Question 193Electricity/Electronics - QMED70% to pass
You are attempting to parallel two AC generators and the synchroscope pointer stops at a position other than 0°. What would happen if you close the circuit breaker at this position?
AI Explanation
The correct answer is B) a hazardous condition will be created by the cross current between the machines.
When synchronizing two AC generators, it is critical that their voltages, frequencies, and phase angles match exactly before closing the circuit breaker. If the synchroscope pointer stops at a position other than 0°, it indicates a phase difference between the generators. Closing the circuit breaker in this condition will result in a large cross-current flowing between the generators, creating a hazardous condition that could potentially damage the equipment.
The other answer choices are incorrect because: A) the incoming machine will not accept all the load, as the phase mismatch will cause uncontrolled load sharing; C) the frequency mismatch is not the primary issue, as the phase angle difference is the main concern; and D) the incoming machine will not trip out on low voltage release, but rather experience the dangerous cross-current condition.
Related Questions
#191 If the excitation of an alternator operating in parallel is decreased below normal and the other above normal, what will be the result on the alternator with the excitation decreased below normal? #192 When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. What does this mean? #194 After closing the circuit breaker to place two alternators with identical ratings in parallel, in terms of achieving a balance between the two alternators, what is the NEXT step? #195 What device is used so that the kilowatt load sharing can be adjusted on paralleled generators? #196 As shown in figure "1" of the illustration, a correctly connected synchronous transmission causes the receiver to be in correspondence with the transmitter. If the receiver is out of correspondence, 180 degrees out of zero, but the torque direction is correct as shown in figure "2", what figure shows the incorrect connections responsible for this condition? Illustration EL-0150