Masoud85
Newbie level 4
![Newbie level 4](/styles/images/ranks/blevel1.gif)
Hello dear friends
I'm designing a soft starter circuit for inductive loads specially single phase motors.
I've used an AVR microcontroller and mains zero crossing detector and a Triac.
As we know from power electronics references the fire angle in inductive loads can not be smaller than phase angle of load.
If phase angle is ɸ and fire angle is α then ɸ<α<π . So if α=ɸ voltage and current of load is sinusoidal and load gets maximum power.
My question is how can we determine phase angle of unknown inductive load? Because users maybe connect an asynchronous squirrel-cage motor or maybe a universal vacuum cleaner motor to the soft starter. Both of them are inductive loads but with different phase angles!
Is it necessary that i use a current transformer to detect load current zero crossing and after first fire pulse applied to triac calculate phase angle of load? if yes how can i calculate it?
Thanks
I'm designing a soft starter circuit for inductive loads specially single phase motors.
I've used an AVR microcontroller and mains zero crossing detector and a Triac.
As we know from power electronics references the fire angle in inductive loads can not be smaller than phase angle of load.
If phase angle is ɸ and fire angle is α then ɸ<α<π . So if α=ɸ voltage and current of load is sinusoidal and load gets maximum power.
My question is how can we determine phase angle of unknown inductive load? Because users maybe connect an asynchronous squirrel-cage motor or maybe a universal vacuum cleaner motor to the soft starter. Both of them are inductive loads but with different phase angles!
Is it necessary that i use a current transformer to detect load current zero crossing and after first fire pulse applied to triac calculate phase angle of load? if yes how can i calculate it?
Thanks