Vacuum | deep low temperature | high temperature | radiation resistance and automation solutions
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2022
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About stepper motors
All kinds of motors that we usually see have iron cores and winding coils inside. The winding has resistance, and the power will produce loss, the loss is proportional to the square of the resistance and current, which is what we often say copper loss, if the current is not the standard DC or sine wave, it will also produce harmonic loss; The core has a hysteresis eddy current effect, which will also produce a loss in the alternating magnetic field, and its size is related to the material, current, frequency, and voltage, which is called iron loss. Copper loss and iron loss will be manifested in the form of heat, thus affecting the efficiency of the motor. The stepper motor generally pursues positioning accuracy and torque output, the efficiency is relatively low, the current is generally large, and the harmonic component is high, and the frequency of current alternating also changes with the speed, so the stepper motor is generally heated, and the situation is more serious than the general AC motor.
2, why high and low temperature stepper motor, servo motor heating higher than ordinary motor?
The coil material of high and low temperature motor needs to withstand higher temperature and higher insulation strength, so the heat dissipation performance is worse than the coil of the general servo motor, but it will not affect the high temperature performance of the motor.
3, stepper motor heating changes with speed:
When the constant current drive technology is used, the current of the stepper motor is maintained constant at static and low speed to maintain a constant torque output. When the speed is high to a certain extent, the internal back potential of the motor increases, the current will gradually decrease, and the torque will also decrease. Therefore, the heat caused by copper damage is related to speed. Static and low speed heating is generally high, high speed heating is low. However, the change of iron loss (although the proportion is small) is not entirely true, and the heat of the motor is the sum of the two, so the above is just a general situation.
4, The effects of fever
Although the motor heating generally does not affect the life of the motor, most customers do not need to pay attention. However, it can bring some negative effects in severe cases. If the thermal expansion coefficient of each part of the motor is different, the change of structural stress and the small change of the internal air gap will affect the dynamic response of the motor, and the high speed will be easy to lose step. For example, some occasions do not allow excessive heat of the motor, such as medical devices and high-precision test equipment. Therefore, the heating of the motor should be controlled as necessary.
5, How to reduce motor heating:
To reduce heat is to reduce copper loss and iron loss. There are two directions to reduce copper loss, reduce resistance and current, which requires that the motor with small resistance and small rated current should be selected as far as possible in the selection of two-phase motors, which can be connected in series without parallel motors. However, this often contradicts the requirements of torque and high speed. For the motor that has been selected, it should make full use of the driver's automatic half-current control function and off-line function, the former automatically reduces the current when the motor is at static, the latter simply cuts off the current. In addition, because the current waveform of the subdivision driver is close to sine, the harmonics are less, and the motor will heat less. There are not many ways to reduce iron loss, and the voltage level is related to it. Although the high-voltage driven motor will bring the improvement of high-speed characteristics, it will also bring the increase of heat. Therefore, the appropriate driving voltage level should be selected, taking into account high-speed, stationary and heat, noise and other indicators.
Two, the accuracy of the stepper motor can reach how much?
1, KH, KVM series two-phase hybrid stepper motor the entire step Angle is 1.8° Step Angle accuracy is 1.8° 3 to 5%. This error is not cumulative, and only occurs when the stepper motor has just been powered on. This error will not occur again during motor operation.
2, our actual test: The AKD incremental encoder is installed in the rear end of the KH57 motor, the encoder rotates one turn to feedback 16384 counts, and the encoder feedback data received by the PLC is less than 2 feedback counts. Equivalent error is less than 360*(2/16384)=0.04° .
Three, Delta or Mitsubishi PLC stepper motor speed control:
1, Delta and Mitsubishi PLC pulse control stepper motor and servo motor with DPLSR/PLSR, this instruction is a pulse instruction with acceleration and deceleration, acceleration and deceleration time greater than 100ms.
,2, can not use the DPLSY/PLSY instruction, this instruction is not a pulse instruction with acceleration and deceleration, because the acceleration is too large, it will cause the stepper motor high-speed gridlock, lost step or servo motor overload alarm.
Four, how much is the standard length of the lead of the stepper motor? Can you extend it? What is the effect of lead extension on motor performance? What is the maximum extension?
1, KH stepper motor standard lead length of 3 meters, KVM stepper motor standard lead length of 1 meter.
2, The stepper motor leads can be extended up to 15 meters. More than 15 meters of motor leads will lead to reduced current and motor torque will be attenuated.
Five, how to choose the fine score of the stepper drive
We recommend a fine score of 4000 or 10000.
1, after testing at high speed, for the same motor speed, the motor output torque when choosing 10000 fine fraction is greater than the motor output torque when choosing 1000 fine fraction.
2, in addition, for some brands of PLC, when the subdivision is selected 1000, the motor vibration is very large at low speed (such as less than 10rpm), and the torque is very small. When the subdivision is selected at 10000, the low speed operation can be well met.
3, Fine fraction selection is also subject to the highest pulse frequency supported by the PLC.
Six, pulse and direction terminals need to add resistance.
Whether the pulse direction signal needs to be resistance depends on the voltage supported by the driver pulse and direction port.
1, if the voltage supported by the driver pulse and direction port is 24V, it is possible to use a 24V switching power supply to provide the drive voltage to the pulse and direction without external resistance.
,2, if the voltage supported by the driver pulse and direction port is 5V, an additional 2K resistor is required when the driver voltage is supplied to the pulse and direction using a 24V switching power supply.
Seven. Do ENA+, ENA- (or MF+, MF-) terminals on the drive need to be connected?
ENA+, ENA- (or MF+, MF-) for the stepper motor release signal, when the release motor signal terminal to provide effective power (generally make the corresponding optical coupling inside the driver), will turn off the motor phase current, motor shaft in a free state.
Eight, whether to use the semi-current function of the stepper driver
The stepper driver does not receive the command pulse signal at a certain time (such as 1.5S), and the phase current of the motor is automatically reduced to half of the set current to reduce the motor heat. Therefore, for the application of horizontal motion, it is recommended to open the half-current switch to reduce the motor heat, and it is recommended to close the half-current switch for vertical motion to ensure the holding torque when the motor is not working.
Nine, how to choose the working voltage of the stepper driver
The higher the power supply voltage of the stepper driver, the smaller the torque attenuation at high speed. Within the voltage range allowed by the stepper driver, it is recommended to choose as high a drive voltage as possible to improve the high-speed torque output of the stepper motor. However, the higher the voltage, the greater the heat of the stepper motor, the greater the vibration noise.
Ten, how to set the output current of the stepper driver
In general, the output current of the stepper driver is set to be no greater than the phase current of the motor. There are two exceptions:
1, if the selected motor output torque is slightly less than the required torque of the load, the electric driver output current can be set to slightly greater than the phase current of the motor (for example, the rated current is 2A, can be set to 2.5A or 3A). But the greater the current, the greater the heat of the motor.
2, when working in a low temperature environment, set the output current of the stepper motor driver to be slightly higher than the rated current of the stepper motor, in order to improve the output torque of the stepper motor.
Eleven, how to change the stepper motor rotation reverse
After the stepper motor is installed, if the actual rotation direction is opposite to the desired rotation direction, and it is not convenient to change the rotation direction of the motor by modifying the control program, you can change the rotation direction of the motor by exchanging the wiring sequence of the motor lead A+, A- (or exchange B+, B-) and the driver.
The three-phase stepper motor can be switched to any two phases of the three phases to achieve reverse.
Stepper motor heating,High and low temperature,How to reduce motor heating
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