Question 245Electricity/Electronics - Assistant Engineer70% to pass
You are in the planning stages of setting the instantaneous trip of a ship's service generator circuit breaker. According to 46 CFR, Subchapter J (Electrical Engineering), what statement is true regarding the criteria for the instantaneous trip setpoint, assuming the generator is capable of being paralleled?
AI Explanation
The correct answer is D) The trip point should be set above but as close as practical to the maximum asymmetrical short circuit current available.
This is because 46 CFR Subchapter J, Section 111.12-1(a) states that the instantaneous trip setting of the ship's service generator circuit breaker should be set above, but as close as practical, to the maximum available asymmetrical short circuit current. This ensures that the breaker will trip quickly to clear a short circuit, but without setting the trip point so high that it could inadvertently trip during normal generator operation.
The other options are incorrect because A) setting the trip point exactly at the maximum short circuit current is too precise and could lead to unwanted tripping, B) setting it below the maximum is unsafe as it may not clear a short circuit quickly enough, and C) setting it considerably above the maximum could allow a short circuit to persist for too long before the breaker trips.
Related Questions
#243 Assuming that a ship's service generator is directly coupled to the prime mover, what condition must cause a prime mover to automatically shutdown? #244 In accordance with 46 CFR, Subchapter J (Electrical Engineering), each diesel engine driven generator prime mover must have an overspeed device, independent of the normal operating governor. If in testing the overspeed device, what should be the trip point setting in terms of rated speed? #246 There are very specific rules that govern the testing of generators found in the appropriate publication incorporated by reference. According to 46 CFR, Subchapter J (Electrical Engineering), which agency publishes the rules for the construction and testing of generators? #247 You are in the planning stages of setting the longtime overcurrent trip of a ship's service generator circuit breaker. According to 46 CFR, Subchapter J (Electrical Engineering), what statement is true regarding the criteria for the longtime overcurrent trip setpoint, assuming the generator is capable of being paralleled? #248 The turns ratio of the tapped step-down transformer shown in figure "C" of the illustration is four to one and all taps are equally spaced. If 440 volts were applied between 'H1' and 'H4', what would appear across 'X1' and 'X4'? Illustration EL-0082