Our job was to find a way to save energy of an ELGi Compressor at Minerals India site in Ranchi. The operation of the existing system was as follows:
The ELGi compressor was using star-delta starter to start a 15 KW AC Motor and starting current is very high in a star-delta. The compressor was attaching itself whenever the pressure in the tank goes below lower limit and detaching itself when it reaches the desired upper pressure limit, and during the whole time the motor is running at full speed with 12amp current. Every time the compressor attaches itself the motor takes up huge current. Hence overall energy consumption was huge.
We provided a solution with a VFD and connected it to the controller of the ELGi compressor. The VFD is running in PID loop and there is no peak starting current as there is an acceleration time. Now the VFD is running at very low speed (Keeping in mind that the compressor’s minimum speed should not go below 40% of its rated speed) to maintain the pressure, no need of high speed which was happening before without VFD. The maximum current taken for most of the time is 10 amp with full load, where as before without VFD at full load the current was 25 amp.