Have a new test stand being set . It will have 480v 150 hp motor on it . My boss wants to install a VFD to drive this . The manager of the department says its not a good idea to VARY THE RPM's OF A PISTON PUMP . I'm not a pump person just wondering if that is true !
If you look at the literature on a HYDRAULIC piston pump, you will find minimum and maximum recommended speeds. We've never had problems varying, via VFDs, speeds between these.
But ... unlike centrifugal pumps, at a given displacement a piston pump shaft torque is dependent on pressure, that is, the torque at 600 rpm and 3000 psi is the same as at 1800 rpm and 3000 psi. Be certain your drive is capable of providing the appropriate currents.
Having said that, I've operated fixed displacement piston pumps over a 10:1 range with no trouble. When I asked the manufacturer why he used 600 rpm as his minimum, the response is that no one uses motors of more than 12 poles ... and that their efficiency ratings would not look good at lower speeds, but there would be no damage of any type to worry about.
Positive pressure on the inlet is smart to ensure "priming" is not necessary. The air performance is not good <g> at 30 rpm, so the 30 inches above oil level we use at 1200 and 1800 may be a problem.
