By Dr Mark Gardiner, Director at Sprint Electric
Manufacturers are under continuous pressure to improve efficiency whilst maintaining the highest quality of product. Both can be made significantly more difficult with high current harmonics. If unmitigated, harmonics increase losses, reduce reliability, and can trigger surcharges that show up directly on a manufacturer’s energy bill.
Dr Mark Gardiner, director at Sprint Electric, explains the importance of harmonics in motor control and how power factor will become an increasingly important issue for manufacturers in the future.
The impact of harmonic distortion
There are two key problems with high harmonics. Firstly, harmonics, other than at the fundamental frequency (50 or 60 Hz), do not contribute to the power that the end application requires. For example, if you have a motor mixing material, there will be a certain power requirement, and higher harmonics don’t contribute anything to this power.
In a 50 Hz system, only the 50 Hz component of current transmits real power to the load. The higher-order components (5th, 7th, 11th harmonics), do not contribute any power to the application and instead create losses in the cables, the switch gear and the transformers, through I²R losses heating.
Beyond this, high harmonics consume valuable system capacity and shorten component life. They also distort supply voltage at the point of common coupling, creating problems for other users, destabilising the grid and damaging supply transformers.
Rising energy costs
As energy costs have increased over recent years, our customers have become more focused of minimising the harmonic draw of the drive to reduce consumption. Coupled with surcharges from the energy supplier, a poor power factor leads to inefficiency. If businesses maintain a power factor greater than 0.95, they will not be subject to additional charges.
Addressing harmonic inefficiencies
With traditional AC drives, the only way to reduce harmonic pollution is with expensive and bulky filters which adds cost and complexity to the system. Our AC-to-AC technology mitigates this issue.
At the Sprint Electric HQ in Arundel, Sussex, our team is focused on delivering efficient motor control for our customers. Our regenerative AC drive, Generis, tackles the cause of current harmonics at source and helps to bring the power factor of the installation above the 0.95 threshold.
By converting AC input direct to variable AC output, Generis has a power factor of 0.99 with an ultra-low THD (Total Harmonic Distortion) on input current of less than 4%. It has no DC link circuit and no electrolytic capacitors which cause low frequency harmonics.
By cutting input current THD to ultra-low levels, maintaining a high-power factor, and regenerating braking energy, manufacturers can convert a hidden loss into a measurable saving. The more power a manufacturer consumes, the greater the impact. At 1.5 kW the gain is modest but at higher power levels, the savings have a real impact on operational costs.
Through the use of Generis, a manufacturer can make significant savings, so the capital outlay pays for itself quickly. It reliably delivers dynamic energy savings, avoiding the need to waste energy in braking resistors, resulting in cooler, more reliable equipment, cleaner current waveforms, and lower bills.
