Therefore it's a reactive load. It may cause AC voltage crossings to be out of alignment with AC current crossings. Then you're not certain which you are sensing.
Or it may cause continued current flow through the triac, causing it to stay On after it's supposed to turn off.
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To detect zero current crossings, it does not necessarily work properly if you sense voltage across a capacitor or inductor.
Instead sense voltage across an ohmic resistance (low ohm value, low enough to create a usable reading).
Thank you very much to join in this thread.
You said well, for the inductive load PF is less then 1. Phase between V & I makes problem during zero crossing. Manufacturers said, not to use a "zero crossing type". Random type fits well.
Any way, if you look this circuit, a monostable 555 timer is used to make pulse train with certain frequency. MOC3021 has isolation between primary and secondary. That means this circuit is not usefull for zero crossing detection, but zero crossing can be done here.
Now if I fix the ON time and OFF time of 5 v pulse with proper duty cycle, cant it be possible to see in scopes ? Can we compare pulse and full AC 1 cycle in load? May be not!
MOC3021 pin 4 gate pulse will decide when the TRIAC will turned ON. There is " holding time" and voltage ON state. Not sure what it tells about zero current and zero voltage switching.
Sometime TRIAC may not turned ON. Gate current and dv/dt facts here.
Most of the people use microcontrollers to make particular pulse width and firing angle for zerocrossing.
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My case it capacitive load.
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Sure, may be its dedicated to zero crossing.