A Cutler-Hammer solid-state starter, now an Eaton product, is an electronic motor control device that provides smooth, reduced-voltage starting and stopping for three-phase motors. These starters use semiconductors to control the motor's acceleration and deceleration, offering adjustable settings for factors like initial torque and ramp time, which reduces electrical surges, extends motor lifespan, and minimizes mechanical stress compared to traditional motor starters. 
Key Features and Functions

• Reduced Voltage Control:
  Solid-state starters manage the voltage supplied to the motor, controlling the rate at which the motor accelerates. 
• Smooth Starting:
  By gradually increasing voltage, they prevent sudden electrical surges and mechanical shocks, which is beneficial for equipment longevity and system stability. 
• Adjustable Parameters:
  Users can typically adjust parameters such as:
  • Ramp-Up Time: The duration over which the voltage is ramped from a low value to full voltage. 
  • Initial Torque: A "kick start" function can provide an initial torque boost to overcome high-inertia loads. 
  • Ramp-Down Time: For controlled deceleration and soft stopping. 
• Bypass Contactor:
  Many units include an internal bypass contactor that closes after the ramp-up is complete, allowing the motor to run at full voltage and reducing heat buildup within the starter. 
• Protection and Fault Monitoring:
  Solid-state starters offer protection features and display fault information, allowing for quick identification and resolution of issues. 

How it Works (Simplified) 

1. 1. Start Command:
   When a start command is received, the starter's control circuitry begins to power the motor.
2. 2. Voltage Ramp:
   Instead of applying full line voltage immediately, the solid-state components (like SCRs) control the voltage supplied to the motor, ramping it up over a programmed period.
3. 3. Bypass:
   Once the voltage reaches its full value and the motor is running smoothly, an internal bypass contactor closes.
4. 4. Full Voltage Operation:
   The bypass contactor takes over the motor power, and the SCRs are turned off, allowing the motor to run at full across-the-line voltage.
5. 5. Stopping:
   For a soft stop, the sequence is reversed: the bypass contactor opens, and the SCRs are used to control the deceleration process before shutting the motor off.

Benefits

• Extended Equipment Life: Reduces mechanical stress and wear on the motor and connected machinery. 
• Reduced Electrical Surges: Minimizes peak current during startup, which lessens the strain on the electrical supply system. 
• Increased Control: Provides precise control over motor starting and stopping profiles, which is crucial for various applications, including pumps.