Consider the table given :

Constructional feature	Machine type	Mitigation
P. Damper bars	S. Induction motor	X. Hunting
Q. Skewed rotor slots	T. Transformer	Y. Magnetic locking
R. Compensating winding	U. Synchronous machine	Z. Armature reaction
	V. DC machine

The correct combination that relates the constructional feature, machine type and mitigation is

The correct combination is P-U-X, Q-S-Y, R-V-Z.

Here is the step-by-step breakdown of how each constructional feature matches with its respective machine type and mitigation:

1. Damper Bars (P-U-X)
- Machine Type: Synchronous machine (U)
- Mitigation: Hunting (X)
- Explanation: In synchronous machines, hunting refers to the undesirable oscillations of the rotor about its equilibrium position, which can happen due to sudden load fluctuations. Damper bars are copper or aluminum rods embedded in the pole faces of the rotor. When hunting occurs, there is relative motion between the rotating magnetic field of the stator and the rotor. This relative motion induces current in the short-circuited damper bars, producing a damping torque that opposes the oscillations and brings the rotor back to synchronous speed.

2. Skewed Rotor Slots (Q-S-Y)
- Machine Type: Induction motor (S)
- Mitigation: Magnetic locking (Y)
- Explanation: In a squirrel-cage induction motor, magnetic locking (also known as cogging) occurs when the rotor teeth magnetically align and lock with the stator teeth due to strong magnetic attraction, making the motor fail to start. By skewing the rotor slots (positioning them at an angle relative to the shaft instead of parallel), the alignment between the stator and rotor teeth is offset along the length of the rotor. This prevents direct alignment, eliminates magnetic locking, and results in smoother torque.

3. Compensating Winding (R-V-Z)
- Machine Type: DC machine (V)
- Mitigation: Armature reaction (Z)
- Explanation: In a DC machine, the armature reaction causes distortion of the main field flux under the pole faces, which can lead to severe sparking at the brushes during heavy load changes. Compensating windings are auxiliary windings embedded in the main pole faces. They are connected in series with the armature winding but carry current in the opposite direction. This enables them to produce a magnetic field that directly cancels out the cross-magnetizing armature flux under the pole faces, thereby mitigating armature reaction effects.