When thick wire is used for winding of stepping motor, the coil resistance Rw is very small, as shown in the figure below. In each phase coil, the external resistance R is connected in series to limit the current flowing through the winding to be less than the rated current I. To limit the current flowing through the winding, two methods can be adopted: reducing the power supply voltage and connecting the external resistance R in series.
Only when the stepping motor operates at low speed, it does not need external resistance. The coil is directly driven by the power supply voltage and external power semiconductor for constant voltage. At this time, the winding wire radius of the stepping motor is smaller, the number of turns is more, and the resistance value is larger. This method is mostly used in small current drive mode.
When driving the stepper motor, use the external voltage, for example, as shown in the figure below. When the driving voltage is 24V, stop rotating after reaching the position, and switch its voltage to 5v, the total loss power will decrease. This is the two voltage control mode. You can also add a certain amount of current to maintain the positioning accuracy according to the type of load. Another method is to use low voltage drive at low speed, and switch to high voltage drive at high speed.