Transcript:
[0m:00s] Hey, I'm Mitchell, and welcome to another video in the RSP Education Series. Today, we're going to talk about soft starters. A soft starter reduces the inrush current when a motor starts and minimizes mechanical stress on your equipment. Imagine driving a car, rather than flooring the gas pedal as soon as you start, you press it gently, allowing the car to pick up speed gradually. A soft starter does the same thing for electric motors by slowly increasing power so the motor doesn’t start with a sudden surge. This reduces stress on the motor and the electrical system, helping everything last longer and run smoother. This video is the first in a progressive series that will take you from the basics of soft starters to the cutting-edge technology shaping the future of motor control. Whether you're an engineer, technician, or just curious about industrial automation systems, you're in the right place. If you like this content and want more educational videos, please like and subscribe. This video is for educational purposes only. Always consult a professional for your specific application. RSP Supply is not liable for any misuse of this information.
[1m:00s] So, what are soft starters? They’re devices used to reduce inrush current and torque during motor startup. By controlling the voltage supplied to the motor, they allow a smooth ramp-up to full speed, reducing mechanical and electrical stress. The purpose of a soft start is to ensure smoother operation and protect connected components. Let’s go over the basic functions of a soft starter. Gradual voltage ramp means the voltage is slowly increased to provide a controlled startup. Current limiting helps reduce the high inrush current that occurs when motors start suddenly, protecting your electrical system and improving reliability. They also enhance system efficiency by reducing wear and tear on belts, couplings, and gears, which in turn lowers maintenance needs.
[2m:10s] A common alternative to a soft starter is a direct-on-line starter, or DOL. These two devices differ significantly. A soft starter gradually increases voltage, while a DOL starter applies full voltage instantly. That instant voltage creates inrush current, also known as starting current, which can be six to eight times higher than the normal operating current. This surge causes stress on motor windings, voltage drops in the electrical network, and mechanical strain on connected parts like belts and pulleys. Soft starters, on the other hand, limit inrush current to about one and a half to three times the full load current by carefully controlling voltage and current during startup.
[3m:20s] Torque control is another major difference. With a standard starter, the motor hits full torque almost instantly, which can create abrupt mechanical forces. For some applications like crushers or compressors, this might be acceptable, but for others, such as pumps, conveyors, or fans, a soft starter is the better option. It allows you to customize the ramp-up time for smoother acceleration. The result is lower motor stress, less wear on mechanical components, and overall improved reliability. While soft starters come with a higher upfront cost due to their advanced electronic control, they save money in the long term through lower maintenance and reduced system strain.
[4m:10s] You’ll find soft starters used in industries and applications where motors need controlled startups. Pumps, for example, benefit because soft starters help prevent water hammer or pipe stress from sudden changes in flow. In conveyors, they reduce mechanical shock to belts and equipment, especially in packaging lines or food processing facilities handling delicate products like glass bottles or eggs. Standard starters are better suited for smaller compressors, machine tools, or basic agricultural equipment, where quick starts and low torque demands make simplicity more practical. In smaller irrigation systems, for example, standard starters work fine without the added control a soft starter provides.
[5m:10s] The bottom line is to use a soft starter when you need to reduce mechanical stress, prevent electrical surges, or optimize startup control for high-torque loads. That wraps up our introduction to soft starters, but there’s much more to explore. In upcoming videos, we’ll break down key components such as power circuits, control circuits, and bypass contactors, and show you how they all work together. We’ll also cover real-world applications, troubleshooting, diagnostics, and advanced setup techniques like configuring ramp-up and ramp-down times. For a full line of soft starters and hundreds of thousands of other industrial automation products, visit RSPSupply.com the internet’s top source for industrial hardware and education.
