Motor Starting Methods Summary

Method	Advantages	Disadvantages
Across-the -Line	Simple, Cost-Effective	High Current Inrush High Starting Torque Abrupt Start
Reduced-voltage autotransformer	High output torque vs. starting current. Some Flexibility in starting characteristics due adjustable taps on autotransformers	Limited duty cycle Large equipment size due to autotransformers
Reduced-Voltage Resistor or Reactor	High output torque vs. starting current	Limited duty cycle Limited flexibility in starting characteristics Higher inrush current than with reduced-voltage autotransformer Large equipment size due to resistors/reactors
Wye-Delta	Relatively low inrush current Relatively simple starter construction Good for long acceleration times	Relatively low output torque vs. starting current Limited flexibility in starting characteristics Requires special motor construction
Part-Winding	Relatively Simple starter construction	Relatively low output torque vs. starting current Not suitable for frequent starts Requires special motor construction
Solid-state soft starter	Smooth Acceleration Low inrush current High flexibility in starting characteristics Typically offers deceleration control also Typically integrates with industrial automation infrastructure	Relatively Expensive Sensitive to power quality Heat dissipation and ambient temperature are a concern
Rotor Resistance	Smooth acceleration available Good flexibility in starting characteristics Can be used for speed control also	Complicated controller design Requires expensive wound-rotor motor construction
Adjustable Speed Drive	Smooth Acceleration Low inrush current High flexibility in starting characteristics Offers deceleration and speed control also Typically integrates with industrial automation infrastructure	Cost-prohibitive unless speed control is required also Sensitive to power quality Heat dissipation and ambient temperature are a concern Continuous harmonic currents can create power quality issues

Source: Electrical Engineering Portal