The correct answer is: C. open-circuit in the winding
A single-phase induction motor runs slower than normal when there is an open-circuit in the winding. This is because the winding is what provides the magnetic field that causes the motor to rotate. When there is an open-circuit, the magnetic field is not as strong, and the motor does not rotate as fast.
Worn bearings can also cause a single-phase induction motor to run slower than normal. However, this is not as likely as an open-circuit in the winding. Worn bearings can cause the motor to vibrate, which can make it run slower.
A short-circuit in the winding can also cause a single-phase induction motor to run slower than normal. However, this is not as likely as an open-circuit in the winding. A short-circuit in the winding can cause the motor to overheat, which can make it run slower.
Therefore, the most likely defect that would cause a single-phase induction motor to run slower than normal is an open-circuit in the winding.
Here is a more detailed explanation of each option:
- A. Worn bearings
Worn bearings can cause a single-phase induction motor to run slower than normal. This is because the worn bearings can cause the motor to vibrate, which can make it run slower. However, this is not as likely as an open-circuit in the winding.
- B. Short-circuit in the winding
A short-circuit in the winding can also cause a single-phase induction motor to run slower than normal. This is because a short-circuit in the winding can cause the motor to overheat, which can make it run slower. However, this is not as likely as an open-circuit in the winding.
- C. Open-circuit in the winding
The most likely defect that would cause a single-phase induction motor to run slower than normal is an open-circuit in the winding. This is because the winding is what provides the magnetic field that causes the motor to rotate. When there is an open-circuit, the magnetic field is not as strong, and the motor does not rotate as fast.
- D. None of the above
None of the above options are as likely as an open-circuit in the winding to cause a single-phase induction motor to run slower than normal.