When starting the motor, it needs a lot of current. This key is used to control the starting motor. When the key is turned on, if a large current flows from the key to the starter. Then the key must be big and heavy, able to withstand the frequent passage of large current without being burned out, and it is also necessary to connect the battery, the key and the starting motor with thick wires.
This is uneconomical, unreliable and inconvenient to maintain. People invented the starting relay, so that the starting current can reach the starting motor directly from the battery through the relay, and it must be controlled by the key at the same time. The control current through the key is very small, and the wire is very thin, which increases the life of the key.
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Matters needing attention in the use of automobile main relay:
1, rated voltage is the guarantee of relay working reliability. Although the relay can work when the coil voltage exceeds the working voltage, it will fail under strong impact; If the voltage of the coil exceeds maximum working voltage, the insulation of the coil will be reduced, and the turn-to-turn short circuit will burn out.
2. Due to the change of ambient temperature and the heating of relay itself, the coil resistance of relay will change by 0.4[%] per℃. Therefore, if the coil temperature increases, the operating voltage and the disconnection voltage will also increase. Automobile relay is driven by battery, which will reduce the power supply voltage when connected with a large load and affect the relay life.
3. Maximum continuous applied voltage of the coil: The maximum continuous applied voltage of the coil not only affects the stability of the relay, but also is mainly limited by the insulation performance of the enameled wire, so it is necessary to know the insulation grade of the enameled wire of the product. When the ambient temperature of class F insulation is 40℃, the maximum temperature rise can be limited to 1 15℃.
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