Re: bimetal OLs and "Phase Loss Sensitivity". I had to study this as the PM for a mfr a few years ago.
It used to be that the IEC control mfrs sold these standard adjustable bimetal OLRs as having "Phase Loss Protection", but they had to change the wording to "...Sensitivity" because it doesn't really detect a phase loss. What they do is use a compensating spring loaded mechanism, sometimes called a "differential bar" inside that will BIAS the trip point if you lose a phase. What happens is, if current is flowing on each phase, the bimetal stips are applying relatively equal force to the trip bar. The differential bar is applying an equal counter force. This by the way is why you must loop power back through the unused phase on a single phase application on these types of OLRs.
If you lose a phase, the differential bar is now stronger than the force exerted by the remaining 2 bimetal strips, and the trip point is effectively shifted to be lower than it was. In other words the remaining 2 bimetal strips now have to move the trip bar LESS to trip because the differential bar already moved it part way. The PURPOSE behind this was because if a motor is single phased, there are negative sequence currents inside the rotor that are causing additional heating in excess of the thermal model the bimetal strips were selected for. So it takes LESS current under a single phase condition to overheat the motor than if all 3 phases were there. So this differential trip compensation bias to make the trip point lower, compensates for that increased heating effect.
But here's the problem. If the LOAD on the motor is light enough, these bimetal trips may never trip on a single phase situation, because even though it is biased lower, it might still be below the threshold of the trip curve. In most cases this is not an immediate problem because if it's lower, it's lower and no harm no foul. But there is a tolerance issue that allows some motors to burn up anyway, especially unattended applications where the motor runs for a long long time like this. So they had to start using the term 'sensitivity" instead of "protection" because it is NOT true phase loss protection, it is protection against one of the worst EFFECTS of phase loss.
SSOLs are different, what they do now is digitally monitor current. If the current on any one phase is below a setpoint, it trips; plain and simple. For most of the mfrs, that threshold is 20% of the setting. Unfortunately for Sq. D, their Motorlogic unit is factory set for 30% and they have troubles with it nuisance tripping, especially on pump systems where the current builds up slowly as the flow increases. For that reason, they started selling an OPTIONAL version that has a 20% threshold or can be defeated. I don't know of any other SSOL that has that problem.
I happen to know that A-B now gives you SSOLs if you don't ask, because they are essentially the same price and you don't have to mess with the heater element selection any longer. You won't get the superdy duper one that talks to everything else if you don't ask, but the one you get (E1+) will have Phase Loss Trip as I described above.
.