A few other differences that may be important, depending on the application: 1) The poles of a multi-pole relay are not guaranteed to all be in the same state. This is because each pole is mechanically independent of all others. In a contactor, all poles are mechanically linked and, therefore, are guaranteed to all be in the same state. In a relay, one pole could be welded closed while the others are free to move. This guaranteed simultaneous state change is critical in safety and motor starting applications where one pole "disagreeing" with the others could have catastrophic results. 2) Most industrial contactors have the ability to add auxiliary contacts that also have the same guaranteed state change characteristics as the primary contacts. These aux contacts are typically used for signaling the state of primary contacts and come in both normally open and normally closed as well as combinations thereof. 3) "Forcibly guided" relays have the same state change characteristics of relays but are not rated for high current. They are relatively rare and are typically only used in safety applications. 4) Contactors are rated, in the US, two ways, depending on how the contactor is going to be used. First is by "general" use, meaning non-motor loads, and is expressed in Amps. Second is by horsepower and voltage when the switched device is a motor. The reason for this is that a motor has a high inrush current that quickly subsides once the motor is turning, as opposed to a constant current load. For example, a contactor may be rated at 7.5 HP @ 480VAC (11 full load amps) AND rated for 28A general use. The distinction can be very important, depending on the application. Great intro video and my apologies for nerding out! As a controls engineer with some green junior engineers under me, I cover this stuff every day.
Joe that was an excellent demonstration, thanks my friend 👍😁
Thanks Dave 😄
A few other differences that may be important, depending on the application:
1) The poles of a multi-pole relay are not guaranteed to all be in the same state. This is because each pole is mechanically independent of all others. In a contactor, all poles are mechanically linked and, therefore, are guaranteed to all be in the same state. In a relay, one pole could be welded closed while the others are free to move. This guaranteed simultaneous state change is critical in safety and motor starting applications where one pole "disagreeing" with the others could have catastrophic results.
2) Most industrial contactors have the ability to add auxiliary contacts that also have the same guaranteed state change characteristics as the primary contacts. These aux contacts are typically used for signaling the state of primary contacts and come in both normally open and normally closed as well as combinations thereof.
3) "Forcibly guided" relays have the same state change characteristics of relays but are not rated for high current. They are relatively rare and are typically only used in safety applications.
4) Contactors are rated, in the US, two ways, depending on how the contactor is going to be used. First is by "general" use, meaning non-motor loads, and is expressed in Amps. Second is by horsepower and voltage when the switched device is a motor. The reason for this is that a motor has a high inrush current that quickly subsides once the motor is turning, as opposed to a constant current load. For example, a contactor may be rated at 7.5 HP @ 480VAC (11 full load amps) AND rated for 28A general use. The distinction can be very important, depending on the application.
Great intro video and my apologies for nerding out! As a controls engineer with some green junior engineers under me, I cover this stuff every day.
No Problem, Thanks for adding some great info, I have never worked with industrial components.
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