The planetary gearbox is also called the gearbox.

It is also a mechanism that reduces the transmission ratio and at the same time increases the torque of the motor in proportion to the power.Planetary gearbox is a transmission mechanism.

It uses the speed sensor of the gearbox to reduce the number of revolutions of the motor to the required number of revolutions and obtain a large torque.

So, how does the planetary gearbox work?

We can learn more from the structure first.The main transmission structure of planetary gearbox is planetary gear, sun gear and ring gear.

The ring gear is in close contact with the internal gear.

The closed-loop stepping servo system, as an innovation of the traditional open-loop stepping system, provides a cost-effective choice for applications with higher safety, reliability or product quality requirements.

Install a position feedback device behind the stepper motor or form a closed loop like a servo system by means of some indirect parameter detection position, to check or control out of step, detect motor stalls, and ensure that the motor runs at a higher speed , Precision and greater effective torque output.

Greatly improve the effective torque and speed of the stepper motor, and further broaden the application range of the stepper motorUnder the same voltage and current control conditions, compared with the traditional open-loop stepping system, the closed-loop stepping servo system can run smoothly in the speed range of 0.1-3000RPM, and the effective torque is increased to more than 60% of the holding torque.

Realize high-speed and miniaturization of equipmenta.

High acceleration and deceleration response, high-speed precision positioningb.

System miniaturization Since the stepper motor has a larger torque at low speed, compared with a conventional servo motor, a larger continuous torque can be used in the low-speed rotation area, so the system size can be miniaturized.

Generally, stepper motors can achieve open-loop control, that is, the angle and speed of the stepper motors can be controlled through the number and frequency of pulses input from the signal input terminal of the driver, without feedback signals.

However, stepper motors are not suitable for long-term operation in the same direction, and it is easy to burn the product.

It is usually better to use short-distance and frequent actions during use.The stepper motor and the stepper motor driver constitute a stepper motor drive system.

The performance of the stepper motor drive system not only depends on the performance of the stepper motor itself, but also on the performance of the stepper motor driver. 

The gap between the stator and rotor of a brushless motor is called an air gap.

If the air gap is too large, the reluctance and excitation current are increased, thereby reducing the power factor of the brushless motor.

The air gap of small and medium motors is generally between 0.2~2.0mm.The air gap between the stator and rotor of a dc brushless motor has a great relationship with the performance of the motor.

The larger the air gap, the greater the magnetic resistance.

On the one hand, to generate the same rotating magnetic field, a larger excitation current is required.

At the same time, since the excitation current is a reactive current, the increase of the excitation current will make the power factor of the motor worse.

Stator aspect: the stator core becomes elliptical, eccentric, and loose; the stator winding is broken, ground breakdown, inter-turn short circuit, wiring error, and the stator three-phase current is unbalanced.2.

Rotor failure: the rotor core becomes elliptical, eccentric, or loose.

The rotor cage bar is unwelded with the end ring, the rotor cage bar is broken, the winding is wrong, the brush contact is poor, etc.Mechanical reason1.

Motor itself: unbalanced rotor, bent shaft, deformed slip ring, uneven air gap between stator and rotor, inconsistent magnetic center of stator and rotor, bearing failure, poor foundation installation, insufficient mechanical strength, resonance, loose anchor screw , the motor fan is damaged.2.

Coordination with the coupling: the coupling is damaged, the coupling is poorly connected, the coupling is not centered correctly, the load is unbalanced, and the system is resonant.Reasons for motor mixing1.

Motor vibration is often due to uneven air gap, causing unilateral electromagnetic tension, and unilateral electromagnetic tension further increases the air gap.

Drive voltageThe driving voltage refers to the input voltage of the stepper motor.

The selection of the voltage is related to the use environment of the machine.

It can be DC or AC.

The choice of voltage has a great influence on the performance of the stepper motor.

The higher the voltage, the better the performance of the stepper motor, especially the better the high-speed performance of the motor.

Drive currentThe driving current refers to the current at both ends of the single-phase winding of the stepper motor, also called the phase current.

The easiest way to distinguish whether a stepper motor is closed-loop or open-loop is to see if there is a feedback signal.

If there is a signal feedback, it is a closed-loop stepper motor, and if there is no signal, it is an open-loop stepper motor.The fundamental difference between a closed-loop stepper motor and an ordinary stepper motor is that the closed-loop motor has signal feedback, and the open-loop stepper motor has no feedback signal, only executes in order.

On the contrary, the closed-loop stepper motor has a feedback signal.

According to the signal, the stepper motor driver takes corresponding action measures or signal feedback to the PLC, and the PLC determines the next program processing.

The stepper motor only needs to add an encoder to feed back to the PLC or controller, and it can achieve the same effect as a closed-loop stepper motor, forming a closed-loop control system.

Advantages of closed-loop stepper motors 1.

The subdivision driving mode of the stepper driver has two advantages: low-speed vibration is small, and the positioning accuracy is high.

For applications that require low-speed operation or positioning accuracy below 0.90 degrees, subdivided stepper motor drivers are widely used.

The basic principle is to precisely control the currents of the two coils of the motor according to the sine and cosine steps, so that the the distance of step angle can be divided into several subdivisions.

For example, the driving mode of 16 subdivisions can make a stepping motor with 200 standard steps per circle reach a high operating accuracy of 25,000 steps per circle.The subdivision driving method is an extremely effective method to reduce vibration, but there are the following points to note: The subdivision drive works better at low speed.

If the input frequency is too fast, for the subdivision waveform, since the desired current waveform cannot be obtained, the tracking accuracy of the stepper motor will deteriorate.

First determine the torque required for the stepper motor to drag the load.

Determine the operating speed of the stepper motor.The speed index is very important in the selection of a stepper motor.

The characteristic of a stepper motor is that as the motor speed increases, the torque decreases.

The speed of the decrease is related to many parameters, such as the drive voltage of the driver and the phase current of the stepping motor, motor phase inductance, motor size, etc.

The general rule is: the higher the drive voltage, the slower the torque drop; the greater the motor's phase current, the slower the torque drop.3.

According to the two important indicators of the maximum load torque and speed, and then refer to the torque-frequency characteristics, you can choose a stepping motor that suits you.4.

Motor is damp: Insulation reduction due to water ingress or dampness is a common cause of damage.

Daily protection should be done.

Pay attention to insulation and test regularly.

Overload: If the protection function is normal (appropriate thermal relay is installed), it will generally not happen.

However, it should be noted that because the thermal relay cannot be calibrated, and the protection value is not very accurate, the selection is not appropriate, etc., and the manual setting is automatically reset, so when protection is needed, it often does not work, or it may After several protections, the real reason was not found, and the protection value was artificially increased.

The internal reasons of the motor: due to the damage of the bearing, it is also the main reason that the end cover is worn, the main shaft is worn, the rotor is bored, and the wire package is damaged.

Some power outputs are equal power output, and some are equal torque output (approximate only).

Stepper motors belong to the category of equal torque output, but the power also has a maximum limit, so the torque is basically the same at low speed, but after reaching a certain speed, it is known to be reduced.

If the power output is equal, then the speed and torque are directly inversely proportional.

As the speed increases, the back electromotive force becomes larger.

The stepping motor uses pulse current when the motor step rotates, the inductance of each phase winding of the motor will form a back electromotive force; the higher the frequency, the greater the back electromotive force.

Under its action, the phase current of the step motor decreases with the increase of frequency (or speed), resulting in a decrease in torque.