Due to the impact of the new crown epidemic, the global economy is generally depressed, and the home appliance industry has also been greatly affected. However, unexpectedly, the small home appliance market is extremely hot. Many small home appliance companies have full orders, and the performance of small home appliances and related companies has also risen sharply.

As a core component of electric small household appliances, the market for AC series motors has also developed rapidly. Compared with DC or induction motors, series-excited motors have the advantages of simple structure, mature technology, high power density, and high cost performance. They are widely used in small home appliances. However, series-excited motors have soft torque characteristics, and the motor speed changes greatly with load. , The shortcomings of poor speed regulation performance, etc., are subject to many restrictions in practical use. Especially in some multi-functional food processors, cook machines, multi-functional broken wall cooking machines and other products, simply relying on simple pressure reduction, tap speed adjustment and other control methods can not meet the requirements at all. For this reason, the above-mentioned series motor must be equipped with a powerful electronic speed control device to meet the performance requirements of the terminal product.

At present, the series motor speed control mainly has the following methods:

A multi-pole magnetic ring is installed on the motor rotor, and a Hall sensor is installed on the motor support. The Hall sensor converts the detected rotating magnetic field signal into a speed signal and sends it to the power controller.

A circular grating is installed on the motor rotor, and a grating sensor is installed on the corresponding motor support. The sensor converts the optical signal that changes with the high frequency of the rotation speed into a rotation speed signal and sends it to the power controller.

The power supply controller controls the output voltage according to the principle of negative feedback regulation according to the speed signal to stabilize the motor speed within a certain accuracy range. The power controller is divided into two types: SCR speed regulation mode and PWM inverter control.

After the series motor is equipped with the above negative feedback speed control device, the performance can be greatly improved, the speed range can be from tens to tens of thousands of revolutions, the speed changes smoothly, and the real stepless speed change is realized. At the same time, negative feedback control can limit the high speed at no-load, greatly reduce product noise, and reduce motor sparks. Moreover, the negative feedback function can make the motor automatically adjust the current according to the load at low speed, and the hardness of the motor torque characteristic is greatly improved, which solves the problem of The excitation motor speed fluctuates greatly, and the low gear torque is insufficient.

With the rapid development of today's power electronics technology, the development of various control semiconductor devices such as SCR, MOSFET, BJT, IGBT, GTO, etc. and the improvement of PWM control technology, negative feedback control power inverters have been widely used and the technology is mature. Compared with brushless DC motors, although negative feedback series motors have a certain gap in performance, they are low cost and cost-effective, so they have been widely used, such as drum washing machines, wall breakers, kitchen robots and other products. They are all series motors with negative feedback.