10 factors that should be considered when you choose a stepper motor

Stepper motors are widely used in many fields, so what factors should users pay attention to when facing a variety of stepper motors? This blog provides you with the following reference factors. Hope it can help you avoid troubles caused by improper selection.

1. Torque of the stepper motor

The holding torque of a stepper motor is similar to what is called "power" by a conventional motor. Of course, there are essential differences. The physical structure of the stepping motor is completely different from AC and DC motors, and the output power of the motor is variable.

We usually choose the model of the motor according to the required torque (that is, the torque of the object to be driven).

Generally speaking, if the torque is below 0.8N.m, we will choose 20, 28, 35, 39, 42 (the diameter or squareness of the motor body, unit: mm); if the torque is around 1N.m, it is best to choose 57 The motor is more suitable. When the torque is a few N.m or greater, you have to choose a stepper motor with specifications such as 86, 110, and 130.

2. The speed of the stepper motor

Special consideration should also be given to the speed of the motor. Because the output torque of the motor is inversely proportional to the speed. That is to say, the output torque of the stepper motor is large at low speed (hundreds of revolutions per minute or lower), and its output torque is very small at high speed rotation (1000 revolutions per minute - 9000 revolutions).

Of course, some working conditions require high-speed motors, and it is necessary to measure the coil resistance, inductance and other indicators of the stepping motor. Generally, it is best to choose a motor with a small inductance and a large phase current. As a high-speed motor, a large output torque can be obtained. On the contrary, in the case of requiring low speed and high torque, it is better to choose an inductance of more than ten or tens of mH, and a larger resistance.

3. The no-load starting frequency of the stepper motor

The no-load starting frequency of a stepper motor is usually called "no-load starting frequency", which is an important indicator for choosing a motor. If the motor is required to start and stop frequently in an instant, and the speed is around 1000 rpm (or higher), usually "accelerated start" is required.

If you need the motor to start directly to achieve high speed, it is best to choose a reactive or permanent magnet motor. The "idling frequency" of these motors is relatively high.

4. The number of phases of the stepper motor

Motors with different phase numbers have different working effects. The more the number of phases, the smaller the step angle can be made, and the vibration during work is relatively small.

In most occasions, two-phase motors are used more. In the working environment of high speed and high torque, it is more practical to choose a three-phase stepping motor.

5. working environment

According to the working environment of the stepper motor, you can choose a special stepper motor that can be waterproof, oil-proof and shock-proof, etc. for some special occasions. For example, underwater robots need waterproof motors. For special-purpose motors, it is necessary to select motors with special functions.

6. Motor operating speed range

The speed range of stepper motors is generally used within 600RPM, and stepper motors have torque-frequency characteristics. The output torque of the motor running at 600RPM is about 40% of the rated torque of the motor (the user can improve the output torque of the motor at high speed by appropriately increasing the power supply voltage).

When selecting the output torque of the motor, a certain safety margin should be considered to avoid the occurrence of lost steps during the operation of the motor.

7. The installation size of the motor

The installation size of the motor is also an aspect that needs to be considered, including: the size of the motor's mounting flange, body size, output shaft size and output shaft type (optical shaft, platform shaft and keyed shaft).

8. Control accuracy

If you have higher precision requirements, stepper motors with encoders that are closed loop stepper motor are preferred.

9. Conventional drive mode of stepper motor

Conventional drive methods of stepper motors can be divided into constant voltage drive and constant current drive, unipolar drive and bipolar drive. Constant voltage drive refers to a constant drive voltage, which needs to be matched with a suitable resistance value, while constant current drive is usually aimed at motors with small resistance. The unipolar drive and bipolar drive are mainly due to the difference in the number of power tubes in the drive circuit, and the direction of the coil current in the coil is different.

10. Further communicate and confirm the model with the technical engineer of the manufacturer

If necessary, it is best to communicate further with the technical engineer of the manufacturer, so as to confirm whether the stepper motor you want to choose can meet all the indicators you require.

All in all, when purchasing a stepper motor, you need to consider the above factors. In addition to the above-mentioned aspects, it is recommended that you pay attention to whether the stepper motor has good waterproof, oil-proof and anti-corrosion performance. Only then can it be better applied to special occasions, and if you need to use a stepper motor with special specifications, it is recommended to discuss with the manufacturer about ordering.

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