jraef
Member
OK, that's valid, except the pump itself represents SOME load, as opposed to an uncoupled motor. And for this, all you need to do is run it unloaded, measure than value, and set up a detection method using that value as a trigger. It doesn't really matter what that value is as a percent of motor FLC. But to be honest, a BETTER way to do that is to use a device that measures WATTS, it's more exact with regard to actual shaft power. Lots of "smart overloads" now offer this as an option, I use it extensively.Alternate method to detect cavitation or empty inlet/sump, possibly preferable to adding a level switch?
One thing I have been doing with this is to monitor the motor shaft kW with the OL relay, then compare that to a pump flow transducer signal. Flow and kW should track together consistently, so I want to see if they start to diverge. If the kW increases disproportionately to the flow, that means bearings are wearing out. If the kW decreases disproportionately to flow, there is cavitation, blockage or air getting into the system. Either way, I want to know about it.