ElmoMC SimplIQ Software Manual - Manual (Page 138)

SimplIQ Software Manual Unit Modes
MAN-SIMSW (Ver. 1.4)
10-8
0 0.2 0.4 0.6 0.8 1
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Com m and generator
output
Com m and to the s peed
c ontroller
S top s witc h
ac tive
Figure 10-7: Results of Sample Stop Switch Activation
When the stop switch is applied, the speed command is brought to a complete stop,
decelerating at 100,000 counts/second
2 . When the switch is released, the acceleration of
100,000 counts/second 2 is used to recover the output of the reference generator.
10.3 Unit Mode 3: Stepper Mode
The stepper unit mode enables the motor to rotate without feedback control. The motor
field is rotated in the desired direction and the rotor magnet is assumed to follow. The
field should not be rotated too abruptly in order to enable the rotor to track its desired
direction. If the rotor misses a full electrical revolution, it will be attracted to a wrong
electrical equilibrium, with no feedback to correct it. Moreover, if the field rotation is
stopped abruptly, the motor will not brake properly. If the rotor misses half an electrical
revolution, it will begin accelerating — and the net braking torque sum for an electrical
revolution will be zero.
Specifying a higher motor current enables larger accelerations and decelerations, but also
causes a loss of more power in a steady state. In stepper mode, the stator field and rotor
magnet are nearly equal most of the time, and the motor efficiency is very low.
The SimplIQ drive uses stepper mode mainly for safe testing and controller tuning before
any feedback control is tuned. The SimplIQ drive can serve as an advanced micro-stepper
driver, with 1024 micro-steps per electrical revolution. The main limitation is that the
SimplIQ drive is a three-phase driver, while most stepper motors on the market are two-
phased.