Characteristics of series motor

There are many types of motors, but according to the power supply, they are nothing more than AC motors and DC motors. So is there a motor that can use both AC and DC power?

A single-phase series-excited (series-excited) motor is one such motor.

The series motor is powered by an AC power supply, and the series motor itself is a classic DC motor. The excitation winding and the armature winding of this type of motor form a series circuit through brushes and commutators, which has extremely unique advantages: it can work with both AC and DC power supplies; it has a high operating speed, small size, and light weight; it has smooth speed regulation, a wide range, and simple and reliable control; the speed is basically constant when it is less than the rated load, and it drops rapidly when it exceeds a certain load value. Therefore, most power tools use series motors, and the excellent characteristics of simple operation, high cost performance, safety and reliability have established the solid position of series motors in the field of power tools.

As a motor working on the principle of electromagnetic induction, the series motor has the following characteristics:

Large torque: The excitation current of the series-excited motor passes through the armature winding and interacts with the armature to produce a magnetic field. Therefore, the torque is relatively large and is suitable for occasions with large load changes.

Wide speed range: The speed range of the series-excited motor is wide and the speed can be adjusted according to different working conditions and requirements.

High reliability: The series-excited motor has a simple structure and no sliding contact parts, so it has a long life and high reliability.

But the power factor is low: the excitation current of the series-excited motor is in phase with the armature current, so the power factor is low and it is easy to generate large reactive power.

Poor stability: Due to the influence of back electromotive force, series-excited motors are prone to oscillation and unstable operation.

Narrow scope of application: Series-excited motors are suitable for situations where load changes are large within the small and medium power range, but are not suitable for high-power situations.

In short, the series motor has certain advantages and limitations, and needs to be selected and applied according to specific working conditions and requirements. During the application process, its characteristics and performance need to be evaluated and adjusted to improve its efficiency and reliability.

The rotor part of the series-excited motor is an armature composed of "coil + commutator", which is directly connected to the excitation winding of the stator part through carbon brushes. Therefore, the armature current and the excitation current are exactly the same. Although it is essentially a typical DC motor, it is different from ordinary DC motors, that is, the starting torque is larger and the characteristics are softer. Therefore, series-excited motors are widely used in power tools instead of ordinary DC motors.