Single-Phase Motor Protection

Thermal Overload Relays are not universally intended to provide single phasing protection for 3 phase motors. Most IEC type overload relays do have an indirect form of 1 phase protection, based on what is called a "differential trip mechanism". This is a balanced spring loadd trip bar that requires equal pressure for each of the 3 current sensing elements to prevent tripping. If current drops significantly on one of the 3 phases, as in a phase loss condition, the balance against the spring is lost and the trip bar moves to trip the contacts, shutting down the starter. But this is not adjustable, not 100% reliable and in many cases, especially if the motor is lightly loaded, may not work at all.

Solid State overload relays now almost all come with true single phasing protection inherently in the design because it is just software. I like those better. Cheaper pones have no adjustability but sometimes have the ability to be turned off, more expensive ones have adjustible settings and maybe even the ability to alarm instead of trip..

Souds to me like you're over-engineering this motor, but, Here's a calculator for the ovld settings. If you don't understand the "potential" relationships enough to wire the relay you should get an electrician "hands-on".

I am inclined to suggest that you wire the overload with all 3 poles in series, and connect to your motor via a suitable-rated line contactor.

The overload setting will then be the FLA rating of the motor.

By wiring all 3 poles in series you will defeat the single-phasing protection.

Now the caveat here is that while I am reasonably sure that I am right about this, there are other experts here who are more experienced than I, one of whom has already posted without telling you what I have just said, and so I wonder if I am correct, or have I overlooked something?