what makes you think there is power being supplied to the motor?
if you measure the voltage on the output of a solid state device like that with a high impedance meter you will probably see whatever the line voltage is because the meter impedance is much higher than the solid state device.
many soft starts only have solid state devices on 2 of the 3 legs anyway.
most soft starts have a bypass contactor that turns on once the motor is up to speed. it is far more efficient that way and allows for much less expensive solid state components.
I agree. If you use a digital multi-meter, it will read the leakage current through the RC Snubbers that protect the SCRs. It's only going to be 1-2mA of current and if you measured it with an old analog meter the meter burden drives it down to zero V, but the DMM presents almost no load so it reads close to the line voltage potential right through it. The snubbers are just a small resistor and a capacitor in series, connected in parallel to the pair of SCRs in each pole. This is what it looks like (except without the inductor on the output side).
There are (unfortunately) cheap soft starters out there that only put SCRs on 2 of the 3 phases, which makes this even worse in that if any
ONE SCR shorts, there is no way to stop current flowing to the motor. In a full 6 SCR design, it takes at least two shorted SCRs in separate phases for that to happen. That unit from SAF is not one of those, it has all 6 SCRs. But if you are using an analog meter and still reading a voltage across from L1 to T2 for example, then you may have multiple shorted SCRs. It can happen.
That particular soft starter DOES have integral bypass contacts. It's not a "contactor" in the conventional sense, each individual pole has its own separate 1 pole contactor that shorts out the SCRs when it is done ramping. It could therefor be that one of those contacts is welded closed, you would not be able to tell the difference between that or a shorted SCR. BUT, the soft starter has a detection circuit inside that would give you a fault light warning you that you have an SCR shorted. That light only comes on when you turn the motor OFF, and the voltage drop that should normally be there across the SCRs is not there. If you don't have that light, I doubt there is anything wrong.
If you really want to know if the SCRs are shorted, disconnect power and the load, then read the resistance across each pole. Less than 10ohms of resistance and there is a shorted SCR in that pole. Doesn't matter which one, you will need to replace them all if even one is shorted (in my professional opinion) because whatever took out one also came close to taking out the rest, but once the first one (or two) failed, that prevented the rest of them from shorting. They will however "catch up" in short order.