Is the car relay hot is normal

Update:27-07-2019
Summary:

The car relay is hot. From the perspective of physics, […]

The car relay is hot. From the perspective of physics, it is a process in which mechanical motion generates heat and mechanical energy is converted into heat. This is a normal phenomenon. This is also the reason why radiators are installed in many machines. When a large amount of heat is generated during the movement of the machine, we will install a heat sink to lower the temperature. If the temperature is too high, this is an abnormal phenomenon.
It is normal for the relay coil to be slightly hot during normal operation, but if the contact is hot, the service life of the relay has expired and should be replaced. Otherwise, the line fault will be caused by the contact contact resistance being too large (the voltage drop is too large). If the contact is not replaced, the contact resistance will cause further oxidation, and the hot phenomenon will be more serious, which may cause a fire in extreme cases.
The phenomenon of hot relay and its causes are as follows:
1. Abnormal heat occurs in the center of the contact part, and the joint has melting, melting, dissolution and solidification, and the operation is poor. That is because the repeated switching of the contacts causes the continuous opening and closing of the arc.
2. The circuit inside the relay is blown and the contact dissolves and solidifies, and the operation is poor. This is most likely due to an abnormal overcurrent that exceeds the rated current of the contact.
3. The coil is partially short-circuited, the coil is broken, and the coil remains abnormally hot. It may be that an overvoltage is applied to the coil.
The solutions to the above phenomena are:
1. The voltage of the relay of AC specification should not be lower than 90% of the rated voltage; the voltage of the relay of DC specification should not be lower than 79% of the rated voltage; avoid the high frequency switch.
2. Safety design of the circuit to prevent the rated current exceeding the contact from flowing through the contact circuit.
3. Do not apply a voltage above the rated voltage on the coil.
The car relay is not normal. We first judge the temperature. If the temperature is too high, it is an abnormal phenomenon. If there is an abnormality, we have to eliminate it. Don't drag it, drag it to the back and the problem is more serious. If we can't solve it ourselves, then we should seek help from professionals and try to reduce the loss to a smaller extent.