Please let me know that the theory of AC motor soft starter using TRIAC by ATmega(any).
Some basic points ,hints notes.
imranahmed 
AC Motor Soft Starter using ATmega
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imranahmed ka7ehk
Please specify the kind of AC motor. Universal or synchronous? Single phase, multi-phase, capacitor start?
Jim
Kartman
From my understanding they use phase control. Basically a light dimmer but with coarser control. There's plenty of light dimmer examples using avrs on the interwebs.
With the prices if VSDs tgese days, soft starters are falling out of favour.
imranahmed Motor is induction motor with capacitor start.
Please let me know about VFD?
ka7ehk
VFD = Variable Frequency Drive.
Much used on well water pumps.
Jim
imranahmed Can we build VFD at home?
Kartman
Can you build a vfd at home? With the right tools and talent you can. There has been published projects in electronic magazines such as Silicon Chip (australia). The reality is the cost of parts is nearly as much as buying a complete unit. Atmel and microchip have eval boards and app notes. Unfortunately, some of the components are fairly specialised and hard to get/ expensive.
imranahmed Ok,
Can Induction motor starting torque controller build at home?
Please kindly provide me links ,notes theory.
Kartman
Haven't i given you hints to Google? I mentioned light dimmers.
As for theory - i'm sure you can Google as good as me.
I just Googled "motor soft start theory" . I read the siemens one and they mention a light dimmer as well. So Google for "avr light dimmer"
If it is phase control, then you've got your soft starter.