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Stepper Motors,Stepper Motor Drivers,Servo Motors-Jiangsu Novotech Electronic Technology Co., Ltd

Contact Person:sherry

0510-85389006

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0510-85389002

Address:A1-606,Tian'an Intelligent Park,No.228,Linhu Road, New District,Wuxi,Jiangsu,China

Stepper Motor FAQ

 1.What is stepper motor?

    Stepper motor is an actuator that converts electrical pulses into angular displacements.When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle (and stepping angle) by set direction. You can control the number of pulses to control the angular displacement, then achieve the purpose of accurate positioning; At the same time you can control the pulse frequency to control the motor speed and acceleration.

  2.Stepper Motor kinds

  There are three kinds of stepper motor:Permanent magnet(PM), reactive (VR) and hybrid (HB)

  PM type is generally two-phase, torque and volume is small, the stepping angle is generally 7.5 degrees or 15 degrees;

    VR type is generally three-phase, can achieve large torque output, step angle is generally 1.5 degrees, but the noise and vibration are great;

     HB type is mixed the advantage of PM and VR. It has two-phase and five-phase: two-phase step angle is generally 1.8 degrees and five-phase step angle is generally 0.72 degrees. This stepper motor is the most widely used.

  3.What is HOLDING TORQUE?

    Hold torque refers to the stator lock rotor torque,as the stepper motor power is turned on, but no rotation. It is one of the most important parameters of stepper motor, and the torque of the stepper motor at low speed is usually close to the holding torque. As the output torque of the stepper motor is decline by the speed increasing and the output power also changes by the speed,so the holding torque becomes one of the most important parameters of stepper motor. For example, when people say stepper motor of 2N.m , they means a stepper motor with a holding torque of 2N.m.

  4.What is DETENT TORQUE?

  DETENT TORQUE means the torque of the stator locks the rotor when powered off.

   As the material of VR stepper motor is not permanent magnet,it does not have DETENT TORQUE.

  5.Stepper motor's accuracy,is it cumulation?

  The precision of the stepper motor is 3% to 5% of the stepping angle and does not accumulate.

  6.How much temperature of the stepper motor appearance is allowed?

    Stepping motor temperature is too high will first demagnetize the magnetic material,resulting in the torque decline and even lost step, so the surface allowed maximum temperature depends on the magnetic demagnetization point of different material;the demagnetization point are usually more than 130 degrees, and some even reach to 200 degrees , so the stepper motor's surface temperature reach to 80 to 90 degrees is normal.

  7.Why the torque of the stepping motor will decrease by increasing speed?

    When the stepping motor rotates, the inductance of each phase  will form a reverse electromotive force; the higher the frequency, the greater the reverse electromotive force. In its role, the motor's current decreases by the frequency (or speed) increases, and then result torque decrease.

  8.Why stepper motor can run normally at low speed, but if at a very high speed,it can not start, and accompanied by howling?

    Stepper motor has a technical parameter: no-load start frequency means the normal pulse frequency of stepper motor when start with no-load, if the pulse frequency is higher than the value,the motor can not start normally, may lost step or stalled. The starting frequency should be lower when have load. If you want to make the motor to achieve high-speed rotation, the pulse frequency should be accelerated process, that means the starting frequency is low, and then rise to high frequency by a certain acceleration(from low speed to high speed).

  9.How to overcome the vibration and noise of two - phase hybrid stepping motor at low speed?

  A.If stepper motor just work in the resonance zone, by changing the gear ratio and other mechanical transmission to avoid the resonance zone;

  B.Using the drive with subdivision function, this is the most commonly and easiest way;

  C.Use the stepping motor with smaller stepping angles, such as three-phase or five-phase stepper motors;

  D.Replaced by AC servo motor, can almost completely overcome the vibration and noise, but the cost is high;

  E.Add magnetic damper in the motor shaft, but the mechanical structure changes a lot.

  10.Does the subdivision of the 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 stepper motor low-frequency vibration, improve the motor operating accuracy is only an add-function. For example, a two-phase hybrid stepping motor with a step angle 1.8 degree, if the subdivision of the drive is set 4, then the motor's operating resolution is 0.45 degree per pulse. If the accuracy of the motor can reach or near 0.45 degree, that depends on the subdivision current control accuracy of drive and other factors. The subdivision drive accuracy of different manufacturers may vary widely; As the subdivision more big,the accuracy is more difficult to control. 

  11.How to determine the DC power supply of stepper driver?

  A.Determination of voltage: power supply voltage of hybrid stepper motor driver is usually a wide range (eg.supply voltage of IM483 is 12 to 48VDC). the power voltage is usually choosed according to motor speed and response requirements. If the motor is operating at a high speed or quick responsive, the voltage is high.But should notice that the ripple of the supply voltage can not exceed the maximum input voltage of the driver,or it will damage the driver.

  B.Determination of current: The power current is usually determined by the output phase current I of the driver. If using linear power supply, the power current is usually choose 1.1 to 1.3 times of I; if using switching power supply, the power current is usually choose 1.5 to 2.0 times of I.

  12.What circumstances does the off-line signal FREE of hybrid stepper motor driver use?

    When the off-line signal FREE in low level, the current of the driver output to the motor is cut off, the motor rotor is in a free state (offline). In some automation equipments, if need rotate the motor shaft directly(by manual),as the drive is powered on, you can set low FREE signal to keep the motor off-line, then doing manual operation or adjustment. After manual completion, set the FREE signal high to doing continue automatically control.

  13.How to adjust the direction of the two-phase stepper motor?

  Only need to reverse the connection wire A+ and A-(or B+ and B-).

    About the drive subdivision principle and some instructions:

    In foreign countries,mainly use two-phase hybrid stepper motor and matched subdivision drive for the stepper system.

  The subdivision is mainly using to improve the motor performance.Description as follows: Stepping motor subdivision control is achieved by the driver precisely control the stepper motor phase current.For example, if the motor rated phase current is 3A, and use conventional drivers (constant current chopping mode) to drive the motor, the current in the winding will change from 0 to 3A or 3A to 0 for every step of motor, phase current changes so grate, it will cause vibration and noise of motor. But if use subdivision driver to drive the motor in a 10 subdivision state, the current in the winding only changes 0.3A instead of 3A, and with sinusoidal curve, which grately reduced the motor vibration and noise. so the performance advantage is the real advantage of subdivision. As the subdivision drive need to accurately control the motor phase current, so the drive should have a very high technical and process requirements, the cost will be higher. Note that there are some domestic drive use "smooth" to replace the subdivision, and also named subdivision, but they are not same, hope many users to see the different natures between them:

  1."Smooth" does not mean precisely control of the motor phase current, it means current rate change slow, so "smooth"does not produce micro-step, but subdivision of the micro-step can be used to accurately locate.

  2.The motor torque will deline after the motor phase current changes smooth,but subdivision control will cause the motor torque increase instead deline.