Principle of series motor

The working principle of the series motor is the same as that of the DC motor, and the left-hand rule and the right-hand rule can fully explain its principle.

The principle of the series motor is based on the interaction between the magnetic field and the magnetic field generated when the current passes through the winding. The current flow path in the motor is: external power supply → brush → rotor winding → stator winding → brush → external power supply.

When current flows through the rotor windings, a magnetic field is generated within the windings. Due to the arrangement of the windings and the direction of the current, the generated magnetic field interacts with the stator poles to create a torque that causes the rotor to start rotating. As the rotor rotates, the brushes continually contact different parts of the rotor windings, changing the direction of the current in the windings and causing the rotor to continue rotating. Thus, a series-excited motor can convert electrical energy into mechanical energy.

In a series-excited motor, the interaction between the rotor winding and the stator poles is in series, that is, each pole on the stator only affects a section of the rotor winding adjacent to it. This structure makes the output torque of the series-excited motor proportional to the current, so when the load is large, the output torque and current will increase, but the efficiency of the motor will decrease.

It should be noted that the series-excited motor requires an external power supply to provide current, so a DC power supply is required. In practical applications, the DC power supply can be obtained from the AC power supply through power electronic devices (such as rectifiers). At the same time, in order to control the speed and output torque of the motor, different control methods (such as speed regulators and current controllers) can be used to adjust the current size and direction.

In a series-excited motor, the relationship between output torque and current can be expressed as:

T = k * I

Where T is the output torque, I is the current, and k is the proportional constant. Since the output torque of a series motor is proportional to the current, when the current increases, the output torque will also increase accordingly.

However, as the load increases, the efficiency of the motor decreases. This is because as the load increases, the motor needs to output more torque to overcome the load, which causes the motor current to increase. However, due to factors such as the motor's winding resistance and mechanical friction, some of the electrical energy is converted into heat energy, so the efficiency of the motor decreases.

In order to improve the efficiency of the motor, some measures can be taken, such as using efficient insulation materials, optimizing the design and manufacturing process of the motor, and reducing the load on the motor.

In short, the principle of the series motor is based on the interaction between the magnetic field and the magnetic field generated when the current passes through the winding. The series motor has the characteristics that the output torque is proportional to the current. In practical applications, the efficiency and control method of the motor need to be considered to meet different application requirements.