Circuit Clarification

[electronicsLearner77]

What does the below circuit represent

I have not shown the complete circuit, but V_M1, V_M2, V_M3 are motor voltages, what information does REC_NEUTR give?

 

[Harald Kapp]

V_M1, V_M2, V_M3 are motor voltages

Which motor voltages? DC, AC 3-phase?
I assume it is AC 3-phase. Then the 3 resistors will add the voltages up to form the arithmetic mean of the 3 phases.
If all is well, this summ is 0 V:

= 0
By measuring this voltage on REC_NEUTR one can determine the "health" of these voltages. If the sum is <> 0 V, something may be wrong.

 

[Bluejets]

3 phase motor an never be perfect as in practice there is always some imbalance.

 

[electronicsLearner77]

3 phase motor an never be perfect as in practice there is always some imbalance.

Is there any threshold value beyond which we can say it is invalid?

 

[Harald Kapp]

That will depend on the application. The circuit measures the voltages, which are supplied by the power company as a 3 phase system or are supplied by a 3 phase motor controller. Measuring these voltages will not give a direct indication of the state of the motor. You can measure them even without a motor attached. But due to the impedances of wiring you will see changes in the voltages when a motor is connected and has a failure, e.g. a short circuit in one of the windings, which un turn will cause the voltage to drop.

What this circuit really does and which thresholds are possibly used in monitoring is impossible to say without knowledge of the rest of the circuit, Better yet: read the description from where you took that circuit.