Practical Uses of Variable Speed Drives

6th June 2013 | Posted by Charlotte Miskell

Here at Proplas International we are dedicated to helping our clients become more efficient, and streamline process wherever we can.  We have built up quite a reputation for doing just that, and one of the projects we were instrumental on last year caught the attention of Rockwell Automation.  Our customer was Europe’s leading supplier of rigid plastic packaging, where we focused on the PET bottle and jar moulding machines, installing variable speed drives with a resultant reduction of 27% for energy consumption.


Being a recognised leader in saving energy with a focus on injection moulding machines, we were able to alternate the preset operating speeds by installing variable speed drives to ensure that the process was capable of meeting the maximum hydraulic demand (when the moulds open and close), whilst lowering speeds during reduced demand.  To meet this demand, a single inverter was installed on each machine and then linked to a micro Programme Logic Control (PLC) to offer simple sequencing logic.


Our director Stephen Anderson explained how the process was set up, noting that the process was controlled by hydraulic pumps which ran at a constantly high speed to accommodate for the maximum demand.  “This was an inefficient process, since the energy usage remains constant (and high) while the actual power demand varies.”


PLC Programming Potential with Proplas

Keen to involve our customers in every step of the process Stephen continues, “We performed a number of tests with the company to demonstrate the potential, and convinced them that there could be major energy reductions and associated cost savings.  As a result, we were asked to retrofit a drives solution [which included a PLC programming unit] to 13 of the company’s injection stretch-blow-mould machines.”


The ultimate result is quite staggering: a reduction in power usage from 40kW to 11kW for each machine courtesy of the variable speed drives.  This saves the customer an estimated £5500 on each machine, with the total payback time being a swift 14 months.


The whole article by Rockwell Automation is available to view here.


If you would like to find out what efficiency savings Proplas International could make for your business, or if you wish to chat about installing a variable speed drive then contact us online or by calling 01282 872 450 to discuss your requirements.

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