
246 Electric Motors and Drives
Half stepping
We have already seen how to step the motor in 30° incre-
ments by energizing the phases one at a time in the sequence
ABC A etc. Although this '1-phase-on' mode is the simplest
and most widely used, there are two other modes which are
also frequently used. These are referred to as the '2-phase-
on' mode and the 'half-stepping' mode. The 2-phase-on can
provide greater holding torque and a much better damped
single-step response than the
1-phase-on
mode; and the half
stepping mode permits the effective step angle to be halved -
thereby doubling the resolution - and produces a smoother
shaft rotation. ...