What is a soft starter
The soft starter is a particular kind of motor starter that lowers the voltage while the motor is beginning by using the voltage reduction approach.
During motor startup, the soft starter gives a progressive increase in voltage. This will enable the motor to gradually pick up speed and accelerate. It stops any mechanical tearing or jerking brought on by an abrupt supply of full voltage.
How it works
The number of anti-parallel linked thyristors is contained in Soft Starter. Thyristors are present in pairs for each phase.
A thyristor is a semiconductor device that is typically isolated, but when a firing signal is applied to the gate, they begin to conduct and permit the passage of current and voltage.
Thyristors are fired at the appropriate time to accomplish soft beginning, only allowing the final half of each sinusoidal voltage pulse to pass through them.
Additionally, after the firing signal is sent, it is sent earlier and earlier so that a larger and larger portion of the voltage wave can travel through the thyristor.
Eventually, a firing signal is sent after each time a zero is crossed, allowing the thyristor to accept 100% of the voltage.
The opposite is done when stopping.
The firing signal is delivered later and later as the stop initiates, allowing less and less of the voltage to flow through until the end voltage is achieved. Initially, the full voltage is allowed to pass through the thyristors. The motor then stops when no more voltage is provided to it.
Start: The thyristor initially permits a little amount of voltage through it before ramping up in accordance with the starting ramp-up time.
Stop: The thyristor is fully conducting when the soft stop starts, and the voltage falls as the ramp time for the stop is set.
Starting results in lower voltage, which causes current and torque to fall as well.
The current will be reduced to roughly 50% of the maximum current at that speed and the torque will be reduced to around 25% of the maximum torque if the voltage is reduced to 50% of the full voltage.
Advantages
Improved Efficiency: Due to the low on-state voltage, softstarter systems with solid-state switches operate more efficiently.
Controlled startup: A major benefit of the soft starter is that the starting voltage can be readily changed to control the starting current, ensuring a smooth start of the motor without any jerks.
Acceleration under control: A soft starter is used to gradually manage motor acceleration.
Solid-state switches are used to achieve low cost and small size.
Circuit
Test and Results
The device was tested in a 1HP motor and following results were observed
Get the detailed circuit, PCB file, code on my GitHub page
https://github.com/ELDHO-KURIAN/DIY-AC-PHASE-ANGLE-CONTROLLED-SOFT-STARTER