Every time I buy a Bell electric car, it is fully charged. When it is unplugged, the voice prompts that there is undervoltage protection. Please charge in time. What do you mean,

Undervoltage protection is the action of protecting electrical appliances when the line voltage drops to the critical voltage, which is called undervoltage protection. Its main task is to prevent equipment from burning due to overload. This is to remind users that they need to charge in time, otherwise the battery will be damaged.

Due to short circuit fault and other reasons, the line voltage will be greatly reduced or even disappeared in a short time. It will bring damage to lines and electrical equipment. For example, the motor is exhausted and blocked, resulting in overcurrent several times the rated current and burning out the motor; When the voltage is restored, the self-starting of a large number of motors will greatly reduce the voltage of motors, causing harm.

Extended data:

Undervoltage protection of motor?

This kind of protection is mostly used in the motor control circuit of dragging important equipment, and the power of this kind of motor is generally higher than that of other motors on the bus. Its principle is that the normally closed contacts of the low-voltage relay are connected in parallel in the motor trip circuit, and the coil of the low-voltage relay is connected in parallel between the two phases of the bus providing three-phase power for the motor.

During normal operation, the power bus voltage is normal, the low-voltage relay coil is in the return state, its normally closed contact is disconnected, and the trip circuit is not connected. When the bus loses power supply due to some fault such as grounding or the bus voltage drops to the action value of the low-voltage relay, the relay acts, the normally closed contact is closed, the trip circuit is connected, and the motor and the bus are cut off.

When the bus voltage is restored, the low-voltage relay returns and the normally closed contact is disconnected to disconnect the trip circuit, so that the motor can be restarted.

Baidu Encyclopedia-Undervoltage Protection