels are mandatory for 3-phase motors with rated output from 0.12 kW and below 0.75 kW. 
• It is also compulsory for all VSDs between 0.12 and 1,000 kW to have a power loss corresponding to a minimum of IE2. 

There are a few exceptions to this, as set out in figure 2.

As such a vast percentage – 97% – of the TCO is entirely down to the cost of electrical energy, it is clear that this is where you can make most gains. Considering TCO rather than just the initial investment is vital for making cost savings. 

For example, the cost of a typical IE4 55 kW 4-pole motor is €3,264, yet the energy cost for running that motor 24/7 is a staggering €50,206.90 (assuming an energy cost of 0.1 €/kWh (see figure 4). 

You may be tempted to opt for equipment with the lowest capital cost as it is seemingly seen as a ‘better deal’. However, such immediate cost savings may prove to be detrimental to profits. Considering higher energy efficient products, means that life cycle costs are reduced, improving cash flow in the longer term.

Calculating the TCO enables you to make informed decisions on the most cost-effective motor solution. While working out TCO has traditionally been challenging, the development of online TCO calculators means you can now have all the information at your fingertips more easily. For example, the ERIKS TCO Motor Calculator takes into account the application’s running hours and energy costs and gives a clear comparison of repair, replace and upgrade options. 

Figure 5 shows a comparison of motors using ERIKS TCO Motor calculator. If you stipulate a motor needs to operate for 22 hours per day, 365 days per year and at 100% load, with an expected lifespan of 15 years and energy cost is 0.08 €/kWh, the calculator provides the two best options of motor. In this case, an IE4 motor provides lifetime cost savings of €26,422.90 and an ROI of 1.5 years and an IE3 motor would deliver a lifetime saving of €22,148.29 and ROI payback of 1.4 years.

When a motor fails, repair is often considered initially. This is often seen as a quick-fix and can seemingly cost significantly less than a new motor at first glance (depending on the repair necessary). 

However, this could be a false economy a 20-year-old motor that needs regular maintenance and repair will cost you more in the long term. Swapping an older motor with a more modern one, that has been built with energy efficiency in mind, will pay dividends in the long run. If your motor fails, you will need to repair it anyway, or buy a new one. The minimal investment you will need to make is the repair cost. So, if you should choose to buy a new motor, you can subtract the repair cost from the price of the new motor, reducing the total amount of the investment you need to earn back, thus improving the ROI.

For example, in a food industry application, replacing an old fan motor with a newer, more efficient one, proved to have a pay-back of only 10 months and be more cost effective. The existing motor had a power of 110 kw and an efficiency of 91.6%, and was going to cost €3,950 to repair. The new WEG 90kW IE3 motor had an efficiency of 95.6% and investment cost of €6,745. The savings, as shown in figure 6, were calculated to be €65,840 over the lifetime of the motor, and CO2 emissions of 196 Tons.

Selecting the right motor is key to improving reliability and energy-efficiency, but there are also other ways to reduce energy consumption and maintenance costs. The complete drive-chain should also be looked at to have maximum impact on cost savings. Working with trusted partners who have full knowledge of the most energy efficient solutions can pay dividends when it comes to understanding where savings can best be made. 

For example, VSDs can play a major role in enhancing efficiency while ensuring reliable performance and reducing maintenance costs. Investing in highly-efficient electric motors combined with VSDs can translate into operational savings as large as 20%. 

The largest savings can be made with quadratic torque applications, such as centrifugal pumps or fans where the flow is regulated with a throttle valve. By mitigating the throttle valve, and regulating the motor speed with an inverter, we can achieve enormous savings. Much higher than improving the motor efficiency. ERIKS can assist in calculating these savings and the associated ROI, as well as performing the change.

Moreover, it is important to review the motor sizing to check whether the right equipment is being used for the job. For example, does the application have the right size motor, or can a smaller, more efficient one be used instead? Power analyzers are critical here. They can be used to measure the power that is actually required in the system, so the motors can be sized accordingly. The reason for this, is that the efficiency of an electric motor drops exponentially when the load gets below 70% of the nominal load. Mainly in the past, but still today, manufacturers tend to oversize the motor because they don’t want to take any risks. 

Also, we can look at other drive train elements that consume energy and reduce the overall efficiency. Chains and belts are often not perfectly dimensioned, and sometimes even not necessary at all. It is possible to analyse the entire drive train and propose the ideal setup in regard to the customer’s needs. 

In one application at a dairy company, a 30-year-old 132kW 4-pole motor was used to run a cooling compressor. However, a power analyser showed that the motor only had a power consumption of 88.9kW. The motor ran for 8,000 hours per year with a total energy consumption of 711,200 kWh. The electricity cost was 0.06 ct/kWh, and resulting total energy costs were €42,672 per year. 

Since the power analyser proved that the motor required only approximately 90kW, the company upgraded their motor to a smaller and more energy-efficient IE3-rated 90kW one. After installation a new energy measurement was taken. This showed the power consumption was reduced even further, to 82.5kW. Total energy consumption was now calculated as 660,000 kWh with at a cost of €39,600 per year.

As a result of investing in a new, smaller, IE3 motor the company was able to save a staggering €3,072 per year. The ROI was 1.92 years.