The two factors used to determine the speed of ac motors are the frequency of the power supply and the number of poles in the motor winding.
Explanation:
The frequency of the power supply and the number of poles of the machine states the synchronous speed.
The poles combined with ac line frequency determines the no-load revolutions per minute of the monitor. So all four-pole motors will run at same speed under no-load conditions, then all six-pole motors will run at the same speed.
The speed of the induction motor depends on stator frequency "s ". By varying the stator voltage and constant supply frequency the speed can be controlled. The two main components of the electric motor are stator and rotor.
The all purpose one will work or you could use type C I believe.
I think the answer is the third option
Answer:
B A and C
Explanation:
Given:
Specimen σ
σ
A +450 -150
B +300 -300
C +500 -200
Solution:
Compute the mean stress
σ
= (σ + σ)/2
σ
= (450 + (-150)) / 2
= (450 - 150) / 2
= 300/2
σ = 150 MPa
σ
= (300 + (-300))/2
= (300 - 300) / 2
= 0/2
σ = 0 MPa
σ
= (500 + (-200))/2
= (500 - 200) / 2
= 300/2
σ = 150 MPa
Compute stress amplitude:
σ
= (σ - σ)/2
σ
= (450 - (-150)) / 2
= (450 + 150) / 2
= 600/2
σ = 300 MPa
σ
= (300- (-300)) / 2
= (300 + 300) / 2
= 600/2
σ = 300 MPa
σ
= (500 - (-200))/2
= (500 + 200) / 2
= 700 / 2
σ = 350 MPa
From the above results it is concluded that the longest fatigue lifetime is of specimen B because it has the minimum mean stress.
Next, the specimen A has the fatigue lifetime which is shorter than B but longer than specimen C.
In the last comes specimen C which has the shortest fatigue lifetime because it has the higher mean stress and highest stress amplitude.
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