• 8 common sense of DC brushless motor

    8 common sense of DC brushless motor, the content is as follows:

    1. Before disassembling, use compressed air to blow off the dust on the motor surface and wipe off the surface dirt.

    2. Select the working location where the motor is disassembled and clean up the site environment.

    3. Familiar with motor structure characteristics and maintenance technical requirements.

    4. Prepare the tools (including special tools) and equipment needed to disassemble.

    5. In order to further understand the defects in the operation of the DC brushless motor, it is possible to do an inspection test before disassembly. To this end, the motor is loaded with a load test, and the temperature, sound, vibration, etc. of each part of the motor are inspected in detail, and the voltage, current, speed, etc. are tested, and then the load is disconnected, and a no-load inspection test is performed separately, and the test is performed. Record current and no-load loss.

    6. Cut off the power supply, remove the external wiring of the motor, and make a record.

    7. Test the motor insulation resistance by using a megohmmeter of suitable voltage. In order to compare the insulation resistance value measured at the time of the previous inspection to determine the change trend of the insulation of the motor and the insulation state, the insulation resistance value measured at different temperatures should be converted to the same temperature, generally converted to 75 °C.

    8. Test the absorption ratio K. When the absorption ratio is greater than 1.33, it indicates that the motor insulation is not damp or the degree of moisture is not serious. In order to compare with the previous data, the absorption ratio measured at any temperature is also converted to the same temperature.

  • Motor bearing fault repair method

    The rotating shaft is rotated by the bearing support, which is the heaviest part of the load and is a component that is easy to wear.

    (1) Fault check

    In-service inspection: When the rolling bearing has less oil, it will emit an abnormal sound. A slight regular "card, card" sound may be a broken ball. If there is debris such as sand in the bearing, noise will appear.

    Check after disassembly: check the bearing for signs of wear, then pinch the inner ring of the bearing and lay the bearing flat. The other hand pushes the outer steel ring hard. If the bearing is good, the outer steel ring should rotate smoothly and rotate. There is no vibration and obvious stuck phenomenon, such as the phenomenon that the bearing does not reverse after the bearing stops, indicating that the bearing has been scrapped and needs to be replaced in time. The left hand is stuck on the outer ring, the right hand pinches the inner steel ring, and then the bearing is axially pushed. There is looseness or swaying phenomenon, which is serious wear.

    (2) Troubleshooting

    The rust spots on the bearing surface are sanded with an abrasive cloth and then cleaned with gasoline: or when the bearing is cracked or excessive wear occurs, it should be replaced in time. When replacing a new bearing, make sure that the new bearing model meets the requirements.

  • Motor classification

    First, the general motor classification details

    Synchronous motor

    Can also be divided into permanent magnet synchronous motor, reluctance synchronous motor and hysteresis synchronous motor.

    2. Asynchronous motor

    Can be divided into induction motor and AC commutator motor.

    3. Induction motor

    It is also divided into three-phase asynchronous motor, single-phase asynchronous motor and shaded-pole asynchronous motor.

    4. AC commutator motor

    It is divided into single-phase series-excited motor, AC/DC dual-purpose motor and repeller motor.

    5. DC motor

    According to the structure and working principle, it can be divided into brushless DC motor and brushed DC motor.

    6. Brushed DC motor

    Can be divided into permanent magnet DC motor and electromagnetic DC motor. The electromagnetic DC motor is further divided into a series-excited DC motor, a shunt DC motor, a separately excited DC motor and a compound excitation DC motor. The permanent magnet DC motor is further divided into a rare earth permanent magnet direct current motor, a ferrite permanent magnet direct current motor and an aluminum nickel cobalt permanent magnet direct current motor.

    Second, according to the start and operation mode

    According to different starting and running modes of the motor, it can be divided into a capacitor-starting single-phase asynchronous motor, a capacitor-operated single-phase asynchronous motor, a capacitor-starting single-phase asynchronous motor, and a split-phase single-phase asynchronous motor.

    1. Classification by use can be divided into drive motor and control motor

    The drive motor is divided into electric tools (including tools for drilling, polishing, polishing, slotting, cutting, reaming, etc.) with electric motors and household appliances (including washing machines, electric fans, refrigerators, air conditioners, tape recorders, video recorders, DVDs). Motors, vacuum cleaners, cameras, hair dryers, electric shavers, etc.) Motors for motors and other general purpose small mechanical equipment (including various small machine tools, small machines, medical equipment, electronic equipment, etc.).

    Third, the control motor

    Also divided into stepper motors and servo motors.

    1. Classification by rotor structure

    According to the structure of the motor according to the rotor, it can be divided into a cage type induction motor (the old standard is called a squirrel cage type asynchronous motor) and a wound rotor induction motor (the old standard is called a wound type asynchronous motor).

    2. Classified by operating speed

    According to different operating speeds of motors, they can be divided into high-speed motors, low-speed motors, constant-speed motors, and speed-regulating motors.

    Low-speed motors are further classified into gear reduction motors, electromagnetic reduction motors, torque motors, and claw-pole synchronous motors.

    In addition to the stepless constant speed motor, the stepless constant speed motor, the stepless variable speed motor and the stepless variable speed motor, the speed regulating motor can also be divided into an electromagnetic speed regulating motor, a DC speed regulating motor, a PWM variable frequency speed regulating motor and Switched reluctance motor.

    The rotor speed of an asynchronous motor is always slightly lower than the synchronous speed of the rotating magnetic field. The rotor speed of the synchronous motor is always kept at the synchronous speed regardless of the load.

  • General principle of servo motor drive (2)

    Talk about the impact of PID on the difference adjustment system:

    1. The individual P (proportion) is the proportional operation of the difference. Its remarkable feature is that there is a difference adjustment. The difference is that after the adjustment process is finished, the adjusted quantity cannot be exactly equal to the set value. There must be a residual between them. The specific value of the residual can be calculated by the proportional relationship. Increasing the ratio will effectively reduce the residual and increase the system response, but it will easily lead to severe shock or even instability of the system.

    2. The separate I (integral) is to make the change speed of the output signal of the regulator proportional to the difference signal. It is not difficult to understand that if the difference is large, the rate of change of the integral link is large, and the ratio of the proportional constant of this link is large. The reciprocal we usually call it the integral time constant in the servo system. The smaller the integral time constant means the faster the system changes, so if the integral speed is increased (that is, the integral time constant is reduced), the control system will be reduced. The degree of stability until the end of the divergence of the shock process, the biggest advantage of this link is that the final adjustment is no residual.

    3, PI (proportional integral) is the advantage of combining P and I, using P to quickly offset the effects of interference, while using I to eliminate residuals.

    4. The individual D (differential) is adjusted according to the direction and size of the difference. The output of the regulator is proportional to the derivative of the time. The differential link can only play an auxiliary adjustment role. It can be adjusted with other adjustments. The advantage of combining it with PD and PID adjustment is that it can be adjusted according to the speed of change of the adjusted amount (difference), instead of waiting for a large deviation to start, it is to give the regulator some degree. Predictability can increase the response characteristics of the system to small changes.

    5, PID integrated role can make the system more accurate and stable to achieve control expectations.

    The PID constant of the servo current loop is generally set inside the driver, and the user does not need to change it.

    The speed loop mainly performs PI (proportional and integral), and the ratio is the gain, so we need to adjust the speed gain and the speed integral time constant to achieve the desired effect.

    The position loop mainly performs P (proportional) adjustment, so we only need to set the proportional gain of the position loop.

    There is no fixed value for the parameter adjustment of the position loop and speed loop. It depends on the mechanical transmission connection mode of the external load, the movement mode of the load, the load inertia, the speed and acceleration requirements, and the rotor inertia and output inertia of the motor itself. It is decided that the simple method of adjustment is to adjust the gain parameter from small to large in the range of general experience according to the external load, and the integral time constant is from large to small, so that the steady state value without vibration overshoot is the optimum value. Make settings.

    When the position mode needs to adjust the position loop, it is best to adjust the speed loop first (the proportional gain of the position loop is set at the minimum value of the empirical value). After the speed loop is stabilized, the position loop gain is adjusted, and the appropriate amount is gradually increased. The response of the position loop is preferably slower than the speed loop, otherwise the speed shock is prone to occur.

  • General principle of servo motor drive (1)

    Give another relevant example. If the process of processing data is intelligent, then those power-intensive production processes will be discovered and cancelled. These applications can reduce the cost of the company by up to 80%. Therefore, we can say that Industry 4.0 has created a blueprint for the entire networked production. In this blueprint, the machine manages itself through the entire value chain, scheduling machines and raw materials, and delivering the products directly to consumers.

    If Europe wants to have a high starting point in the future market, it must lay the foundation from now on. The motion servo is generally a three-loop control system, and the current loop speed loop position loop from the inside to the outside.

    1. First, the current loop: the input of the current loop is the output of the speed loop PID adjustment. We call it “current loop reference”, then the current loop is given and the “current loop feedback” value is compared. The difference is the PID adjustment output to the motor in the current loop. The "current loop output" is the phase current of each phase of the motor. The "current loop feedback" is not the encoder feedback but is installed in the driver inside each phase. The Hall element (magnetic field induction becomes a current voltage signal) is fed back to the current loop.

    2. Speed loop: The input of the speed loop is the output of the position loop PID adjustment and the feedforward value of the position setting. We call it “speed setting”, and this “speed setting” and “speed loop feedback” value are compared. After the difference is made in the speed loop for PID adjustment (mainly proportional gain and integral processing), the output is the "given loop given" mentioned above. The feedback of the speed loop is derived from the feedback value of the encoder via the "speed operator".

    3. Position loop: The input of the position loop is an external pulse (normally, the servo exception is directly written to the address of the drive), and the external pulse is subjected to smoothing processing and electronic gear calculation as the "position loop setting". The calculated value of the pulse signal from the encoder feedback and the deviation counter is calculated after the PID adjustment of the position loop (proportional gain adjustment, no integral derivative) and the value of the feedforward signal given by the position. The given speed loop is given above. The feedback of the position loop also comes from the encoder.

    The encoder is mounted on the tail of the servo motor. It has no connection with the current loop. It samples the rotation of the motor instead of the motor current, and has no connection with the input, output and feedback of the current loop. The current loop is formed inside the driver. Even if there is no motor, a feedback loop can be formed by installing an analog load (such as a bulb) current loop on each phase.

  • How to judge the difference between the servo motor and the servo drive?

    Look at the error, alarm number on the drive, and then check the manual. If there is no alarm, then it is naturally a drive failure. Of course, it is possible that there is no fault in the fundamental servo, but the control signal is wrong and the servo is not working.

    In addition to looking at the error on the drive, the alarm number, and then check the manual, sometimes the most direct way to judge is to replace, such as X and Z-axis servo change (the same model can be used). Or modify the parameters, such as locking the X axis, so that the system does not detect the X axis, but it should be noted that the X axis is interchangeable with the Z axis. Even if the model is the same, the imported device may have problems due to different loads and different parameters. Of course, if it is a domestic device, the servo parameters are usually not adjusted for the use, and there is generally no problem. However, it should be noted whether the X-axis and Z-axis motor power torque are the same, whether the motor screw is directly connected, and the electronic gear reduction ratio.