[Help] Questions about the component PC817 in schematic

[sfiga69]

Questions about the component PC817:
In your opinion, what could be the possible need of this optocoupler?

The schematic covers the power control of an induction motor, controlled by a microprocessor.
If anyone can suggest some ideas .... I appreciate it.

Thanks to all

[MoarK]

When the motor is running it should cause pulses on the opto-transistor.
Perhaps it is meant to be used for an indicator light to show motor is running?

[sfiga69]

TNX MoarK,

Could be a signal to monitor the operation of the engine.
But, in your opinion, could also be used to detect zero cross of AC when the engine is running to sync trigger triac?

[MoarK]

Isn't that what a triac does anyway?

[sfiga69]

Hi MoarK,
I meant that the signal from the PC817 is used by micro to synchronize a trigger of the triac, at zero crossing of the sinusoid.
Could it be?

[pickit2]

I have seen this in a panasonic microwave oven and it monitors that that AC voltage is there for the inverter. ie: the fuse and the voltage for inverter is good. one of the faults in the ciruit is the diode across the opto goes short ciruit. over 70% of failed pcb's have this shorted diode.