Motor forward rotation control issue

When a motor stops suddenly, it is usually related to the circuit protection or control devices. Since you mentioned an automatically resetting thermal relay, we can consider the following possible scenarios: 1. Overload protection activation: The motor may experience overload during operation, which causes the thermal element of the thermal relay to heat up and activate, thereby cutting off power to the motor to protect it. The thermal relay is equipped with an automatic reset function; once the overload condition is resolved and the thermal element cools down, the thermal relay resets automatically, allowing the circuit to be reconnected and the motor to restart. 2. Power supply fluctuations or brief interruptions: The power supply system may have instability issues, such as voltage fluctuations or brief interruptions. If the power supply to the motor is unstable, it may result in a current level that is not sufficient to maintain the engagement of the contactor; as a consequence, the contactor disconnects and the motor stops running. Subsequently, the power supply stabilized again, allowing the contactor to close once more, and the motor could start up again. 3. Thermal relay failure or malfunction: The thermal relay itself may be faulty, or it may malfunction without any overload, causing the motor to stop. Once the thermal relay is reset, the motor can start again normally. 4. Control circuit failure: Intermittent faults may exist in the control circuit, such as poor contacts or problems with the coils of relays or contactors, which prevent the motor from running continuously. The fault is repaired, or due to changes in certain external conditions such as temperature or vibration, the fault may temporarily disappear and the motor can restart. After each restart of the motor, it is necessary to check whether it is operating properly; if such situations occur frequently, more thorough inspection and maintenance should be carried out. The staff can check whether the thermal relay is damaged or misconfigured, verify the stability of the power supply, and inspect whether the connections in the control circuit are proper. If the problem still cannot be resolved, it is recommended to contact a professional technician for inspection and repair. .

During operation, sudden stopping occurs because the load increases to an excessive level for some reason, causing the thermal element of the thermal relay to activate; this leads to the opening of its normally closed contacts, resulting in a loss of power to the control circuit and thus the motor stops. After some time, the heating element of the thermal relay cools down, and its normally closed contacts close again, allowing the circuit to be restarted and operate normally.