What is the difference between an overload protector and a thermal relay for circuit protection?
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I have a question for everyone: 1. Does a circuit breaker only provide short-circuit protection? Is there automatic cut-off protection against overload (overcurrent)? 2. Isn’t the circuit of the contactor the same as the circuit of the electrical equipment? The circuit voltages for contactors are 24V, 220V, and 380V, right? 3. Under what circumstances should the backfire contactor be used? 4. Is an overload protector a device for protecting against overload (excessive current)? Does it cut off the main circuit or the control circuit of the contactor? 5. What is the function of a thermal relay? What is the difference between it and an overload protector? Does it cut off the main circuit or the control circuit of the contactor?
1. Circuit breakers used in general industrial applications are primarily for short-circuit protection; although some of them also provide leakage protection as well. However, due to their high current rating, for example, a 6A circuit breaker may require a current 7–10 times higher in order to be triggered to shut off immediately. Think about it – which electrical device can tolerate such a large excess current? 2. The circuit of the contactor can be on the same circuit as the electrical equipment, or it can be on a different circuit. The common voltage choices for contactor coils are 24, 220, and 380; there may be special options as well, but I haven’t used them ； 3. Every contactor has a maximum current capacity; if no protection is in place and the current exceeds the allowable level for that contactor, its coil can be damaged as a result ； 4. An overload protector is essentially a type of overcurrent protector; it actually cuts off the power supply to the coil of the AC contactor. Once the AC contactor loses its coil power, it immediately disconnects the main circuit, thereby breaking the connection to the electrical equipment in that circuit. 5. A thermal relay is also a type of overload protector. Its function is to cut off the power supply to the coil of the AC contactor, causing the contactor to lose power and thus disconnecting the main circuit