I'm working on a submerged pump application, running on 415V three-phase. I don't know for sure, but I believe the pumps are only a few KW.
The customer is saying that the pumps run fine when the site is on mains power; but when it switches to generator, my motor protection unit trips the pump on Low Power Factor. I’ve asked for the motor protection unit logs but haven’t seen them yet, so that’s all I have to go on. The Low Power Factor threshold should be set to 0.5, but again I can't be sure.
If the generator rotation was incorrect, then the phase fail relay and the motor protection unit should both have tripped, preventing the pumps from running.
If the generator voltage was higher / lower than the mains, then the current would be lower/higher, but the inductance of the motor hasn’t changed so why would the phase shift be different?
I’ve asked a few experienced engineers here, but no-one has any suggestions as to what is going on.
Any suggestions? Thanks for your help!
Edit per request from @Transistor - I'm not sure that the schematics will add anything more than what's described above, it's a simple system. The schematic editor looks Ok for electronics, but not for electrical so I've pulled some wiring diagrams from other sites. These are example schematics from a typical site:
Simple DOL Starters. Ignore the reversing contactors, they're not present at this site (and the Low PF fault is ignored when reversing anyway).