Brief analysis on the type selection of the hottes

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Brief analysis of motor brake selection

to select a suitable load of electric test platform, we first need to understand the characteristics and working principle of various types of load brakes:

first, eddy current brake

eddy current brake is an advanced domestic analog loading equipment, which is mainly used to simulate the output performance of various power devices, consisting of induction disk, armature and excitation parts. When the excitation coil assembled coaxially with the rotor is energized with DC, the magnetic flux generated by it forms a closed loop through the armature body, vortex ring, air gap and rotor. Since the outer circular surface of the rotor is made into evenly distributed teeth and grooves, a dense alternating magnetic field is generated in the air gap and the surface of the armature body or vortex ring. Therefore, when the rotor is dragged and rotated, the magnetic field at any point on the inner surface of the armature body and vortex ring changes, thereby inducing "vortex". Under the coupling action of "vortex" and magnetic field, braking torque is generated on the rotor. Since the armature hd=100- l/0.025 is fixed on the base plate through the base, the rotor cannot drive the armature to rotate, and the power output of the power machinery is converted into the equivalent heat generated by the "eddy current" on the armature and the eddy current ring, which is consumed by the continuous cooling water entering the armature and the eddy current ring cooling water tank and the eddy current brake itself. Corresponding to each constant current of the excitation coil, the eddy current brake shows a stable braking characteristic curve in which the torque depends on the speed. By changing the magnitude of the excitation current, the braking torque can be changed

II. Magnetic powder brake

magnetic powder brake is a new transmission element that uses magnetic powder as the medium and forms a magnetic powder chain to transmit torque when powered on. It is composed of inner rotor, outer rotor, exciting coil and magnetic powder. When the coil is not energized, the driving rotor rotates. Due to the centrifugal force, the magnetic particles are thrown on the inner wall of the driving rotor. There is no contact between the magnetic particles and the driven rotor, and the driving rotor idles. After the DC power is connected, an electromagnetic field is generated, and the magnetic particle of the working medium forms a magnetic particle chain under the action of the magnetic line of force, connecting the inner rotor and the outer rotor, so as to achieve the purpose of transmitting and braking torque. It can transmit a certain torque when it is independent of slip, and has the advantages of fast response, simple structure, no pollution, no noise, no impact and vibration. Because the company has the professional knowledge and energy of producing 3D printing consumables in a large range

III. hysteresis brake

the hysteresis brake is composed of two parts: the rotor and the stator pole. The rotor is made of special hysteresis materials. There is a certain gap in the stator pole, and the rotor rotates in the gap. When the coil is energized, a magnetic field is generated in the gap, resulting in the hysteresis effect of the rotor. When the hysteresis rotor rotates against the hysteresis force under the action of external force, the zigzag performance shall be in accordance with ASTM D790 standard; The impact performance test is carried out on the cantilever impact testing machine to generate the rated torque. The torque is only related to the magnitude of the exciting current and has nothing to do with the speed, so as to realize non-contact torque transmission

IV. servo motors

servo motors are divided into DC and AC servo motors, which can control speed and position with high accuracy, and convert voltage signals into torque and speed to drive the control object. The rotor speed of the servo motor is controlled by the input signal and can respond quickly. In the automatic control system, it is used as the actuator, and has the characteristics of small electromechanical time constant, high linearity, starting voltage, etc. it can convert the received electrical signal into the angular displacement or angular speed output on the motor shaft. Its main feature is that when the voltage signal is zero, there is no rotation phenomenon, and the speed decreases uniformly with the increase of torque

v. how to select the type

secondly, it is necessary to select the appropriate load according to the speed, torque, power and other attributes of the tested motor and the above load suitable scenarios. Each type of load has its own advantages and disadvantages:

1 Eddy current is suitable for high-speed and high-power occasions, and the maximum speed can support 30000rpm at 5kW

2. Magnetic particle braking is low-cost and is mainly used in low-speed and high-power occasions, but heat dissipation needs to be considered, with low accuracy and zero drift

3. The hysteresis brake is suitable for high-speed and low-power occasions. The torque range is very small. The maximum power of about 5kW can only be measured at 30n m;

4. Servo motor is suitable for occasions with high accuracy requirements, with good test repeatability, and supports energy fed loads. The range of speed and torque is not fixed, and the corresponding load can be flexibly selected according to the characteristics of the tested motor, so as to change the deepening of the overall aspect of the experimental machine from tools

therefore, according to the test requirements of the tested motor, the load brake is selected by comparing the characteristics of various types of loads

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