Intelligent drives cut production costs

Saving energy is one of the biggest challenges we face today and in the future and Lenze is offering it own solution called BlueGreen which looks at savings to be made on machine drives rather than just electric motor efficiency gains

The BlueGreen concept has a deeper meaning for energy saving beyond simple changes. Rather than, for example, change to an energy efficient electric motor with small but worthwhile savings of 2 to 5%, the BlueGreen approach is a holistic one to include the whole machine drive. Typical solutions can include energy saving software for partial loads and the re-use of braking energy. Together these solutions can often yield energy savings in a band 20 to 50%.

Almost half the electric energy produced in the UK is used by industry, and electric drives are responsible for around two thirds of this power consumption. BlueGreen takes a three-pronged approach to evaluate the potential and maximise the possible energy savings, bearing in mind costs and payback times.

The first strategy is to work with machine building customers to use energy intelligently, that is, as little energy as possible. The biggest opportunity in this area is the dimensioning of drives. Too often drives are oversized with safety factors being added ‘just in case’. The result is motors running at partial loads with a disastrous effect on running costs; as much as 20% can easily be lost from the running efficiency. Here the BlueGreen approach is for Lenze engineers to properly evaluate the requirement, using a specialist software tool for complex cases, and dimension the drive so that it runs fully loaded at optimum efficiency. Where the demand on the motor varies, the answer is to use frequency inverters to match the demand. This can give a swift win, with 50% energy savings if the speed is only reduced by 20%, so payback times are short, maintenance is reduced and personal comfort often increased.

The second BlueGreen strategy is to convert electric energy with a high degree of efficiency. A starting point is to use high efficiency motors: the change to using them is gathering momentum with legislation requiring a minimum of IE2 high efficiency by June 2011. Lenze have IE2 motors available, and particularly a wide range of IE2 geared motors with in-line or right angle gearboxes. In some cases dimensions change from IE1 standard efficiency motors, and in every case the electrical characteristics are adjusted. Catalogue data is available to readily evaluate the effects of a change. Also inverters can help with efficient conversion of electrical energy. The new Lenze 8400 motec inverter features VFCeco software that adjusts the magnetisation current of the motor to match the load. This can reduce energy consumption by up to 30%. Lenze has efficient gearbox solutions too. Helical and planetary gearboxes run at around 95 to 98% efficiency depending on ratio. Rather than offer a worm gearbox with typical efficiency in the band 50 to 70%, Lenze offer an energy efficient helical bevel alternative that runs at 94 to 96%. A complete drive package of motor, inverter and gearbox can turn electricity into rotary motion with losses well under 20%.

The third BlueGreen concept is to recover braking energy. Not every machine is suitable for this, but typical cases are hoists, positioning and robotic drives, winding and forming. In the past unwanted energy was dumped to brake resistors where it was dissipated as heat. Lenze has three alternatives to this waste. Where multiple drives are in use, a simple connection of the dc bus allows the energy to be shared, reducing demand on the mains. Particularly for medium to high power, a mains regeneration unit may be appropriate. This is effectively a drive that runs in reverse turning generated dc current into ac current that goes back into the mains. The third option is capacitor storage, an effective solution for fast cycling drives.

TheLenze BlueGreen solutions are a range of options that can be adapted to different types of machines and different user profiles. On the one hand, upgrading from a 11kW IE1 standard efficiency motor to one with IE2 high efficiency might save 2%, or 4% by going to IE3 premium efficiency. Lenze claims that by using its BlueGreen know-how savings of 20% are a conservative estimate and figures of 50% are not unknown.

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