Summary
Describes the working principle, design and manufacture, advantages and disadvantages of brushed DC motors (PMDC) and brushless DC motors (BLDC) used in portable power tools, as well as the current situation and prospects of market applications.
Keywords
Power tools, brushless DC motors
Guideline
IEC60841 / EN60745
1.Introduction
With the improvement of new batteries and electronic control technology, the design and manufacturing cost of brushless DC motors have been greatly reduced. Convenient rechargeable tools that require brushless DC motors have become popular and more widely used. It is widely used in industrial manufacturing, assembly, and maintenance industries. Especially with economic development, the demand for households is also getting higher and higher, the annual growth rate is significantly higher than in other industries.
2.Convenient rechargeable electric tool motor application type
2.1 Brushed DC motor
The structure of a conventional brushed DC motor includes a rotor (shaft, iron core, winding, commutator, bearing), stator (chassis, magnet, end cover, etc.), carbon brush assembly, carbon brush arm, and other parts.
Working principle: The stator of the brushed DC motor is equipped with fixed main poles (magnets) and brushes, the armature windings and commutators are installed on the rotor. The electrical energy of the DC power supply enters the armature winding through the carbon brushes and the commutator to generate an armature current. The magnetic field generated by the armature current interacts with the main magnetic field to generate electromagnetic torque, which makes the motor rotate to drive the load.
Disadvantage: Due to the existence of carbon brushes and commutators, brushed motors have poor reliability, many failures, unstable current, short life, and commutation sparks will produce electromagnetic interference.
2.2 Brushless DC motor
The conventional brushless DC motor structure includes the motor rotor (shaft, iron core, magnet, bearing), stator (chassis, iron core, winding, sensor, end cover, etc.), and the controller and other parts.
Working principle: The brushless DC motor is composed of the motor body and the driver and is a typical mechatronic product. The working principle is the same as the brushed motor, except that the position sensor and control circuit replace the traditional commutator and carbon brush. sending control commands through sensing signals to complete the current direction conversion to achieve commutation work, ensure that the motor produces constant electromagnetic torque and steering to make the motor rotate.
3. Disadvantages of BLDC motor:
3.1 High cost:
Most of them use neodymium iron boron (Nd-Fe-B) strong magnets as rotor poles, which are rare earth raw materials, are expensive, and are strategic materials. Controller design and manufacturing costs are high.
3.2 High requirements:
The structure and control system design is complex, and more professional mechanical and electronic control technicians are required.
4 summary
As major international economies promote modern industrial manufacturing upgrades and fully develop toward advanced intelligence; the quality of life of global families has improved, and power tools are gradually requiring smarter, long-life, safe, and vibration-proof high-end experiences.
High-end rechargeable types such as electric wrenches, electric screwdrivers, electric hammer drills, etc., and other convenient electric tools such as electric saws used in brushless DC motors will become more and more widespread in industrial applications and household markets.
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