What will be the impact of reduced voltage applied to a motor during the starting period?
• Ohm’s Law relationship between voltage and current in a motor circuit • How starting torque of an AC motor changes with applied voltage (often proportional to voltage squared) • How torque affects the motor’s acceleration time from standstill to running speed
• If you reduce the applied voltage, what normally happens to the current drawn by the motor at start, assuming the motor’s impedance doesn’t change drastically? • If the motor develops less torque at start, will it speed up faster or slower to reach full RPM? • How would a weaker “push” on the rotor (less torque) show up in terms of how long it takes the motor to get up to speed?
• Be clear whether lower voltage tends to increase or decrease starting current in a typical motor circuit. • Recall that starting torque ~ (applied voltage)^2 for many AC induction motors—how does that affect acceleration time? • Eliminate any choice where the change in current and the change in acceleration time do not logically match your understanding of torque vs voltage.
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