Transcript:
[0m:00s] Hey, I’m Mitchell, and welcome to another video in the RSP Education Series. In industrial automation, power isn’t just electricity—it’s the backbone of every control system, motor, and machine in your facility. But why do some systems rely on single-phase power while others demand three-phase? More importantly, what impact does that have on your equipment, efficiency, and maintenance? Single-phase power is everywhere from PLCs and control circuits to small motors and auxiliary systems. However, unlike three-phase power, it doesn’t create a naturally rotating magnetic field. So, how do we make single-phase motors actually spin, and what are the trade-offs? Let’s break it down. Stick around because in part two, we’ll show exactly how we overcome the biggest weakness of single-phase motors. If you like this kind of content and want more educational videos, please like and subscribe. This video is for educational purposes only. Always consult a professional for your application. RSP Supply is not liable for any misuse of this information. With that said, let’s get right into it.
[1m:05s] Single-phase power consists of a single alternating current waveform, typically delivered through two wires: one live or hot wire and one neutral wire. In the U.S., single-phase systems operate at 120 volts or 240 volts, alternating between positive and negative values at 60 hertz. The voltage rises and falls in a single sine wave, meaning power delivery is not constant and drops to zero twice per cycle. Single-phase power is commonly used in residential settings but is also used in industrial automation for smaller-scale equipment such as lighting, small motors, sensors, controllers, and low-power actuators.
[1m:45s] In control systems, single-phase power is used to power devices like PLCs (programmable logic controllers), HMIs (human-machine interfaces), sensors, and relays. These components typically operate at low power levels such as 120 volts, 240 volts, or even 24 volts. Single-phase motors are found in smaller equipment like fans, pumps, and conveyors with lower power requirements. It’s also common in lighting and auxiliary systems across industrial facilities, especially for office lighting or other non-critical systems.
[2m:25s] Now, let’s talk about how single-phase motors work. There’s one big challenge: single-phase motors don’t create a rotating magnetic field on their own like three-phase motors do. A single-phase motor produces power that simply oscillates, going back and forth like a swing moving in one line. This isn’t enough to make the motor spin on its own. To get it started, we use split-phase windings or a capacitor to create a rotating magnetic field. Because a single-phase supply alone cannot produce that rotation, single-phase motors have lower starting torque and a more complex design compared to three-phase motors. To make the motor spin, we need to create a rotating magnetic field, which is achieved with split-phase windings and sometimes capacitors. How exactly we get a single-phase motor to rotate is what we’ll cover in part two of this series.
[3m:30s] Now you know why single-phase power is used in industrial automation, its limitations, and why single-phase motors don’t naturally spin on their own. But we’re not stopping there. In part two, we’ll dive into the fix—split-phase windings and capacitors. We’ll explain how they create a rotating magnetic field, what the role of phase shift is, and why some motors need a capacitor while others don’t. We’ll break it all down step by step so you can understand exactly how single-phase motors overcome their biggest weakness. For hundreds of thousands of other industrial automation products, visit our website for more information and educational videos at rspsupply.com, the internet’s top source for industrial hardware.
