Drawings

Single-phase universal motor, commonly known as series excited motor or general motor, is named after the excitation winding and excitation winding working in series. Single-phase series excited motors belong to the category of AC and DC dual purpose motors, which can work with both AC and DC power sources.

Single-phase series excited motors have high speed, small size, light weight, and convenient speed regulation, so they are used as power sources in the vast majority of electric tools. However, the single-phase series excited motor used in electric tools frequently starts, with high speed, high vibration, uneven load, and easy blockage, resulting in a sharp increase in armature temperature rise. It is precisely because of these characteristics that high requirements are placed on the manufacturing quality of single-phase series excited motors. Single phase series motor is mainly composed of three parts: stator, armature, and casing, with the highest requirement for armature.

The motor is mainly composed of three parts: stator rotor and bracket. The stator is composed of a salient pole iron core and excitation winding, while the rotor is composed of a hidden pole iron core, armature winding, commutator, and shaft. A series circuit is formed between the excitation winding and the armature winding through brushes and commutators.

Single-phase universal motors are widely used in the fields of electric tools, kitchen supplies, and floor care products due to their wide adjustable speed range and high starting torque.

Differences from induction motors

1. There are carbon brushes inside the universal motor, which will gradually wear out. Sparks during operation, strong electromagnetic interference, high speed, and coils on both stator and rotor. Induction motors, without carbon brushes (commutators), are usually started by capacitors and are usually squirrel cage type. The stator is a coil, the rotor is made of cast aluminum, and single-phase motors are generally below 3000 rpm (the speed is inversely proportional to the number of poles).

2. The universal motor has high noise and starting torque, making it suitable for both AC and DC applications. The noise of induction motors is relatively low.

3. The later maintenance costs are different. Brushed motors need to be replaced from 200h to 1000h according to different usage environment conditions. Long term operation of brush motors can easily cause carbon powder accumulation, leading to a decrease in motor insulation. In addition, there may be commutation sparks generated, and safety protection or explosion-proof motors must be used in fire-resistant and explosion-proof areas. Induction motors, on the other hand, completely avoid these weaknesses. As long as the bearings are not damaged, the motor generally does not fail and has a longer lifespan.