Brushed v brushless motor

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When designing compact motor drive programme , the first choice user makes is between brushed and brushless dc motors.

Undoubtedly, both types of motors have advantages and disadvantages, but which type is more suitable for specific applications? It requires analysis of characteristics of both type.

First, service life

The mechanical reversing system of the brushed motor directly affects its service life. The reversing system is directly affected by the load condition. The large current, high speed, reverse motion and high strength vibration generated during operation will reduce its service life.

Brushed motor

The brushless motor used an electronic reversing design instead of a mechanical reversing design, which greatly prolongs motor life and reduces maintenance. Moreover, the life of the motor can be predicted relatively accurately. For example, ball bearing will limit the service life of the motor, and the service life of the motor can be accurately inferred through the design life of the bearing.

Brushless motor

Secondly, motor speed

Because of reversing system, the speed of brushed motor is generally less than 10,000 rpm. In over speed operation, the service life of the motor will be greatly shortened due to the increase of electrical and mechanical wear.

Brushless motors of the same size and magnetic structure can operate at higher speeds, even more than 100,000 rpm.

Thirdly, use environmental conditions

Brush reversing systems may generate sparks that can cause electromagnetic interference. Graphite dust from brushes can contaminate clean rooms, vacuum or optical applications.

At last,Motor control and operation

Brush motor is easy to operate, as long as the voltage is enough, the motor can start to work.

While BLDC motor requires additional electronic reversing control equipment and more complex wiring. But in applications which precise control is needed, the cost and wiring is the same for both types. With BGM’s brushless motor kits, the wiring can be done in 1 second, and speed can be adjusted by the knob easily. What’s more, the price of this bldc motor kits is low, as we cut down reductant function to save cost.

To sum up,

BLDC motor is more adaptable to different environmental conditions. It has longer service life , and has advantages on high speed applications.

 In simple drive applications, the wiring and cost of brushed motors are more dominant, and the two are similar in precise control situations.

Of course, the final choice also needs to be considered in all aspects according to the specific application scenario.

Types of brushless dc motor

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There are kinds of brushless motors on the market. Types of brushless DC motors vary in their power, voltage, control technology, and installation mode, providing a wide range of options for various applications.

1. The power of the BLDC motor ranges from tens of watts to several kilowatts. P(W)*10= rated speed * torque. For example, a 70W bldc motor is often used for house cleaner, while 200-400w bldc motors are usually used in conveyors, packing machines and so on. Large stepper motor such as 750-1500w are usually found in industrial automation production line.

Bldc motor in conveyor

2. Rated voltage. According to voltage, BLDC motor can be classified as 12V BLDC motor, 24V BLDC motor, 48V BLDC motor,  110VAC and 220VAC BLDC motor and so on. Dc power supply is suitable for mobile devices and devices with high-security requirements, such as entertainment facilities. While AC power supply is easier to obtain.

3. Brushless motor flange sizes. The brushless motor has flange size of 42*42mm, 60*60mm, 90*90mm,110*110mm and so on. It can also be customized according to customer requirements.

4. Control technology. There are square wave control, sine wave control,  FOC, and encoder control.

5. Product structure. BLDC motor can be divided to with hall, without hall, and linear hall. At present, the most common product in the market is the brushless motor with hall sensor, which is also main product of ICAN. After adding a hall senor, the speed and torque of BLDC motor is increased.

6. Installation mode: panel, case and embedded. If BLDC motor driver is with panel, It’s easier to for the user to control. For example, Ican’s BGM series bldc motor kits, the speed can be adjusted by the knob. On the panel with display, users can get speed, current information and so on.When the driver is placed in case, user should open the case to adjust the driver, such as ICAN BLDC-750,BLDC-300. Sometimes, the BLDC driver is without shell, and embed to user’s system.

BGM series BLDC motor kits

7. The combination of motors and other components. Brushless motors are often combined with reducer, brake or other components. Brushless motor with reducer is called gear motor. The most common gear motors are with gearbox, planetary gearbox , L type reducer, right-angle reducer and turbine reducer.

BLDC motor with planetary gearbox

8. Rated speed. There are many kinds of motors with different speeds on the market, such as 1500rpm, 3000rpm, 4000rpm and 6000rpm. Most of ICAN’s products are 1500, 3000 rpm motors.

9. The number of poles. According to the number of poles, BLDC motor can be divided into 2 pairs , 4 pairs , 5 pairs of poles. The driver pole log setting should be consistent with the motor pole log, otherwise the motor cannot operate normally.

10. Type of input signal source. There are four types of brushless motor signals:

  • Analog signal.  Analog signals can be build-in or external input. If it is external, it requires PLC to output analog signal. Or an extra module is necessary to output analog signal to the controller.
  • Pulse frequency. Similar to stepper motor speed control, the speed of the BLDC motor is controlled by the pulse frequency.
  • The motor speed is controlled by adjusting duty ratio. Duty ratio is the proportion of time of high level in a pulse cycle.The motor rotates at high level and stops at low level.
  • Communication method.  Communication signals are often used in multi-point control situations. RS485 and CANopen are commonly used recently. ICAN also has many controllers with RS485 70W-1500W for customers to choose.

In conclusion, the diverse array of brushless DC motor types available in the market today enables industries to find tailored solutions that meet their specific requirements. As technology continues to advance, these motors will undoubtedly play an important role in motion control .

57mm bldc motor

What are differences between BLDC motor and AC motor

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The brushless motor system consists of a motor and a brushless motor controller.  Since the BLDC motor runs in a self-controlled manner, it has no additional starting winding to the rotor as the asynchronous motor. Even if the load changes suddenly, there will be no oscillation or out-of-step.

sh kitsAC motor is a device that converts AC electric energy to mechanical energy. It mainly comprises electromagnet winding or distributed stator winding and a rotating armature or rotor.  There are synchronous AC motor and AC induction motor.

Compared with AC motors, the brushless motor has the following advantages:

  1. High torque at low speed. At low speeds, the torque of the AC motor is low, while the torque of the BLDC motor is much higher.
    bldc high torque at low speed
  2. Wide speed range. Generally, the speed range of the BLDC motor is 50-3000RPM, AC motor is 150-1350RPM. Moreover, the BLDC motor speed could be adjusted evenly and smoothly even under heavy load.
  3. High efficiency. The efficiency of the brushless motor is more than 75%, while the efficiency of the AC motor is only 30~40%. Therefore, brushless motor is more energy-saving, which is in line with the global trend of energy conservation and environmental protection
  4. Quick response. Similar to car starting, a car with superior performance accelerates quickly, and so does a brushless motor.
  5. Compact structure. At the same power, brushless motors are smaller than AC motors, so they require less raw materials and save more cost.
  6. DC or AC power input. If the BLDC motor driver is connected to AC, the driver converts AC to DC for the motor to work. If DC is input, the drive does not need to convert. Compared with AC, DC has the advantages of convenience and safety. For example, for AGV equipment, high torque brushless motor is widely used as it can be input DC. Because it’s safer, a brushless DC motor is often used for entertainment equipment.

Generally speaking, the selection of motors is based on all aspects of specific applications. Users are increasingly leaning towards DC motors, especially BLDC motors.

how to select a stepper motor

How to select a suitable stepper motor

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1. The choice of stepper motor torque

The holding torque of a stepper motor is similar to the “power” of a traditional motor. But the physical structure of stepping motors is completely different from AC and DC motors, and the output power of the motor is variable base on speed, current, and input voltage.

Generally speaking, if the needed torque is below 0.8N.m, choose nema8(20x20mm), nema11(28x28mm), nema14(35x35mm), nema16(39x39mm), nema17(42x42mm); if the torque is about 1N.m, choose the nema23 stepper motor. When the torque is several N.m or more, it is necessary to choose a stepper motor of nema34, nema42, and other specifications.

2. The choice of stepper motor speed

The output torque of the motor is inversely proportional to the speed.

That is to say, the torque of the stepping motor at low speed(a few hundred rpm) is high, but it is small when the stepper motor runs at high speed (1000 rpm-9000 rpm). For example:

torque 42H2P4812A4

Of course, some working conditions require high-speed motors, and the coil resistance and inductance of the stepping motor must be measured. Choose a motor with a smaller inductance, as a high-speed motor, can obtain a larger output torque. Conversely, when low speed and high torque are required, the inductance and the resistance should be larger.

3. Choose for the use environment of stepper motors

The special stepping motor is waterproof and oil-proof and is used on some special occasions. For special-purpose motors, it is necessary to select targeted ones. Customization is available for special usage.

4. Selection of the number of phases of the stepper motor

Generally, the stepper motor phase is not paid attention to customers. In fact, the more phases there are, the smaller the step angle can be made, and the smaller the vibration during work. In most cases, two-phase motors are chosen. In a high-speed and high-torque working environment, it is more practical to choose a three-phase stepper motor.

5. Special specifications selection according to the actual situation

Special specifications of stepper motors, for example, the diameter, length, lead screw, and direction of the output shaft can be customized.

 

 

 

 

6. Selection of no-load starting frequency of stepper motor

The no-load starting frequency of a stepper motor, usually called “idling frequency”. If it is required to start and stop frequently in an instant, and the speed is about 1000 rpm (or higher), it is usually necessary to “accelerate the start”. If you need to start directly to achieve high-speed operation, it is better to choose a reactive or permanent magnet motor, because the “idling frequency” of these motors is relatively high.

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