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1. What is a permanent magnet stepper motor?
Permanent magnet stepper motor is an actuator that converts electrical pulses into angular displacements. It is popular to say that when the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle (and stepping angle) in the set direction. You can control the number of pulses to control the angular displacement, so as to achieve the purpose of accurate positioning;
At the same time you can control the pulse frequency to control the motor speed and speed of rotation, so as to achieve the purpose of speed.
What kind of stepper motor?
Stepper motor is divided into three kinds: permanent magnet (PM), reactive (VR) and hybrid (HB)
Permanent magnet step is generally two-phase, torque and volume is small, the stepping angle is generally 7.5 degrees or 15 degrees;
Reaction step is generally three-phase, can achieve large torque output, step angle is generally 1.5 degrees, but the noise and vibration are great. In Europe and the United States and other developed countries 80 years have been eliminated;
The mixed step is the advantage of mixing the permanent magnet and the reactive. It is divided into two-phase and five-phase: two-phase step angle is generally 1.8 degrees and five-step steep angle is generally 0.72 degrees. This stepper motor is the most widely used.
3. What is the holding torque (HOLDING TORQUE)?
Hold torque (HOLDING TORQUE) refers to the stepper motor power is turned on, but no rotation, the stator lock rotor torque. It is one of the most important parameters of the stepper motor, and the torque of the stepper motor at low speed is usually close to the holding torque. Since the output torque of the stepper motor is constantly attenuated with increasing speed and the output power also changes with increasing speed, keeping the torque becomes one of the most important parameters to measure the stepper motor. For example, when people say that the 2N.m stepper motor, in the absence of special instructions, means a stepper motor with a torque of 2N.m.
4. What is DETENT TORQUE?
DETENT TORQUE is the case where the stator locks the rotor torque when the stepper motor is not energized.
DETENT TORQUE in the country there is no uniform way of translation, easy to make people misunderstand; because the reactive stepper motor rotor is not permanent magnet material, so it does not DETENT TORQUE.
5. What is the precision of the stepper motor?
The precision of the stepper motor is 3-5% of the stepping angle and does not accumulate.
6. How much does the temperature of the stepper motor allow?
Stepping motor temperature is too high will first demagnetize the magnetic material of the motor, which leads to the decline in torque and even out of step, so the maximum allowable motor surface temperature depends on the demagnetizing point of different motor magnetic materials;
In general, the demagnetization of magnetic materials are more than 130 degrees Celsius, and some even up to 200 degrees Celsius, so the stepper motor surface temperature at 80-90 degrees Celsius is completely normal.
7. Why is the torque of the stepping motor decreasing as the speed increases?
When the stepping motor rotates, the inductance of each phase winding of the motor will form a reverse electromotive force; the higher the frequency, the greater the reverse electromotive force. In its role, the motor with the frequency (or speed) increases and phase current decreases, resulting in decreased torque.
8. Why stepper motor can run normally at low speed, but if higher than a certain speed can not start, and accompanied by howling
Stepper motor has a technical parameter: no-load start frequency, that is, stepper motor in the case of no-load can start the normal pulse frequency, if the pulse frequency is higher than the value of the motor can not start normally, may occur stealing or stall. In the case of a load, the starting frequency should be lower. If you want to make the motor to achieve high-speed rotation, the pulse frequency should be accelerated process, that is, the starting frequency is low, and then according to a certain acceleration to the desired high frequency (motor speed from low speed to high speed).
9. How to overcome the two-phase hybrid stepper motor in the low-speed operation of the vibration and noise?
Stepper motor low-speed rotation vibration and noise is its inherent shortcomings, generally can be used to overcome the following:
A. If the stepper motor is just working in the resonant area, the resonant area can be avoided by changing the mechanical transmission such as the reduction ratio;
B. The use of subdivision function with the drive, which is the most commonly used, the easiest way;
C. into a step angle smaller stepper motor, such as three-phase or five-phase stepper motor;
D. replaced by AC servo motor, almost completely overcome the vibration and noise, but the cost is higher;
E. In the motor shaft plus magnetic damper, the market has this product, but the mechanical structure changes greatly.
10. Does the breakdown of a subdivision drive represent accuracy?
Stepping motor subdivision technology is essentially an electronic damping technique (please refer to the literature), the main purpose is to reduce or eliminate the low-frequency stepper motor vibration, improve the motor operating accuracy is only a sub-technology with the function. For example, for a two-phase hybrid stepping motor with a step angle of 1.8 °, if the subdivision of the subdivided drive is set to 4, then the motor's operating resolution is 0.45 ° per pulse and the accuracy of the motor can be reached or near 0.45 °, also depends on the subdivision drive subdivision current control accuracy and other factors. Different manufacturers of subdivision drive accuracy may vary widely; the greater the precision of the more difficult to control.
11. What is the difference between the four-phase hybrid stepper motor and the serial connection and parallel connection of the drive?
Four-phase hybrid stepper motor is generally driven by two-phase drive, so the connection can be used to connect or parallel connection four-phase motor connected into two-phase use. Series connection method is generally used in the case of the motor speed, the drive output current required for the motor phase current of 0.7 times, so the motor heat is small; parallel connection method is generally used in the case of high motor speed (also known as high-speed connection ), The required drive output current is 1.4 times the motor phase current, and thus the motor heat is large.
12. How to determine the stepper motor drive DC power supply?
A. Determination of voltage
The power supply voltage of the hybrid stepper motor driver is generally a wide range (such as the supply voltage of the IM483 is 12 ~ 48VDC). The supply voltage is usually selected according to the working speed and response requirements of the motor. If the motor is operating at high speed or responsive, the voltage is also high, but note that the ripple of the supply voltage can not exceed the maximum input voltage of the driver. Otherwise, the drive may be damaged.
B. Determination of current
The power supply current is generally determined by the output phase current I of the driver. If the use of linear power supply, power supply current generally desirable I 1.1 ~ 1.3 times; if the use of switching power supply, power supply current generally desirable 1.5 to 2.0 times.
13. Are the off-line signals of the hybrid stepper motor drive FREE under what circumstances?
When the off-line signal FREE is low, the drive output to the motor current is cut off, the motor rotor is in a free state (offline). In some automation equipment, if the drive is not required in the case of direct rotation of the motor shaft (manual mode), you can put the FREE signal low, the motor off-line, manual operation or adjustment. After manual completion, and then FREE signal set high to continue to automatically control.
Permanent magnet stepper motor, recommended Shenzhen Zhengdezhi Control Co., Ltd., welcome to consult!