Does the stepper motor have less torque in half step operation than in full step operation?
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Full step operation
The stepper motor has the highest torque during full step operation. However, in full step operation a stepper motor also has the most marked resonance points - that, in turn, have a negative impact on the torque. If, however, the operating speed lie near such a resonance frequency, it may be more advantageous to switch to microstep operation because the full torque of the motor cannot be used anyway at this frequency.
Half step operation
As can be seen in the animation of the operation of a stepper motor in half step, 2 windings (phases) are alternately energized,1 winding (phase), 2 windings (phase). The vectorial sum or geometrical addition of the two phase currents I (motor = √ Ia2 + Ib2) give the half step torque of 70.7% in respect to full step operation. The new SMCI 32 and SMCI 47 microstep drives have an automatically built-in current compensation. During the half step phase the current in the phase that is presently active is increased by a factor of 1.4 (which is thermally allowed because the other phase is presently off) and, due to this current increase, we can reach nearly 95% torque of the full step operation in half step operation.
Quarter step operation and smaller
Similar to half step operation, the vectorial phase current in quarter step is even smaller and the
resulting torque is approximately 55% and in 1/8 step at 45% compared to full step
operation.
Automatic current increases are integrated in the stepper motor operation of the Nanotec SCMI series and in all new Plug & Drive stepper motors, in both half step operation and in smaller microstep operations which means, therefore, that approximately the same (95%) torque is reached as in full step operation.
All torque characteristics were recorded in 1/4 step mode with current compensation.
A further advantage: Less energy is generally required in microstep. The reason for this is also the lower residual ripple that is largely avoided due to better concentricity resonances.
