Discussion
A synchronous motor running at 1800 rpm is operated with the supply frequency of 60 Hz. Find the number of poles.
Answer: C
The motor has 4 poles. The synchronous speed of a motor depends on the supply frequency and the number of poles.
\[ N_s = \frac{120 f}{P} \]
\[ P = \frac{120 \times 60}{1800} = 4 \]
Eight poles would give 900 rpm, six poles 1200 rpm, and two poles 3600 rpm at 60 Hz, so only four poles gives 1800 rpm. The third option is the answer. As a check, 4 poles on a 60 Hz supply give 120 x 60 / 4 = 1800 rpm, which is the speed in the question.
No comment is present. Be the first to comment.
Loading…
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development