Excessive starting current is a common problem with micro DC motors and can lead to a variety of problems, such as overheating of the motor, excessive wear of the brushes, and even burnout. Starting currents are usually several times greater than normal operating currents and can cause serious damage to the motor if not handled properly.

The first major cause is the magnetic properties of the stator and rotor, which determine the starting torque of the motor. The starting torque is proportional to the product of the stator and rotor magnetic fields. If the magnetic fields are too strong, the motor will require more current to overcome the initial inertia and start spinning.

Another factor that may contribute to excessive starting current is friction between the brushes and the commutator. During startup, the brushes may experience a lot of friction due to the high current. This can lead to excessive wear of the brushes, which in turn leads to poor contact with the commutator, further increasing the starting current.

Poor electrical connections can also lead to excessive starting currents in micro DC motors. If the electrical connection between the motor and the power supply is poor, the motor may not receive the full current needed to start. This can cause the motor to draw more current than required, resulting in excessive starting current.

Motor loading can also cause excessive starting current. If the motor needs to start under a heavy load, more current is required to overcome the initial inertia and start spinning. This causes the motor to draw more current than it would under light load, resulting in excessive starting current.

In order to reduce the excessive starting current of micro DC motors, several steps can be taken.
First, the magnetic characteristics of the stator and rotor should be carefully designed to provide the necessary starting torque without generating excessive current. Second, brushes should be carefully selected and properly lubricated to minimize friction and wear. Third, the electrical connections between the motor and the power supply should be checked for good contact and proper resistance. Fourth, the motor load should be carefully controlled to minimize the required starting current.

In summary, excessive starting currents in micro DC motors can be caused by a number of factors, including magnetic characteristics, friction between brushes and commutator, poor electrical connections, and heavy loads. To reduce excessive starting currents, the motor’s magnetic characteristics must be carefully designed, brushes must be selected and properly lubricated, electrical connections must be checked, and motor loads must be controlled. By addressing these issues, starting currents can be reduced and the life of the micro DC motor extended.