As shown in the illustrated reduced voltage...

As shown in the illustrated reduced voltage three phase squirrel cage induction motor controller, what is the functional purpose of the "S2" contactor? See illustration EL-0116.

No comments yet

Be the first to share your thoughts!

🔍 Key Concepts

• Trace how the S2 contactor is wired in both the power circuit (top diagram) and the control circuit (bottom diagram). Notice what it does to the resistors R and the main contactor M. • Think about the difference between a reduced-voltage starting period and the run period for this motor. When should the resistors be in the circuit, and when should they be bypassed? • Look at the answer choices mentioning wye–delta connections. Compare those to the actual motor connection shown in the illustration and decide if this controller is a wye–delta starter or a primary-resistor type starter.

💭 Think About

• Follow the current path from L1, L2, and L3 to the motor during starting: which contactors must be closed first, and what role does S2 play relative to the resistors? • After the timer (CR/TC) operates and the motor comes up to speed, which contactors need to change state so the motor reaches full-voltage run? How does S2 contribute to that transition? • If M is the main contactor and R is the resistor (or start) contactor, what would happen electrically if M and R or different motor configurations were energized at the same time without proper interlocking?

✅ Before You Answer

• Verify whether the motor in the illustration is actually shown with wye–delta leads, or if it is a single delta connection with series resistors in the line. • Confirm whether S2’s contacts are in series with the line or in parallel (bypassing) the resistors; this tells you if S2 is involved in allowing or preventing simultaneous operation. • Check if there are any auxiliary contacts or interlocks from S2 in the control circuit that would stop another contactor from energizing at the same time. This will directly relate to choices that mention "allows" vs "prevents" simultaneous operation.

🔍 Key Concepts

💭 Think About

✅ Before You Answer