Energy saving on drilling machine

The drilling machine started and stopped by 2-3 minutes. It drilled and removed the drilling tool. Using motor speed drive the energy saving appeared, because there was soft start and no inrush current. In 24 hour this was enormous saving. At the oil pump, which used these machines, the regulation of pressure worked by bypass valves.  I closed the bypass valve and regulated the oil pressure by motor speed driver too. I installed a small measuring system, it was Power Logic software and PM810 devices of Schneider Electric. I measured the energy for 2 weeks with speed driver and without speed driver. The result was, the price of installing variable speed drive come back in less than 1 year. This was a car factory. They installed speed drives in first step to 20-25 machines.

The best results (in terms of economic cost) occur when the duty cycle requires variable torque.

But also remember - you need to be looking at ALL the parts in the various alternative systems. The input (energy in) comes from the electric utility line. The output (energy out / work done) is after the actual mechanical pressing action (i.e. you have a finished product).

That means checking losses for transformers, cabling, power electronics (including drives), rotating machines (including external excitation, if required), gearing, mechanical device (driven equipment), and so on ... for EACH operating point in the duty cycle.

Different devices will have - for the most part - different efficiency characteristics as the load varies from zero to full (to potential overload). Try to use information that is as accurate as possible for each device at each point ... that way you have the truest comparison.