The synchronous speed of an AC motor is determined by the supply frequency and the number of poles in the machine. The formula for synchronous speed ($N_s$) is:
$N_s = \frac{120 \times f}{P}$
Where:
- $N_s$ = Synchronous speed in revolutions per minute (rpm)
- $f$ = Supply frequency in Hertz (Hz)
- $P$ = Number of poles
Synchronous Speed Calculation: Initial State
Given initial parameters:
- Frequency ($f_1$) = 50 Hz
- Number of poles ($P_1$) = 4
Calculate the initial synchronous speed ($N_{s1}$):
$N_{s1} = \frac{120 \times 50}{4} = \frac{6000}{4} = 1500 \text{ rpm}$
Synchronous Speed Calculation: Changed Parameters
The problem states that the frequency and pole number are halved. The load torque change does not affect the synchronous speed itself.
New parameters:
- New frequency ($f_2$) = $\frac{f_1}{2} = \frac{50}{2} = 25 \text{ Hz}$
- New number of poles ($P_2$) = $\frac{P_1}{2} = \frac{4}{2} = 2 \text{ poles}$
Calculate the new synchronous speed ($N_{s2}$):
$N_{s2} = \frac{120 \times f_2}{P_2} = \frac{120 \times 25}{2} = \frac{3000}{2} = 1500 \text{ rpm}$
Motor Speed Conclusion
After halving the frequency and the number of poles, the new synchronous speed of the motor remains 1500 rpm. For a synchronous motor, the operating speed is the synchronous speed.
Similar Questions
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A. A is non singular and the rows and columns of A are linearly independent
B. A is non-singular and the rows and columns of A are linearly dependent
C. A is non-singular and A has one zero rows
D. A is singular
E. A is singular and rows and columns of A are linearly dependent
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- Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : If $u = xy f\left(\frac{y}{x}\right)$, then $x \frac{\partial u}{\partial x} + y \frac{\partial u}{\partial y} = 2u$
Reason (R) : Given function u is homogeneous of degree 2 in $x$ and $y$.
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A. Partial fraction expansion
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C. Take Laplace transform of differential equation
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Choose the correct answer from the options given below : - A lag network for compensation normally consists of :
A. R, L and C elements
B. R and L elements
C. R and C elements
D. R only
E. L only
Choose the correct answer from the options given below :
Important Questions from Mixed Topic (CUET PG)
- Kalpsutra, the illustrated canonical text is from:-
- The Harappan city almost exclusively devoted to craft production was-:
- Mohandas Karamchand Gandhi launched quit India movement after the failure of:-
- The "Objectives Resolution" was introduced in constituent assembly by:-
- Who among the following was not a member of the constituent assembly:-
