GusD,
Yes from FLC I can read the curve of say a Hitachi Motor and this will give me an indication of the speed.Most Submersible data sheets are calculated data rather than actual data .I have proved this and have been told this by motor manufactures.A true indication is required when a motor is in field ,coupled to the correct size pump,to give the optimin ( best) performance characteristics, at what ever actual voltage and frequency is being supplied (mains or alternator) ( dedicated line or other large equipment on the same grid).
It is surprising how much varation there is between two different brands of motors.
The power authorities and large end users are very selective and particular in maximum performance.
Hence my initial enquiry to the forum.I am enjoying the response.
No , there is not any exposed motor shaft,as the pump housing covers the coupling,and the only way to see if the shaft is free is to lever with a screwdriver usually in the grub screw hole to see if you can turn the shaft.
Ernie is resting now, Regards Gggrover.
alan@downundersubmersibles.com.au
Danfoss has recently introduced a "sensorless" centrifugal pump contoller that consists of a variable frequency drive with special algorithms that enable controlling the flow to within a close tolerance without having to have a sensor mounted to provide flow feedback. It also does NOT require a tach or encoder on the motor.
Does require knowledge of both the pump and the motor characteristics.
I understangd Some VFDs have one feature(DTC)which is direct torque control.This would allow you to run the drive without speed feedback from Encoder or tacho.
Once the drive has the motor finger print it will know what the speed/versus torque should be.
This feature should give you a reasonable accurate RPM
measurement.
