★Why do brushless DC motors have three Halls?
Answer: In short, in order to rotate the DC brushless motor, there must always be a certain angle between the magnetic field of the stator coil and the magnetic field of the rotor permanent magnet. The process of rotor rotation is also the process of changing the direction of the rotor magnetic field. In order to make the two magnetic fields have an angle, the direction of the magnetic field of the stator coil must be changed after a certain degree. So how do you know to change the direction of the stator magnetic field? Then it's up to those three Halls. Think of those three Halls as tasked with telling the controller when to change the direction of the current.
★What is the approximate range of power consumption of the brushless motor Hall?
A: The power consumption of the brushless motor Hall is roughly in the range of 6mA-20mA.
★How high temperature can the motor work normally? What is the maximum temperature the motor can withstand?
Answer: If the temperature of the measured motor cover exceeds the ambient temperature by more than 25 degrees, it indicates that the temperature rise of the motor has exceeded the normal range. Generally, the temperature rise of the motor should be below 20 degrees. Generally, the motor coil is made of enameled wire, and when the temperature of the enameled wire is higher than about 150 degrees, the paint film will fall off due to the high temperature, resulting in a short circuit of the coil. When the coil temperature is above 150 degrees, the temperature of the motor casing is about 100 degrees, so if it is based on its casing temperature, the maximum temperature the motor can withstand is 100 degrees.
★The temperature of the motor should be below 20 degrees Celsius, that is, the temperature of the motor end cover should be less than 20 degrees Celsius when it exceeds the ambient temperature, but what is the reason why the motor heats up more than 20 degrees Celsius?
Answer: The direct cause of motor heating is due to the large current. Generally, it may be caused by the short circuit or open circuit of the coil, the demagnetization of the magnetic steel or the low efficiency of the motor. The normal situation is that the motor runs with high current for a long time.
★What causes the motor to heat up? What kind of process is this?
Answer: When the motor is running under load, there is power loss in the motor, which will eventually become heat energy, which will increase the temperature of the motor and exceed the ambient temperature. The value by which the motor temperature is higher than the ambient temperature is called the ramp-up. Once the temperature rises, the motor will dissipate heat to the surroundings; the higher the temperature, the faster the heat dissipation. When the heat emitted by the motor per unit time is equal to the heat dissipated, the temperature of the motor will no longer increase, but maintain a stable and constant temperature, that is, in a state of balance between heat generation and heat dissipation.
★What is the allowable temperature rise in general click? Which part of the motor is most affected by the temperature rise of the motor? How is it defined?
Answer: When the motor is running under load, it is necessary to play its role as much as possible, that is, the larger the output power, the better the load (if the mechanical strength is not considered). But the greater the output power, the greater the loss of power, the higher the temperature. We know that the weakest thing in the motor is the insulating material, such as enameled wire. There is a limit to the temperature resistance of insulating materials. Within this limit, the physical, chemical, mechanical, electrical and other properties of insulating materials are very stable, and their working life is generally about 20 years. Exceeding this limit, the life of the insulating material is shortened sharply, and even burns out. This temperature limit is called the allowable temperature of the insulating material. The allowable temperature of the insulating material is the allowable temperature of the motor; the life of the insulating material is generally the life of the motor.
The ambient temperature varies with time and place. When designing the motor, it is stipulated that 40 degrees Celsius is taken as the standard ambient temperature in my country. Therefore, the allowable temperature of the insulating material or motor minus 40 degrees Celsius is the allowable temperature rise,
The allowable temperature of different insulating materials is different. According to the allowable temperature, the commonly used insulating materials for motors are A, E, B, F, and H. Calculated at an ambient temperature of 40 degrees Celsius, the five insulating materials and their allowable temperatures and allowable temperature rises are shown in the table below:
Class Insulation Material Allowable Temperature Allowable Temperature Rise
A Impregnated cotton, silk, cardboard, wood, etc., ordinary insulating paint 105 65
E Epoxy resin, mylar, green paper, tri-acid fiber, highly insulating paint 120 80
B Mica, asbestos, and glass fiber compositions using organic paints with improved heat resistance as binders 130 90
F Mica, asbestos and fiberglass compositions bonded or impregnated with epoxy resins with excellent heat resistance 155 115
H Mica, asbestos or fiberglass compositions bonded or impregnated with silicone resins, silicone rubber 180 140
★How to measure the phase angle of brushless motor?
Answer: Turn on the power of the controller, and the controller will supply power to the Hall element, then the phase angle of the brushless motor can be detected. The method is as follows: use the +20V DC voltage range of the multimeter, connect the red test lead to the +5V line, and the black pen to measure the high and low voltages of the three leads respectively, and compare them with the commutation table of the 60-degree and 120-degree motors.
