1、 Basic classification and working principle of household motors
Household motors can be divided into two categories based on their power supply: AC motors and DC motors.
AC motor: driven directly by mains power (such as 220V/50Hz AC power in China).
The most common type is single-phase asynchronous motor (also known as induction motor).
Its stator is fed with alternating current to generate a rotating magnetic field, and current is induced in the rotor winding to drive the rotor to rotate.
The structure is simple, sturdy and durable, with low cost, but the starting torque is small and the speed regulation is difficult (usually requiring changes in power frequency or pole pairs, resulting in high cost).
DC motor: requires direct current drive.
Traditional DC motors have commutators and brushes, which continuously rotate the rotor by changing the direction of current. The advantage is that speed regulation is convenient (voltage adjustment is sufficient), but the brushes are prone to wear, sparks, and noise.
With the development of electronic technology, modern household appliances have adopted a large number of brushless DC motors. They place permanent magnets on the rotor, and the stator winding is sequentially energized by an electronic controller, removing the electric brushes. This not only retains the advantages of smooth speed regulation of DC motors, but also achieves high efficiency, long life, and low noise.

2、 Why have traditional household appliances been dominated by AC motors for a long time?
Looking back at household appliances in the 20th century, the vast majority used AC motors.
The reason is very practical:
Power matching: The household socket directly provides AC power, and using an AC motor does not require any conversion circuit, just plug it in and use it.
DC motors require rectifiers or transformers to convert AC to DC, and early electronic components were bulky, expensive, and inefficient.
Cost advantage: The structure of AC asynchronous motors is extremely simple – stator core+coil, rotor is made of cast aluminum or copper rod squirrel cage, without commutator, brushes, or permanent magnets.
Under large-scale production, the cost is extremely low and the reliability is high.
Sufficient to meet the demand: Traditional household appliances have a single function, such as electric fans, washing machines, refrigerator compressors, etc., which only require constant speed or simple gear switching, without the need for fine stepless speed regulation.
The methods of using AC motors in conjunction with capacitor starting and tap speed regulation are basically sufficient.
Therefore, old-fashioned electric fans, exhaust fans, range hoods, fixed frequency washing machines, fixed frequency refrigerators, fixed frequency air conditioners, etc., all have AC asynchronous motors inside without exception.
Until today, many cheap or basic household appliances still heavily use AC motors.

3、 Why have DC motors (especially brushless DC) rapidly emerged in recent years?
Since the 1990s, especially after entering the 21st century, the proportion of DC motors in household appliances has been increasing, and even become a standard configuration for mid to high end products.
There are three core factors driving this transformation: energy conservation, speed regulation performance, and reduced electronic costs.
Significant energy-saving advantages: AC asynchronous motors have low efficiency at light loads or low speeds, while variable frequency air conditioners, variable frequency refrigerators, etc. require long-term operation at different speeds.
The efficiency of brushless DC motors can reach over 85% to 90%, while small AC motors typically only have 50% to 70%.
For devices that operate continuously (refrigerators, air conditioners, fans), switching to a DC motor can save up to 30% to 50% of electricity.
Against the backdrop of increasingly strict national energy efficiency standards, DC motors have become a key technology for achieving standards.
Perfect stepless speed regulation and silence: The DC motor can easily achieve smooth adjustment from zero to maximum speed by changing the duty cycle of the PWM (pulse width modulation) signal, and it is very quiet when running at low speeds.
This allows the DC variable frequency fan to blow out a soft ‘sleep breeze’;
DC vacuum cleaner can automatically adjust suction according to the type of floor;
The robotic vacuum cleaner can accurately control the wheel speed.
To achieve the same performance, AC motors require complex variable frequency drive circuits, which actually result in higher costs.
The development of power electronics and magnetic materials: The popularity of high-performance permanent magnet materials (such as neodymium iron boron) and the emergence of low-cost and high reliability MOSFET/IGBT control chips have brought the price of the entire solution for brushless DC motors to an acceptable range.
Nowadays, you can buy a brushless DC motor with a controller for just a few tens of yuan.