It's possible to use a coil on each phase (ct loop) and monitor the current but I'd advise against it.
Current transformers are not necessary, and they are expensive and bulky too. The Alegro Hall-effect current sensor is inexpensive, small, and responds to AC as well as DC. It is the natural choice for making a go/no-go decision on whether a circuit breaker has tripped.
For this application, AC currents will appear as positive and negative deviations about a baseline output voltage that is one half the DC supply voltage (nominally 5 V) applied to operate the Hall-effect sensor and its signal conditioning electronics inside the Alegro package.
The current to be measured is applied through two pairs of pins on the device that are connected to a low-resistance conductor loop. The loop creates the magnetic field the Hall-effect sensor detects. It is galvanicaly isolated (insulated) from the other pins on the package. Since the power supply is uni-polar, to accommodate AC signals the output will be half the supply voltage for zero current. The output then swings more positive (towards +5 V) or more negative (towards 0 V or power supply common) as the current goes through its AC cycle.
This output swing will then be capacitively coupled to a rectifier and filtered to remove the AC ripple. The resulting filtered DC signal will be proportional to the AC motor current in that phase and can be used as a go/no-go indication that the circuit breaker is open, provided there is current present on at least one of the other two phases. However, if there is no current on any
of the three phases, this could indicate either all three circuit breakers are open, or there is no voltage available on any of the three phases.
To prevent these two "false negative" results, the OP should
add phase-voltage measurements on the input side of the three circuit breakers. I recommend this, along with some means (a push-button switch?) to allow the motor contactor coil to be energized by one of the PICs when all
of the Alegro current sensors are reporting zero current.