Wiring of the winding
Support » FAQ » Stepper motors
1. One half of the winding: Here only half of the windings of the motor are used, therefore the holding torque that can be achieved is also less than in the other modes. This mode only offers advantages in the high speed range of the 6-lead motors which is clearly apparent from the respective motor diagrams.
2. Parallel: The highest motor power is achieved in this mode. The low inductance keeps the torque of the motor constant, even at higher speeds, although a higher phase current is also required.
3. Serial: This mode is suited to the lower speed range where high torque is reached with low current. But due to the high inductance (double winding resistance, quadratic increase of the winding inductance), the torque drops off quickly at higher speeds.
The values specified in the datasheet always refer to one half of the winding. The following table shows the rule for converting the individual parameters to serial and parallel switching mode. This function can also be listed online on the overview page of the individual stepper motor series (under Type, Control).
| Value | 1 winding half as in datasheet | Serial | Parallel |
|---|---|---|---|
| Resistor | R | 2 * R | R/2 |
| Inductance | L | 4 * L | L |
| Phase current | I | I/√2 | I * √2 |
| Holding torque | M | M * √2 | M * √2 |
The holding torque is reached at the respective nominal current. If the current deviates, the value can be calculated from the proportionality between the phase current and holding torque. Half the current (in the same connection), therefore, leads to half the holding torque.
Note: This correlation only applies for the holding torque and for the lower speed range (where the torque has not yet dropped), but not for the entire motor curve. At high speeds, the set current can no longer reach its maximum value because the switching operations on the winding are then too fast. This (real) current reduction leads to a decrease in the motor curves with increasing speed. Because at one point, a lower current (I = U/2 * π * f * L ) is set due to the increasing frequency and, above all, due to the counter EMF that increases in proportion to the speed. (As soon as the counter EMF increases to the value of the supply voltage with increasing speed, the current approaches zero and thus no more torque can be generated.)
It is also possible to operate the motor briefly with higher current. Here, however, attention must be paid that the housing temperature does not exceed 80 °C (or up to 100 °C depending on the power-up time). Depending on the motor, saturation is reached at a multiple of 1, 2 to 5 times the value of the nominal current after which the torque no longer increases and only even more heat is produced which means the motor quickly overheats and the windings finally burn through.
