Capacitor start and run 1-phase IM is basically a

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1-ph induction motor

Explanation: A capacitor start and run induction motor is a single-phase induction motor that utilizes two capacitors—one for starting and one for running—to improve torque characteristics and power factor. Despite using these capacitors to create a phase shift, it remains fundamentally a single-phase induction motor as it operates from a single-phase AC supply.

Working Principle: The stator contains two windings: a main winding and an auxiliary (starting) winding. A capacitor connected in series with the auxiliary winding causes the current in that winding to lead the current in the main winding, creating a rotating magnetic field necessary for starting. During running, a smaller permanent capacitor remains in the circuit to maintain higher efficiency and smoother torque, mimicking a two-phase system behavior while powered by a single-phase source.

Key Formulas: $T_{st} \propto I_m I_a \sin 	heta$; $	heta = 	an^{-1}(\frac{X_c}{R_a})$

Key Points: Uses a centrifugal switch to disconnect the start capacitor after reaching 75% speed.; The run capacitor remains permanently in the circuit to improve power factor and efficiency.; Provides high starting torque compared to resistance-split phase motors.; Operates quietly due to better balanced flux distribution.

Advantages: High starting torque; Improved power factor during operation; High efficiency; Smooth running with less vibration

Disadvantages: Expensive due to two capacitors and a centrifugal switch; Increased maintenance due to the centrifugal switch

Applications: Refrigerators; Compressors; Conveyors; Large capacity fans

Additional Info: The motor is often called a 'two-value capacitor motor'.. Option B is wrong because even though the auxiliary winding provides a 90-degree phase shift, the source remains single-phase.. Option D is wrong because a 3-phase motor requires a 3-phase supply and produces a balanced rotating magnetic field naturally.

Answer: A is correct — The capacitor start and run motor is a single-phase induction motor that uses capacitors to approximate a two-phase supply for improved starting and running performance.

Exam Tip: Always remember that in single-phase machines, 'phase' refers to the supply input, not the internal winding configurations or auxiliary circuits.

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