Choosing the right circuit breaker, contactor, and thermal relay is an important step to ensure the safety of the circuit, and it needs to be selected according to the amount of current in the circuit. Here are the basic steps and considerations for choosing these devices:
Circuit breaker:
The rated current of the circuit breaker should be greater than the maximum expected current in the circuit. Normally, the rated current of the circuit breaker is selected as 125 times. If the device is at a light load, consider choosing a circuit breaker that is slightly smaller than the calculated current.
Circuit breakers are divided into two categories: molded case circuit breakers and miniature circuit breakers, which are generally selected according to the load. In the power circuit, molded case circuit breakers are commonly used for high-power electrical appliances;In lighting circuits, miniature circuit breakers are commonly used for low-power electrical appliances.
Contactor:
The rated current of the contactor should be greater than the rated current of the motor, and the starting current of the motor should also be considered. For frequently started motors, a contactor with a higher rated current should be selected.
There are two types of contactors, AC and DC, which are used for AC circuits and DC circuits, respectively. When selecting, it is necessary to select according to the power supply type of the actual circuit.
Thermal Relay:
The rated current of the thermal relay should match the rated current of the motor. When using a thermal relay, it should be set at 1 of the normal operating current of the motorAbout 25 times. In this way, when the current is too high, the thermal relay will disconnect the circuit and protect the motor from burning out.
In addition to the current size, other factors need to be considered, such as the breaking capacity of the equipment, the working environment, the installation method, etc. Different types of devices and different brands may also have their own usage specifications and considerations.