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Back to basics

Vacon’s unique variable-speed AC drives are highly efficient, reliable, and easy to run, and offer valuable savings in energy usage and overall costs. Unlike almost all its competitors, Vacon focuses entirely on these types of drives, which are supplied in the 0.2 kW to 5 MW range.

It may surprise many people to realise that electrical motor systems account for by far the largest single usage of electricity – over half.

Studies have shown that some 90 TWh/a of the 707 TWh/a expected to be consumed in Europe in 2015 could be saved through the use of high-efficiency motors and drives. Replacing standard motors with high-efficiency units could save about 35 TWh, while using drives could save about 56 TWh – equivalent to a reduction of about 36 million tonnes of CO2 emissions.

Drives, therefore, offer a much higher energy-saving potential, due to the fact that only the energy needed by a process is used and no extra energy is required for control mechanisms.

Savings all the way

AC drives, like those developed and supplied by Vacon, control the speed of either an induction motor or a synchronous motor by adjusting the frequency and voltage of the power supplied to the motor. Varying the speed in this way, rather than running motors at a constant speed, enables processes to be controlled very precisely and saves energy.

Fans and pumps are the most common area where this can be a benefit, as systems are usually oversized to cope with rare  extreme situations. Replacing a fixed-speed with a drive can save 10-30% of the energy that would otherwise be needed without impacting process performance.

When full load is not required, even a small drop in speed can yield major energy savings. A ventilation system running at 90% load, powered by a Vacon drive, for example, requires only 73% of the energy required by a fixed-speed solution.

This can be particularly useful in smaller, stand-alone systems on board ships and drilling rigs, where AC drives can save substantial amount of diesel fuel. As AC drives use only active power, generators do not need to generate reactive power, which imposes less load on them.

Given the fact that so much electricity is used in motors, it pays to optimise the efficiency of these systems by using drives and high-efficiency motors.

Replacing hydraulic control systems with AC drives can reduce fuel consumption by tens of percent. Modern, active front-end technology reduces the oversizing otherwise needed for transformers and generators, giving additional savings in term of fuel, weight, and cost.

Excellence through modularity

The key feature of all Vacon variable-speed AC drives is their complete hardware and software modularity, which is unique in the field. Three different control units, air or liquid cooling options, and up to five different I/O cards and field-installable conversion kits can be ‘mixed and matched’ very flexibly.

Vacon NXS control units cover applications that do not require the precision provided by a feedback device, while Vacon NXP units can incorporate encoder feedback to deliver ultimate performance – and both can be detached from power units and mounted elsewhere.

> Michael Björkman
(Published in HighTech Finland 2008)