How to Choose a Auitable Motor, This Article Tells You

Posted by Jesse MayRC on

(2)The structure of the motor:

As the saying goes, a good understanding of a person must first understand its "inner core", then we have a complete understanding of the structure of the motor (for example, the outer rotating motor)

Let's take a look at its external structure:


Next is its internal structure:

2.The classification of the motor.

(1)Divided according to the type of power supply: can be divided into DC motors and AC motors.

(2)According to the structure, it is divided into internal rotation motor and external rotation motor.

The outer rotor, the rotor (magnet) rotates outside the stator (coil), and the inner rotor is the rotor (magnet) rotates inside the stator (coil); their different mechanical structures determine different performances.

*Generally, the rotation speed of the outer rotor is not higher than 2000KV, but the larger the diameter of the rotor, the larger the torque, which is equivalent to the inner rotor motor through a deceleration transmission

To obtain greater torque, in most cases, it is used in fixed-wing aircraft to directly drive large-diameter propellers. The outer rotor brushless motor has a large torque and a slow speed.

*There is a ventilation hood under the casing and end cover to prevent iron filings and other debris from falling in. The shell is also made into a baffle shape to prevent raindrops from splashing into it at a certain angle. The ventilation is very good. 


*The high speed of the inner rotor is generally higher than 2500KV, but due to the small diameter of the rotor, the torque is small. It is usually used in the occasions that require high speed and low torque. It can directly drive a small diameter propeller or obtain a larger propeller through a suitable reduction gear ratio. The torque of the brushless motor with the inner rotor is small and the speed is fast

* Its shell is hermetically sealed, cooled by its own fan or external fan, and has a heat sink on the shell. It can be used in places with a lot of dust, humidity or acid gas.



(3)DC motors can be divided according to structure and working principle: brushless DC motors and brushed DC motors.

*Brushless DC motors

As the name implies, the brushless motor has no brushes! His no-load resistance mainly comes from the rotating contact point between the rotor and the stator, so the general brushless motor uses ball bearings at both ends of the rotor to reduce friction! In this way, there will not be a lot of frictional resistance and heat (in fact, it will still generate heat, but the heat source comes from the resistance loss on the coil), and it has extremely high (over 80%-90%) efficiency and high speed! Generally used on models that require high-power output, providing excellent and strong power!

*Brushed DC motors.

The two brushes (copper brush or carbon brush) of the brushed motor are fixed on the back cover of the motor through an insulating seat and directly lead the positive and negative poles of the power supply to the inverter of the rotor, and the inverter connects the coil on the rotor , The alternating polarity of the 3 coils and the 2 magnets fixed on the housing form a force to rotate. Since the inverter is fixed with the rotor, and the brush is fixed with the housing (stator), the brush and the inverter are constantly rubbing when the motor rotates, generating a lot of resistance and heat. Therefore, the efficiency of the brushed motor is low and the loss is very large. However, it also has the advantages of simple manufacturing, low cost and low cost. It is widely used in Lama and Cupid, and it performs well!

  • Scope of application

    Brushless motor: usually used in equipment with relatively high control requirements and high speed, such as aircraft models, precision instruments, etc., which have strict control of motor speed and high speed.

    Brushed motors: usually brushed motors are used in power equipment, such as hair dryers, factory motors, household range hoods, self-balancing electric cars, and so on..

  •  Effect

    Brushless motor: usually digital frequency conversion control, strong controllability, from a few revolutions per minute to tens of thousands of revolutions per minute can be easily achieved. Brushed motors: The old carbon brush motors generally work at a constant speed after starting, and it is not easy to adjust the speed. The series motor can also reach 20,000 rpm, but the service life will be relatively short.

(4)DC motors can be divided according to the principle of induction: inductive brushless motors and non-inductive brushless motors.


The advantages of non-inductive motors: simple structure, low cost, convenient installation

Disadvantages of non-inductive motors: The rotor position detection accuracy is reduced, the running accuracy is reduced, and the start-up is not as stable as the inductive motor. It is not allowed to start with heavy load, and it is not allowed to start frequently and forward and reverse.

Disadvantages of induction motors: 

  • Under the conditions of high temperature and vibration, the reliability of the system is reduced due to the existence of the sensor.

2、Many sensor cables are inconvenient to install and easily cause electromagnetic interference.

3、The installation accuracy of the sensor directly affects the running performance of the motor, especially the installation accuracy of the multi-pole motor is difficult to guarantee.

4、Occupies space and limits the miniaturization of the motor.

Advantages of induction motors:

1.The advantage is that the sensor directly detects the position of the rotor, provides the starting current phase, has a large starting torque, and can be frequently started and reversed. It has high running precision and stable starting. It can be used in vehicles.

2.From the perspective of the governor, the price of an inductive motor with the same power is now more expensive than a non-inductive motor

3.In short, the main difference between these two types of motors is: There is an induction typebrushless motor, and a Hall sensor is installed inside to sense the position of the motor rotor and used to control the rotation of the motor. And the non-induction type brushless motor, then There is no Hall sensor inside, but another method is used to sense the rotor position to control the motor rotation.

3.the basic method of selection

1.Motor parameters: You must first understand the specifications and models of the motor, functional characteristics, protection type, rated voltage, rated current, rated power, power frequency, insulation class, etc. These contents can basically provide a reference basis for the user to correctly choose the protector.

2.Environmental conditions: Mainly refer to room temperature, high temperature, high cold, corrosion, vibration, wind and sand, altitude, electromagnetic pollution, etc.

3.Motor use: Mainly refers to the required characteristics of driving mechanical equipment, such as fans, water pumps, air compressors, lathes, oil field pumping units and other mechanical characteristics of different loads.

4.Control mode: The control modes include manual, automatic, local control, remote control, stand-alone independent operation, and centralized control of the production line. The starting methods include direct, step-down, star angle, frequency sensitive rheostat, frequency converter, soft start, etc.

5.Other aspects: the user's monitoring and management of on-site production, the severity of the impact of abnormal shutdowns on production, etc.

Will you choose when you see this
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