What affects the safety of deceleration stepper motors, how to choose

Depending on the speed, the solution to increasing the torque of a brushless stepper motor is different. The solution is not only the brushless stepper motor, but also the drive circuit.

1. The method of increasing the torque of brushless stepping motor at low speed

1) Select a stepper motor with a small step angle. At low speeds, as the number of teeth on the rotor increases, the torque becomes greater. A stepper motor with a small step angle can achieve high torque. If the number of teeth of the HB rotor is 50 teeth, the flux leakage of the permanent magnet will increase, but the step size will be proportional. This conclusion is valid under 100 teeth. The three-phase HB type stepper motor is changed from 1.2 (rotor 50 teeth) to 0.6 (rotor 100 teeth). Approximately 1.4 to 1.8 times increase in low speed torque.

2) Bipolar wiring

3) Efficiency can be doubled. Two-phase unipolar or bipolar stepper motors are commercially available, but bipolar drives have more power transistors than unipolar ones.

2. The method of increasing the torque of brushless stepping motor at high speed

1) Reduce the number of turns and reduce L. In the standard product of the motor manufacturer, the inductor L is selected to be small, and the rated current becomes large.

2) The magnetic flux of the permanent magnet should be small. If the manufacturer cannot reduce the permanent magnet, it can increase the air gap, reduce the counter electromotive force at high speed, increase the current, increase the torque, and change the speed, and the torque characteristic changes from low speed to high speed. In a straight line, high-speed torque increases and so does the frequency of response.

3) Choose a motor with a step angle.

3. The method of improving the torque of the drive circuit when the brushless stepping motor is running at high speed

1) Increase the voltage of the driving current in order to maintain high speed and high speed, keep the current constant, and make the chopper in a constant current state. To keep the current constant, only the pulse frequency is increased. When the brushless stepper motor reaches a certain high speed, the voltage can only work in a constant voltage state. If the input voltage increases, it can still work at a constant current state at high speed. If the input voltage is increased, it can operate in a high-speed constant current state, thereby increasing high-speed torque.

2) When the drive circuit is off, the current in the current coil is reduced. When the power tube is turned off, the rate of change of current is large, and a very large induced voltage is generated in the coil. The power tube can be damaged and usually has a protective circuit function.