Difference between expensive and cheap robot vacuums(1) – Brushed DC and Brushless DC motor

There\’re many models of vacuum cleaners and robot vacuums in the market. And the prices vary from dozens to thousands of dollars. You must be wondering the difference between them when they all looked pretty much the same. Come find out with me then!

(1) Brushed DC motor and Brushless DC motor(BLDC)

One of the most important parts of a vacuum cleaner or robot vacuum is the motor. And there\’re brushed DC (BDC) and brushless DC (BLDC) motors. Generally speaking, BLDC motors are better than BDC motors.

The brushless motor has a strong anti-interference ability, low running noise, and high efficiency. In addition, the brushless motor has a longer service life and requires little maintenance. The brushed motor has a simple structure, low production cost, and relatively mature technology. However, the carbon brush inside will wear out. When the wear reaches a certain level, the carbon brush needs to be replaced. Although the cost is not high, it is quite troublesome for ordinary people. Therefore, most high-end vacuum cleaners and robot vacuums use brushless motors to achieve a long life span and less trouble.

But what exactly is the difference between a BDC motor and a BLDC motor?

A BDC motor means it has a brush inside. And this brush is made of carbon, used for connecting with the commutator and making the rotor an electromagnet to spin. See the picture below for reference.

The BDC motor has a fast-starting response speed, large starting torque, stable speed change, almost no vibration from zero to maximum speed, and can drive a larger load when starting. Therefore, BDC motors are also commonly used in equipment with heavy loads.

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The BLDC motor doesn\’t have a carbon brush inside. Although the BLDC motor, like the brushed DC motor, still rotates the rotor by changing the direction of the magnetic field, in this case, the rotor is the magnet while the stator is the coil. See the picture below for reference.

The brushless motor has no brushes, the friction force is greatly reduced during operation, the operation is smooth, and the noise will be much lower. This advantage is a huge support for the stability of the product. Without the brush, the wear of the brushless motor is mainly on the bearing. From a mechanical point of view, the brushless motor is almost a maintenance-free motor. Therefore, the BLDC motor has considerable advantages in the parts that need to provide high speed for a long time.

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For the fan motor, which creates a vacuum and provides suction, the major requirement for the motor is to provide high spinning speed. So the brushless motor will be a perfect choice. But for the relatively high price, it\’s mostly used on high-end vacuum cleaners.

At present, except for Dyson, NIDEC\’s brushless motor technology is the best in the vacuum cleaner industry, and there is no patent problem. So most companies use NIDEC\’s BLDC motor in their high-end cordless vacuums cleaners.

In conclusion, those cheap vacuum cleaners are very likely to use brushed DC motors while expensive vacuum cleaners must be using brushless DC motors, otherwise it\’s fooling you.

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