Simulink Of Soft Starter Control Circuit

[doinfinity]

Hi all,

 

I have designed a control circuit for single phase soft starter and its setting as below:

 

Basic control circuit:

http://i71.photobucket.com/albums/i156/doinfinity/1phase-1.jpg

 

Setting:

http://i71.photobucket.com/albums/i156/doinfinity/setting.jpg

 

Vrms output:

http://i71.photobucket.com/albums/i156/doinfinity/softstart_vrms_output.jpg

 

I wonder why there is stair shaped appeared on the Vrms output. As I use a linearly increasing ramp compare with the triangular waveform, why the Vrms output is not linearly increasing before reaching full voltage?

 

Is this circuit consider as a soft starter? and any further improvement i can make on this circuit?

 

Thank you for your help.