Soft starter for 3 phase induction motor using Arduino

Soft starter for 3 phase induction motor using Arduino, this project is designed to make start of three phase induction motor smooth and it avoids motor speed to reach its full speed instantly.  I have already posted a project on soft starter for three phase induction motor using pic microcontroller. Soft starter for 3 phase induction motor is used to control the speed control the current and speed of induction motor at the start. Induction motor draws very high current at the start and motor attains its full speed instantly.  Both these effects induces mechanical jerks in motor at the start and high current induces electrical stress on windings of inductions motor which may damage the induction motor windings.  You may also like to check our other induction motor related projects:

• Variable frequency drive for three phase induction motor
• Variable SVPWM for three phase induction motor
• Soft starter for single phase induction motor
• Thyristor controlled power for single phase induction motor
• Speed control of three phase induction motor using pic microcontroller 

Soft starter for three phase induction motor using Arduino Mega

This power electronics project consists of three main components.  Description of each component is given below:

• Zero crossing detection circuits:  We have used three zero crossing detection circuits. Because we have three phase power supply and we want to control thyristor firing angle for each phase based on zero crossing of each phase of three phase power supply. If you want to know more about zero crossing detection using microcontroller, you can check our zero crossing detection using pic microcontroller article to get better understanding.
• Arduino Mega2560 :  The second most important component of this project is Arduino Mega2560. Arduino is used to read zero crossing signals from zero crossing detection circuits. It also generate and control firing angle to thyristors.  You can read our article on thyristor firing angle control using Arduino to get better understanding about firing angle control circuit.
• Optoisolators : Three optoisolators are used to provided isolation between high voltage and low voltage circuits.  Check this article on optoisoloator interfacing with microcontrollers.

Circuit diagram soft starter for three phase induction motor using Arduino

Circuit diagram shown below contains all the components of this project. I have also explained all the components above.  you can check the video simulation to know about its working.  So now lets talk about the working of this project. As I mentioned earlier, three phase induction motor draws very high current at the start, this high current is also called inrush current.  Also the speed of 3 phase induction motor reaches its full speed instantly which may damage the motor mechanically. So to avoid both these effects soft starter is used. So now lets see how smooth starter works?

Soft starter controlled the magnitude of voltage applied to three phase induction motor at the start. It provides low voltage at the start and after that this applied voltage increased gradually.  This gradual increase in voltage also help the speed of motor to increase gradually instead of reaching its full speed instantly.  Also this gradual increase in voltage, avoid the inrush current of three phase induction motor.  So soft starter solves the issues of high starting current and mechanical jerks to induction motor. For demonstration purpose in Proteus, we have used three lamps instead of three phase induction motor. I have shown in simulation the gradual increase in voltage across all the three phases. For more demonstration, check the video simulation.

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