As shown in the illustrated solid-state stepless acceleration starting method graphs, which figure graphs a starting method that would require a tachometer input? See illustration EL-0143.
• Open-loop vs closed-loop control in solid-state motor starters • Difference between controlling current, voltage, and speed during acceleration • What a tachometer feedback signal is actually measuring in a motor control system
• Look at each graph and ask: which variable is being ramped and controlled during the start period? • Which type of control would need a direct measurement of shaft rotation to maintain the programmed ramp shape? • For current-limited or voltage-ramp starters, what internal quantities can the controller sense without any external mechanical sensor?
• Identify which figure uses motor speed vs time rather than current or voltage vs time • Recall that a tachometer provides a signal proportional to rotational speed, not current or voltage • Confirm that the chosen figure represents a closed-loop speed ramp, which cannot be done accurately without speed feedback
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