Motor mounting position

Well first off we are talking about a cheap Chinese $265 7.5kw (10hp) VFD. My calculations said 2500psi @ .96in^3 was 10hp. I think where the diffrence between the RPC and VFD are aperant is in the service factor of the motor. The motor has a 1.15 SF which means you can run it up to 11.5hp, not consistently but it’s there if you need it. This being said I don’t think the VFD was providing even the stated 7.5kw it was rated for. It’s hard to describe the diffrence but the press motor sounds different. When running off the VFD it was fine but seamd to kinda bog down once the pressure started to climb. Kinda like it was alowing the motor the slip. I actually had it just straight up trip the VFD, and not even under full load. It would happen when I was cycling the ram up and down real quickly. But the funny thing is this and I don’t know what it tells up but it’s somthing. Befor the VFD popped I was messing with the pressure settings. Slowly increasing it to see where the tripping point was. It was funny because I was not able to trip the VFD at this time. But over 2700psi the motor would completely stall. Also max pressure buildup was slower once it hit 2000psi. So I left the press set at 2700psi. Fast forward to the RPC and the same pressure settings as I never changed them. And the pressure shoots right up to 3000psi and the moter does not bat an eye at it. No stalling or even a change in sound..
 
Thanks for the explanation - makes sense. Why are we surprised when a Chinese VFD doesn't put out the rated power? Perhaps that's why my 3hp VFD has always worked so well with my 2hp motor? Also, there is VERY seldom I've pulled the full 2hp from the motor on my grinder.
Ken H>
 
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