A soft starter is an electronic device used to gradually ramp up the voltage and current supplied to an electric motor during its startup phase. Its primary purpose is to reduce the mechanical stress and wear that can occur when a motor starts abruptly at full voltage. Here's how a soft starter helps in achieving this:
Voltage Ramp-up: Unlike a direct-on-line (DOL) starter where the motor is subjected to the full supply voltage from the start, a soft starter employs a controlled ramp-up of voltage. It starts the motor at a lower voltage and then gradually increases the voltage over a preset period of time. This gradual acceleration reduces the initial torque and the associated mechanical stress on the motor and connected mechanical components.
Current Limitation: When a motor starts, it draws a high current due to the initial load inertia and the impedance of the motor windings. This high inrush current can cause voltage dips in the power supply system and lead to mechanical stress on the motor shaft and connected equipment. A soft starter limits the starting current by controlling the rate at which the voltage is increased, thereby reducing the mechanical shock to the system.
Reduced Vibrations and Jerks: Abrupt motor starts can result in rapid changes in speed and torque, leading to vibrations and jerks in the mechanical system. These vibrations can wear down bearings, couplings, and other moving parts. By providing a smooth and controlled acceleration, a soft starter minimizes these vibrations and ensures a more gradual transition to full speed.
Reduced Belt and Gear Wear: In systems that use belts, gears, or other transmission mechanisms, sudden starts can cause these components to experience shock loads. A soft starter's gradual acceleration prevents sudden torque spikes, which helps extend the lifespan of these components by reducing wear and fatigue.
Extended Motor Life: The reduced mechanical stress and wear on the motor and connected equipment result in an extended operational lifespan for these components. This can lead to cost savings through reduced maintenance and replacement requirements.
Energy Savings: Soft starters can also contribute to energy savings by preventing the excessive current draw that occurs during direct-on-line starts. By limiting the starting current, soft starters help in avoiding peak demand charges and reducing overall energy consumption.
In summary, a soft starter aids in reducing mechanical stress and wear during motor starting by controlling the voltage and current supplied to the motor. This controlled acceleration minimizes the impact on the motor and connected components, leading to smoother operation, increased equipment lifespan, and potential energy savings.