Variable Frequency Drives are increasingly becoming the necessary element of most industrial processes of the day. While machineries use drives as more of an automation rendering device delivering benifits as productivity rise through increased production, industrial processes use drives as energy saving devices, allowing their machines to run only as demanded by the process and slowing them down otherwise.
Drives are a simple construction, an AC to DC rectifier, a DC bus and a DC to AC invertor. The rectifiers are circuits made of semiconductor devices that are controlled through electronic circuits that can regulate the voltage or the current through switching or other such similar methods.
The matter of concern is that the annual sales of Drives in India is growing steadily at a rate of more than 11% consistently for the last 3 years. Now it turns out that 80% of these drives are with six pulse rectifiers . Six pulse rectifiers introduce 30-40% current harmonics into the AC networks from which they draw power.
This means that the percentage increase in the Harmonic content of current in networks is growing at such a vast pace that one will very soon encounter a situation that the huge pollution in networks will call for a costly oversizing , resulting a countereffect of the savings done on energy front.
A unique condition, where saving energy can get costlier than not saving it.
Worth a thought eh?
1 comment:
Before arriving at any sort of conclusion, we need to check what is the losses generated by harmonics in comparison to the total wattage of the network. I believe the standards set by IEEE519 or the Brit G5/4 have considered these into consideration.
Secondly the energy saving of the drive is known to approximately (minimum) 20 percent. Surely harmonics would not have caused that much loss.
What do you say, people?
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