When we understand the hub motor, we often hear the word "Hall element". The hall element is the key component in the brushless hub motor. The quality of the hall element is directly related to the quality of the brushless wheel motor. So the role of the hall element is quite large. What is the function of the hall element of the brushless wheel motor? What kind of classification, today's global wind editor will give you an introduction.
1、 The function of Hall element
1. Control motor rotation
In brushless wheel motor, a rotating magnetic steel acts as a switch to control the magnetic flux. When the magnetic steel is close to the hall integrated circuit, the Hall voltage is large (on), the magnetic field deviates from the integrated chip, and the Hall voltage disappears (off). In this way, the change of the output voltage of Hall integrated circuit can indicate that the shaft is in a certain position. By using this working principle, the motor can be controlled to rotate.
2. Control motor speed
Hall element has the function of speed control switch in BLDCM. The rotation angle of rotary handle is converted from Hall element into variable digital voltage to variable digital voltage, so that the controller can adjust the brushless wheel motor and control the speed of motor. Electric cars are equipped with speedometer. Hall element measures the speed by calculating the number of electric vehicle wheel rotation cycles, and then directly displays the mileage or speed through the calculation instrument.
3. Change the direction of the current
Hall element is also used to change the direction of current in BLDCM. At present, brushless hub motor is the mainstream of motor structure, so the brush motor is gradually or eliminated. Hall element is used to replace the brush of motor in brushless hub motor, so the motor using Hall element must be brushless motor.
4. Strong signal output
The hall of BLDCM is a semiconductor sensor. Under the action of Lorentz force, the electron current will shift to one side when passing through the hall semiconductor, resulting in potential difference on the side of the plate, which is called Hall voltage. The Hall voltage changes with the change of magnetic field strength. The stronger the magnetic field is, the higher the voltage is. On the contrary, the Hall voltage value is very small, usually only a few millivolts, but the voltage can be amplified enough to output a strong signal by the amplifier in the integrated circuit.
2、 Classification of Hall elements
According to the function of Hall elements, they can be divided into hall linear devices and Hall switch devices.
1. Hall switch device
Hall switch device outputs digital quantity. According to the induction mode of Hall switches, they can be divided into unipolar Hall switches, bipolar Hall switches and full polarity Hall switches.
(1) The induction mode of unipolar Hall switch: a magnetic pole of the magnetic field is close to it and outputs a low potential voltage or off signal, and the magnetic pole of the magnetic field leaves it to output a high potential voltage or on signal. However, it should be noted that the monopolar Hall switch will specify a magnetic pole induction to be effective. Generally, the positive induction magnetic field s pole and the reverse induction N-pole.
(2) Induction mode of bipolar Hall switch: because the magnetic field has two magnetic poles, positive and negative, the two magnetic poles respectively control the opening and closing of the bipolar Hall switch. It generally has the function of locking, that is, when the magnetic pole leaves, the Hall output signal does not change until the other magnetic pole is induced. In addition, the initial state of bipolar Hall switch is random output, which may be high level or low level.
(3) Induction mode of full polarity Hall switch: the induction mode of full polarity Hall switch is similar to that of unipolar Hall switch. The difference is that unipolar Hall switch will specify magnetic pole, while full polarity Hall switch will not specify magnetic pole. Any magnetic pole is close to the output low-level signal, leaving the output high-level signal.
2. Hall linear device
Linear Hall element is a kind of magnetic sensor with analog signal output. The output voltage varies linearly with the input magnetic density. The voltage output of linear Hall effect sensor can accurately track the change of magnetic flux density. In the absence of magnetic field, theoretically, the output should be equal to half of the supply voltage in the operating voltage and temperature range. Increasing the Antarctic magnetic field will increase the voltage from its static voltage. Conversely, increasing the Arctic magnetic field will increase the voltage from its static voltage. These components measure current angle, proximity, motion and magnetic flux. They can reflect mechanical events in a magnetically driven manner.
The above content is about the function of Hall element in BLDCM. In addition, it is added that hall element can be divided into hall linear device and Hall switch device according to function classification. In a word, Hall element plays an important role in hub motor and is an indispensable part.
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