Most of the motor knowledge you want is here, and the necessary knowledge of motors is shared.
When purchasing a motor, users will encounter a variety of problems, such as parameters, installation, maintenance and so on. Today, the editor has synthesized several common problems encountered by users for your reference. These problems are not only limited to micro DC motors, but also have motor problems such as ordinary motors, aluminum shell motors, variable frequency motors, and three-phase asynchronous motors.
01 What is the reason why the leakage circuit breaker is easy to trip when using the inverter?
The waveform output by the inverter will have high-order harmonics, but the motor and the cable between the inverter and the motor will generate leakage current. This current will be much larger than that when the motor is driven by the power frequency, so a tripping phenomenon will occur. Since the leakage current output by the inverter is about 3 times that of the power frequency current, plus the leakage current of the motor, etc., the current of the leakage protector should be selected to be about 10 times greater than the power frequency current.
02 Is it necessary to use a variable frequency motor when using a motor for variable frequency speed regulation experiments?
If you are doing frequency conversion speed regulation experiments, you do not have to use frequency conversion motors, ordinary AC motors and DC motors can also be used.
AC variable frequency motor is actually a motor that adjusts the speed by adjusting the frequency of the AC power, mainly by the frequency converter. Note: The motor itself will not be frequency-converted, and an ordinary motor plus a frequency converter can be used to achieve frequency conversion.
The frequency conversion of DC motors is different. Take DC motor inverter air conditioners as an example: by converting the power frequency AC motor into DC power, and then sending it to the power module, the model is controlled by a microcomputer, and the controlled DC power is sent to the DC motor of the compressor to control the compressor. The displacement realizes variable frequency speed regulation.
03 What is the function of the reducer?
Reduce the output speed of the motor and increase the data torque.
04 The reason for the slow speed when the motor starts?
There are two situations. The first is that the speed is normal at startup after slow start, then the startup capacitor may not match; or the motor design is like this (the motor design is different in different applications); it may also be caused by too much load resistance. Startup time is too long.
The second situation is that the speed is still very slow after starting, so factors such as insufficient voltage, mismatched capacitors, and large rotational resistance need to be considered.
05 How to choose the brush of asynchronous motor?
First of all, it is necessary to know whether the working conditions of the brush can meet the current density and the linear velocity of the peripheral edge of the collector ring, which can be determined by the formula:
Brush current carrying capacity = brush current density × brush width × brush thickness ≥ motor rotor rated current
The linear speed of the peripheral edge of the collector ring = the rated speed of the motor × the circumference of the collector ring ≤ the specified range for the brush
Brushes generally include graphite brushes, metal brushes, electrochemical graphite brushes, etc. During use, attention should be paid to frequently check the brush activity, brush pressure and degree of wear. The brush should be able to move up and down freely in the brush holder without jamming. When the brush is stuck, smooth both sides of the brush on the emery cloth. The pressure of the brush should be adjusted appropriately according to the type and model of the brush. At present, most of the brush compression springs attached to the brush holder are tension and compression springs, and their pressure gradually decreases with the wear of the brushes. Therefore, during the operation of the motor, the brush pressure should be adjusted at any time.
06 60HZ motor is used on 50Hz power supply, what should I pay attention to?
This is because the current frequency of the motor is lower than the design frequency. To reduce the no-load back electromotive force generated during the rotation and increase the no-load current, which will cause damage to the motor, the no-load voltage is required to be reduced.
In the variable frequency speed regulation technology, the frequency of the motor and the voltage of the stator are changed at the same time. That is, when the frequency drops, the voltage also drops at the same time, so that the motor will not be over-current, and the ideal operating effect will be obtained.
07 Why should an output reactor be added to the output end of the inverter, and what is its function?
The output reactor is added at the output end of the inverter to increase the wire distance from the inverter to the motor. The output reactor can effectively suppress the instantaneous high voltage generated when the IGBT of the inverter switches on and off, and reduce the adverse effects of this voltage on cable insulation and motor.
The main function of the reactor is to limit the capacitive charging current of the motor connection cable and limit the voltage rise rate on the motor winding within 540V/μs. It is also used to passivate the output voltage (switching frequency) of the inverter. to reduce the disturbance and impact of power components (such as IGBTs) in the inverter.Most of the motor knowledge you want is here, and the necessary knowledge of motors is shared.
When purchasing a motor, users will encounter a variety of problems, such as parameters, installation, maintenance and so on. Today, the editor has synthesized several common problems encountered by users for your reference. These problems are not only limited to micro DC motors, but also have motor problems such as ordinary motors, aluminum shell motors, variable frequency motors, and three-phase asynchronous motors.
