Why can a hollow-cup drone's motor not turn but it can still transmit images normally?

If a hollow-cup drone can transmit images normally but the motor doesn't turn, it means the image transmission system itself is not faulty. The problem is likely in the motor, ESC, propellers, or power supply-components related to power output. Here are the specific causes and troubleshooting directions:

1. Motor Fault

• Motor Stall: If sand, water, or foreign objects get into the motor, the rotational resistance will increase, potentially causing it to seize up. Manually turn the motor after powering off. If you feel a noticeable jamming, this is likely the problem. Removing the foreign objects should solve it.

• Winding Fault: After prolonged high-load, high-temperature operation, the insulation layer of the motor windings may age and break, leading to short circuits or open circuits. You can use a multimeter to measure the three-phase winding resistance. The normal range is generally 0.1-0.3Ω (varies depending on the model). If the three-phase resistance difference exceeds 10%, it indicates a winding problem.

• Permanent Magnet Demagnetization: Neodymium iron boron (NdFeB) magnets have a Curie temperature of 310-400℃. If the motor overheats or experiences severe vibration, the permanent magnets will irreversibly demagnetize, resulting in insufficient motor torque and inability to start.

• Hall Sensor Failure: Sensing brushless motors rely on Hall sensors to detect rotor commutation. If the sensor is faulty, the wiring is loose, or there is signal interference, commutation will be disordered, preventing the motor from starting.

2. ESC-Related Issues

• ESC Mismatch or Incorrect Parameters: Incompatibility between the ESC's current and voltage specifications and the motor, or incorrect starting voltage and acceleration parameters in the firmware, will prevent the motor from starting. Swapping the ESC of the faulty motor with that of a normal motor can quickly pinpoint the problem.

• Abnormal ESC Signal: If the flight controller emits an unlock tone but the ESC does not respond, the signal cable between the flight controller and the ESC may be loose, or the flight controller firmware may have configured the motor pins as servo mode. Check the wiring and firmware configuration.

3. Propeller Malfunction: Mixing propellers (either positive or negative), incorrect installation direction, or cracks or deformation of the propeller can cause abnormal motor load and prevent normal rotation. Check the propeller's installation direction and appearance.

4. Power Supply Issues:

• Insufficient Battery Voltage: When the voltage of a single lithium polymer battery cell is below 3.5V, or the total voltage of a 4S battery is below 15.2V, low-voltage protection will be triggered, directly disabling the motor. Use a multimeter to measure the battery voltage. Also check for bulging batteries and oxidation/blackening of the connectors. Oxidation increases contact resistance, leading to insufficient power supply.

• ESC Power Supply Malfunction: If the ESC's LEDs are not lit, or the flight controller is working normally but the ESC is unresponsive, measure the ESC's BEC output voltage (normally 5V) and the main power input voltage to troubleshoot the power supply circuit.