Figure 5.44: Simple Stepper Motor Driver
When the pulse rate is flat, the current does not have time to reach the
desired value before it is turned off and the total torque generated is
only a fraction of the nominal one (
Figure 5.46).
How fast the current reaches its nominal value depends on three factor:
the winding's inductance, resistance and the voltage applied to it.
The inductance cannot be reduced. But the voltage can be temporarily
increased to bring the current to its desired level faster. The most
widely used technique is a high voltage chopper.
Current
Figure 5.45: Current Build-up in Phase
When the pulse rate is fast, the current does not have time to reach the
desired value before it is turned off and the total torque generated is
only a fraction of the nominal one (
Figure 5.46).
How fast the current reaches its nominal value depends on three factors:
the winding's inductance, resistance and the voltage applied to it.
The inductance cannot be reduced. But the voltage can be temporarily
increased to bring the current to its desired level faster. The most
widely used technique is a high voltage chopper.
Phase ON
nominal current
Figure 5.46: Effect of a Short ON Time on Current
5-34 Section 5 – Motion Control Tutorial
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