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Putting “energy efficiency first” into practice

The latest advances in variable speed drives and electric motors offer quick wins in the drive toward net zero.

In September 2021, the European Commission published new guidance aimed at moving its “energy efficiency first” concept from principle into practice. An immediate possibility is to use variable speed drives (VSDs) to control industrial electric motors. In typical applications this can cut energy consumption by 25%. Furthermore, if the drives feature the latest ultra-low harmonic (ULH) technology they can improve power factor for further gains in energy efficiency. Things gets even better when drives are paired with one of the latest IE5 (ultra-premium efficiency rated) synchronous reluctance (SynRM) motors.

Equipment using electric motors consumes around 45% of the world’s electricity, and accounts for about 70% of industry’s consumption, so the opportunity for positive change is huge. Far too many of the world’s estimated 300 million industrial electric motor-driven systems operate inefficiently. One immediate target should be those running pumps, fans and compressors, which make up roughly 75% of the total. In these applications, especially, there is scope to substantially improving efficiency. Overall, experts estimate that around 50% of industrial motors would benefit from being paired with a drive, but only 23% are currently equipped in this way.

VSDs optimize motor operation

A VSD controls and optimises the operation of a motor by adjusting its speed and torque to meet the changing requirements of the system. Without it, the motor either runs constantly at full speed – whether or not that is necessary – or has to be regulated by energy-wasting mechanical speed controls such as valves, gears, throttles or brakes. Importantly, there is a non-linear relationship between motor speed and energy consumption which means that even a small reduction in speed can result in significant energy savings. In some cases, for instance, slowing a pump or fan motor by just 20% is enough to halve the amount of energy it uses.

Eliminate harmonics and boost power factor

With the many advantages of VSDs comes a potentially troublesome power quality issue in the form of power line harmonics that can have an adverse effect on both system reliability and energy efficiency. If not addressed, harmonics can trip circuit breakers, blow fuses, damage sensitive equipment and cause overheating of cables, motors, generators and capacitors, wasting energy and shortening their life.

The latest generation of ultra-low harmonic (ULH) drives have harmonics mitigation built in, creating a simple installation that offers significant savings in space, time and money.

In addition to mitigating harmonics, ULH drives also have the capability to improve the power factor (PF) that describes how effectively an electrical network uses the power it draws. In the very best case, a network will have a PF of unity (1) – that is quite rare. In some cases, utilities will impose penalty charges on buildings with a poor power factor. Essentially, ULH drives not only optimize the energy efficiency of industrial processes, they help make the overall power network more efficient. The result is lower electricity bills.

New advances in high-efficiency motors

The last ten years have seen rapid advances in both drive and motor technology. These combine to great effect when a VSD is partnered with a high-efficiency SynRM motor. It is only in the last decade or so that sophisticated VSDs have been able to unlock the full potential of the SynRM motor concept and take energy efficiency to the next level.

A new minimum international efficiency (IE) standard, IE3, covering most low-voltage motors, was introduced in July 2021 under the EU Ecodesign Regulation. However, ABB is already offering SynRM motor and drive packages which meet a much more demanding rating, IE5.

Pairing an IE3 induction motor with a VSD will typically reduce energy bills by up to 25%. Replacing that combination with an IE5 SynRM and VSD package can add a further saving in the region of 3 to 4%. The exact amounts will depend on the application and conditions.

Given that most motors in the current industrial installed base are over ten years old, replacing them with optimised, high-efficiency motor and drive packages would make a considerable difference. A reasonable estimate is that global electricity consumption could be cut by 10%, with a consequent reduction in CO2 emissions.

An upgrade that soons pays for itself

For businesses using electric motor-driven equipment, the investment in upgrading to a VSD and SynRM motor package can be justified easily on the basis of energy savings alone. Crucially, the purchase price of a motor is just a small fraction of its lifetime cost, as most of the expense lies in the energy needed to run it. A SynRM motor and VSD package will initially cost a little more to buy than an IE3 motor and drive, but its energy savings will often pay back the difference in as little as a year. After that, it will continue to generate annual savings for the next ten years or more.

A win-win situation

Energy efficiency has been a key element of EU policy on emissions reduction for some time, and the “energy efficiency first” principle is officially written into EU law under the 2019 Governance Regulation. Now it is time for practical action to implement that principle. Thanks to the technological developments outlined here, electric motor users are in a great position not only to help drive industry toward net zero but to cut their electricity costs and boost their productivity.

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