Ever wondered how a motor starter works? Whether you're new to the field or just brushing up, understanding the basics of motor starters can give you a solid foundation in electrical systems—especially if you work with motors daily.
Let’s break it down in a way that’s easy to understand. Think of a motor starter like the gatekeeper for your motor. It controls when the motor turns on or off and protects it from damage. There are two main types of starters: manual starters and electromechanical starters. Both have the same goal—control and protect the motor—but they do it in different ways.
Manual Motor Starters: The Basics
A manual motor starter is exactly what it sounds like—manual. It includes a physical ON/OFF switch or button that someone needs to operate by hand. When you press the ON button, the contacts close, allowing electricity to flow to the motor. Hit OFF, and the contacts open, cutting the power.
Simple, right?
But here’s the catch: manual starters aren’t always the safest choice. If there’s a power outage, a manual starter doesn’t "remember" to stay off. So when the power comes back on, the motor might start running again on its own. This can be dangerous, especially if someone is working nearby or if the motor starts running unexpectedly.
Because of this safety concern—and the fact that manual starters don’t allow for any sort of automatic control—they’re not used in most industrial or commercial applications anymore. Today, electromechanical starters are the preferred choice.
Electromechanical Starters: The Smarter Option
Now let’s talk about how a motor starter works in its more modern form—the electromechanical starter. These are way more common in real-world applications, and for good reason.
An electromechanical starter uses a contactor, which works similarly to a relay. When a control circuit sends voltage (usually a safe 120 volts) to the contactor coil, it creates a magnetic field. That magnetic field pulls the contactor’s internal contacts together, completing the circuit and allowing the motor to draw power—often at much higher voltages like 208V or 460V.
This setup is smart because it separates the control voltage from the power voltage. You can safely control a high-powered motor using a low-voltage switch or automation system.
Protecting the Motor: Enter the Overload Relay
Another key part of how a motor starter works is the overload relay. This component keeps your motor from overheating or drawing too much current, which can cause serious damage over time.
Here’s how it works: when electricity flows through the motor, it creates heat. The overload relay keeps track of that current to monitor how much heat is building up. If something goes wrong—like the motor is pulling more amps than it should, one of the power phases is unbalanced, or the inrush current lasts too long—the overload relay trips.
Once tripped, it de-energizes the contactor coil, which cuts power to the motor and prevents damage. This is a huge advantage over manual starters, which don’t have this built-in protection.
Safety After Power Loss
One of the best features of electromechanical starters is that they don’t automatically restart after a power outage. The contactor will return to its “normal” (open) state, meaning the motor stays off even when power is restored.
But what if your application could pose a safety hazard if the motor restarted automatically? In that case, you can add a start pushbutton to the control circuit. This ensures that someone has to manually restart the motor after power is restored. It also prevents multiple motors or loads from restarting all at once, which can cause dangerous voltage dips or damage to your system.
Motor Starters at National Motor Starters
At National Motor Starters, we know that every job has unique demands. That’s why we offer a complete line of IEC and NEMA enclosed magnetic motor starters, perfect for HVAC technicians, mechanical contractors, electricians, and more.
With over 73,000 different configurations, we can build what you need—fast. Whether you’re looking for a basic starter or a fully customized solution, we’ve got you covered. And thanks to our Quick Ship Program, your starter can be on its way to your job site in no time.
Explore our Quick Ship Options Here.
Final Thoughts
Understanding how a motor starter works can help you make safer, smarter decisions in the field. Whether you’re upgrading outdated equipment or installing a new system, choosing the right starter—and knowing how it protects your motor—makes all the difference.
Got questions or need help finding the right configuration? We're here to help. Because at National Motor Starters, we’re more than a supplier—we’re your partner in power.