Understanding the differences between a contactor and a relay is critical when working in the electrical industry. Application, function, and current determines which one should be used to avoid circuit overload. Let’s discuss what each is and how they differ.
What Is a Relay?
Relays are electrical switches used to convert small electrical inputs into higher currents using electromagnetism.
They work as an amplifier or a switch, depending on the application needed. They’re simply one circuit powering another circuit. Relays are quite versatile and work well with both complex and simple circuits.
What Is a Contactor?
A contactor is a switch which is controlled electrically and is used to switch electrical powered circuits on and off. It’s actually considered a type of relay, but the contactor is able to operate at much higher currents than a relay.
How Do Relays and Contactors Differ?
The main difference between a contactor and a relay is the current. Relays handle a lower current (10 amps or less) while contactors can handle a higher current (10 amps or more). Still, there are a few more important differences to be aware of beyond load capacity.
Contactors have more safety features than relays because they carry higher currents. They include spring-loaded contacts, arc suppression, and overloads.
- Spring-loaded contacts prevent the welding together of high-load contacts. The spring-load ensures both circuits break at the same time in those situations.
- Arc suppression allows the extension of a path that an arc needs to travel. An arc is suppressed when energy can’t overcome the extension.
- An overload interrupts a circuit when a current exceeds its threshold beyond a safe amount of time.
A relay is most commonly used in a single-phase application and a contactor is for three-phase applications.
In other words, a contactor joins two poles together with no common circuit between them. A relay, however, uses one common contact connecting to a neutral position.
How To Choose Between a Relay or Contactor
As you can see, the differences between a contactor and a relay are significant and choosing between the two does matter.
For 10 amps or less current and up to 250VAC (volts, alternating current), and a single-phase, a relay may be used.
When working with 9 amps or more and up to 1000 VAC, along with one to three phases, a contactor must be used instead of a relay.
Always consult a licensed electrician concerning contactor and relay needs.
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