What type of couplings are used in applications where variable speed operations occur?
A. Rigid
B. Fluid
C. Flexible
D. Rotating
A. Incorrect. Rigid couplings are used in applications where only small amounts of misalignment can be tolerated without damage to equipment or decreased performance.
B. Correct. Fluid couplings are used in applications where variable speed operations occur.
C. Incorrect. Flexible couplings are used most frequently in general mechanical power transmission service because they allow some misalignment without affecting the transmission of power.
D. Incorrect. Rotating is not a type of coupling.
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The motor is loaded by a unidirectional constant-torque load of 40 Nm. A countercurrent braking is performed on the motor. Calculate the following:
A 60 Hz, 480 V, three-phase, Y-connected induction machine has the following
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b. Motor current just after the voltage sequence is reversed
c. Current at the moment when the motor stops
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e. Motor current at the new steady-state point
f. Motor torque at the new steady-state point
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