#### Problem solving

Common problems with stepper motors (NiMotion closed-loop integrated stepper ...
Release Date : 2019-03-08 09:36:04

1. What is the accuracy of the stepper motor? Do you accumulate?

The accuracy of the stepper motor is 3-5% of the step angle and does not accumulate.

2. What is the allowable temperature of the stepper motor?

If the temperature of the stepping motor is too high, the magnetic material of the motor will be demagnetized first, which will cause the torque to drop and even lose the step. Therefore, the maximum temperature allowed by the motor surface should depend on the demagnetization point of the magnetic material of different motors;

Generally speaking, the demagnetization point of magnetic materials is above 130 degrees Celsius, and some even up to 200 degrees Celsius, so the external temperature of the stepper motor is completely normal at 80-90 degrees Celsius.

3. Why does the torque of the stepper motor decrease with the increase of the rotational speed?

When the stepper motor rotates, the inductance of each phase winding of the motor will form a back electromotive force; the higher the frequency, the larger the back electromotive force. Under its action, the motor decreases with increasing frequency (or speed), resulting in a drop in torque.

4. Why can the stepping motor run normally at low speed, but if it is higher than a certain speed, it can't start, accompanied by howling?

The stepping motor has a technical parameter: the no-load starting frequency, that is, the pulse frequency that the stepping motor can start normally under no-load conditions. If the pulse frequency is higher than this value, the motor cannot start normally, and lost or blocked may occur. However, NiMotion's closed-loop integrated stepper motor has solved the lost step problem. In the case of load, the starting frequency should be lower. If the motor is to be rotated at a high speed, the pulse frequency should have an acceleration process, that is, the starting frequency is low, and then rise to the desired high frequency according to a certain acceleration (the motor speed is increased from low speed to high speed, NiMotion's integrated stepping motor can Freely set acceleration and deceleration).

5. How to overcome the vibration and noise of the two-phase hybrid stepping motor at low speed? The large vibration and noise of the stepping motor at low speed is its inherent shortcoming. Generally, the following solutions can be used to overcome:

A. If the stepping motor works just in the resonance zone, the resonance zone can be avoided by changing the reduction ratio and other mechanical transmissions;
B. Using a driver with subdivision function, or directly using an integrated stepper motor, this is the most common and easiest method;
C. Change to a stepper motor with a smaller step angle, such as a three-phase or five-phase stepper motor;
D, replaced by AC servo motor, can almost completely overcome the vibration and noise, but the cost is higher;
E. A magnetic damper is added to the motor shaft. This product is available on the market, but the mechanical structure changes greatly.

6. Does the subdivision of the subdivision drive represent accuracy?

The subdivision technology of the stepping motor is essentially an electronic damping technology (please refer to the relevant literature). Its main purpose is to reduce or eliminate the low frequency vibration of the stepping motor, and improve the running accuracy of the motor is only a supplementary function of the subdivision technology. For example, for a two-phase hybrid stepping motor with a step angle of 1.8°, if the subdivision number of the subdivision driver is set to 4, then the operating resolution of the motor is 0.45° per pulse, and the accuracy of the motor can be reached or approached. 0.45° also depends on other factors such as the subdivision current control accuracy of the subdivision driver. The accuracy of subdivision drivers from different manufacturers may vary greatly; the larger the number of subdivisions, the more difficult it is to control. However, the integrated stepping motor of NiMotion in China can still achieve better accuracy than 0.2 degrees even under 16 or 32 subdivisions. It is an excellent enterprise in the industry for precision control.

7. What is the difference between the series connection method and the parallel connection method of the four-phase hybrid stepping motor and the driver?

The four-phase hybrid stepping motor is generally driven by a two-phase driver. Therefore, the four-phase motor can be connected to two phases by a series connection or a parallel connection method. The series connection method is generally used in the case where the motor speed is low. In this case, the required output current of the driver is 0.7 times of the motor phase current, so the motor generates less heat; and the connection method is generally used in the case where the motor speed is high (also called high speed connection). Method), the required driver output current is 1.4 times of the motor phase current, so the motor generates a large amount of heat.

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

A, the determination of the voltage

The power supply voltage of a hybrid stepper motor driver is generally a wide range (for example, the STM42/STM57/STM86 integrated motor has a power supply range of DC10V-48V), and the power supply voltage is usually selected according to the operating speed and response requirements of the motor. If the motor has a higher operating speed or a faster response, the voltage value is also high, but note that the ripple of the power supply voltage cannot exceed the maximum input voltage of the driver. Otherwise, the driver will be damaged under normal conditions. The NiMotion integrated stepper motor can be set. Overvoltage alarm voltage, alarm when the set value is exceeded.

B, the determination of the current

The power supply current is generally determined based on the output phase current I of the driver. If a linear power supply is used, the power supply current can generally take 1.1 to 1.3 times of I; if a switching power supply is used, the power supply current can generally take 1.5 to 2.0 times that of I.

9. Under what circumstances is the offline signal FREE of the hybrid stepper motor driver used?

When the offline signal FREE is low, the current output from the driver to the stepping motor is cut off, and the motor rotor is in a free state (offline state). In some automation equipment, if the motor drive shaft (manual mode) is required to be directly powered by the stepper drive, the FREE signal can be set low, the motor can be taken offline, and manually operated or adjusted. After manual completion, set the FREE signal high to continue automatic control.