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SECTION 5: TORQUE VERSUS SPEED
CHARACTERISTICS
5.1 MOTOR PERFORMANCE
All stepper motors exhibit instability at their natural frequency and harmonics
of that frequency. Typically, this instability will occur at speeds between 50
and 1000 full steps per second and, depending on the dynamic motor load
parameters, can cause excessive velocity modulation or improper position-
ing. This type of instability is represented by the open area at the low end
of each Torque vs. Speed curve.
There are also other instabilities which may cause a loss of torque at step-
ping rates outside the range of natural resonance frequencies. One such
instability is broadly defined as mid-range instability. Usually, the damping
of the system and acceleration/deceleration through the resonance areas
aid in reducing instability to a level that provides smooth shaft velocity and
accurate positioning. If instability does cause unacceptable performance
under actual operating conditions, the following techniques can be used to
reduce velocity modulation.
1)
Avoid constant speed operation at the motor's unstable frequencies.
Select a base speed that is above the motor's resonant frequencies
and adjust acceleration and deceleration to move the motor through
unstable regions quickly.
2)
The motor winding current can be reduced as described in Section
4.5. Lowering the current will reduce torque proportionally. The re-
duced energy delivered to the motor can decrease velocity modulati-
on.
3)
Using another step resolution may provide smoother operation and
reduce the effects of mid range instability. Note that microstepping
changes the shaft speed for a given pulse input rate.
Summary of Contents for SLO-SYN SS2000MD4-M
Page 1: ...INSTALLATION INSTRUCTIONS for SLO SYN MODEL SS2000MD4 M MICROSTEP TRANSLATOR DRIVE...
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