Motors and Generators Flashcards
If a reactor coolant pump (RCP) rotor seizes, RCP motor current will __________; and if the rotor
shears, RCP motor speed will __________.
A. increase, increase
B. increase, decrease
C. decrease, increase
D. decrease, decrease
increase, increase
A nuclear power plant is operating at steady-state 80 percent power when a reactor coolant pump
(RCP) shaft seizes. Which one of the following indications would not accompany the seized shaft?
A. Reactor coolant system pressure transient.
B. Decreased flow rate in the associated reactor coolant loop.
C. Decreased flow rate in the remaining reactor coolant loop(s).
D. Increased current to the affected RCP with possible breaker trip.
Decreased flow rate in the remaining reactor coolant loop(s).
A nuclear power plant is operating at steady-state 100 percent power when a reactor coolant pump
(RCP) malfunction occurs. Thirty seconds after the malfunction, which one of the following can be
used by an operator to determine whether the malfunction is a locked RCP rotor or a sheared RCP
rotor? (Assume no operator action is taken.)
A. Reactor trip status
B. Loop flow indications
C. RCP ammeter indications
D. Loop differential temperature indications
RCP ammeter indications
During a reactor coolant pump (RCP) locked rotor event, RCP motor current will…
A. increase due to the increased rotor torque.
B. increase due to the increased counter electromotive force (CEMF) in the stator.
C. decrease due to the decreased pump flow rate.
D. decrease due to the increased CEMF in the rotor.
increase due to the increased rotor torque.
A motor-driven cooling water pump is operating normally. How will pump motor current respond if
the pump experiences a locked rotor?
A. Decreases immediately to zero due to breaker trip.
B. Decreases immediately to no-load motor amps.
C. Increases immediately to many times running current, then decreases to no-load motor amps.
D. Increases immediately to many times running current, then decreases to zero upon breaker trip.
Increases immediately to many times running current, then decreases to zero upon breaker trip.
A cooling water pump is being driven by an AC induction motor. Which one of the following
describes how and why pump motor current will change if the pump shaft seizes?
A. Decreases due to decreased pump flow rate.
B. Decreases due to increased counter electromotive force.
C. Increases due to decreased pump flow rate.
D. Increases due to decreased counter electromotive force.
Increases due to decreased counter electromotive force.
A motor-driven centrifugal pump exhibits indications of pump failure while being started in an idle
cooling water system. Assuming the pump motor breaker does not trip, which one of the following
pairs of indications would be observed if the failure is a locked pump shaft?
A. Lower than normal running current with zero system flow rate.
B. Lower than normal running current with a fraction of normal system flow rate.
C. Excessive duration of peak starting current with zero system flow rate.
D. Excessive duration of peak starting current with a fraction of normal system flow rate.
Excessive duration of peak starting current with zero system flow rate.
When an AC motor-driven centrifugal pump was started, the motor ammeter reading immediately
increased to, and stabilized at, many times the normal operating value. Which one of the following
describes a possible cause for the ammeter response?
A. The pump was started with a fully closed discharge valve.
B. The pump was started with a fully open discharge valve.
C. The pump shaft seized upon start and did not rotate.
D. The pump shaft separated from the motor shaft upon start.
The pump shaft seized upon start and did not rotate.
If the generator bearings on a motor-generator set begin to overheat from excessive friction, which one
of the following will occur?
A. Generator current will begin to increase.
B. Generator windings will begin to heat up.
C. Motor current will begin to decrease.
D. Motor windings will begin to heat up.
Motor windings will begin to heat up.
A thermal overload device for a large motor protects the motor from…
A. sustained overcurrent by opening the motor breaker or motor line contacts.
B. sustained overcurrent by opening contacts in the motor windings.
C. instantaneous overcurrent by opening the motor breaker or motor line contacts.
D. instantaneous overcurrent by opening contacts in the motor windings.
sustained overcurrent by opening the motor breaker or motor line contacts.
Which one of the following will provide the initial motor protection against electrical damage caused
by gradual bearing failure?
A. Thermal overload device
B. Overcurrent trip relay
C. Underfrequency relay
D. Undervoltage device
Thermal overload device
Which one of the following will result from prolonged operation of an AC induction motor with
excessively high stator temperatures?
A. Decreased electrical current demand due to reduced counter electromotive force.
B. Increased electrical current demand due to reduced counter electromotive force.
C. Decreased electrical resistance to ground due to breakdown of winding insulation.
D. Increased electrical resistance to ground due to breakdown of winding insulation.
Decreased electrical resistance to ground due to breakdown of winding insulation.
Continuous operation of a motor at rated load with a loss of required cooling to the motor windings
will eventually result in…
A. cavitation of the pumped fluid.
B. failure of the motor overcurrent protection devices.
C. breakdown of the motor insulation and electrical grounds.
D. phase current imbalance in the motor and overspeed trip actuation
breakdown of the motor insulation and electrical grounds.
Thermal overload devices will provide the first electrical protection for a pump motor in the
event of…
A. a locked rotor upon starting.
B. an electrical short circuit.
C. gradual motor bearing damage.
D. a sheared shaft during operation.
gradual motor bearing damage.
Which one of the following trip signals will trip the breaker for an operating motor that experiences a
seized rotor?
A. Undervoltage
B. Underfrequency
C. Time-delayed overcurrent
D. Instantaneous overcurrent
Time-delayed overcurrent
A large AC motor has a maximum ambient temperature rating of 40°C. Which one of the following
will occur if the motor is continuously operated at rated load with an ambient temperature of 50°C?
A. Accelerated embrittlement of the motor windings, leading to an open circuit within the motor
windings.
B. Accelerated embrittlement of the motor windings, leading to a short circuit within the motor
windings.
C. Accelerated breakdown of the motor winding insulation, leading to an open circuit within the
motor windings.
D. Accelerated breakdown of the motor winding insulation, leading to a short circuit within the motor
windings.
Accelerated breakdown of the motor winding insulation, leading to a short circuit within the motor
windings.
A main generator that is connected to an infinite power grid has the following initial indications:
100 MW
0 MVAR
2,900 amps
20 KV
If main generator field current is reduced slightly, amps will __________; and MW will __________.
A. increase; decrease
B. decrease; decrease
C. increase; remain the same
D. decrease; remain the same
increase; remain the same
Excessive current will be drawn by an AC induction motor that is operating…
A. completely unloaded.
B. at full load.
C. with open-circuited stator windings.
D. with short-circuited stator windings
with short-circuited stator windings
A main generator that is connected to an infinite power grid has the following indications:
500 MW
300 MVAR (out)
2,800 amps
If main generator field current is reduced slightly, amps will __________; and MW will __________.
A. increase; decrease
B. increase; remain the same
C. decrease; decrease
D. decrease; remain the same
decrease; remain the same
A main generator is connected to an infinite power grid. If the voltage supplied to the generator field
is slowly and continuously decreased, the generator will experience high current due to… (Assume no
generator protective actuations occur.)
A. excessive generator MW.
B. excessive generator MVAR out.
C. excessive generator MVAR in.
D. generator reverse power.
excessive generator MVAR in.
An AC generator is supplying an isolated electrical system with a power factor of 1.0. If generator
voltage is held constant while real load (KW) increases, the current supplied by the generator will
increase in direct proportion to the __________ of the change in real load. (Assume the generator
power factor remains constant at 1.0.)
A. cube
B. square
C. amount
D. square root
amount
A main generator that is connected to an infinite power grid has the following indications:
600 MW
100 MVAR (in)
13,800 amps
25 KV
If main generator excitation current is increased slightly, amps will initially __________; and MW
will initially __________.
A. decrease; increase
B. increase; increase
C. decrease; remain the same
D. increase; remain the same
decrease; remain the same
A main generator that is connected to an infinite power grid has the following indications:
600 MW
100 MVAR (in)
13,800 amps
25 KV
If main generator excitation current is decreased slightly, amps will __________; and MVAR will
__________.
A. decrease; increase
B. increase; increase
C. decrease; decrease
D. increase; decrease
increase; increase
A main generator is connected to an infinite power grid. Which one of the following conditions will
exist if the generator is operating underexcited?
A. Negative MVAR (VARs in) with a leading power factor
B. Positive MVAR (VARs out) with a leading power factor
C. Positive MVAR (VARs out) with a lagging power factor
D. Negative MVAR (VARs in) with a lagging power factor
Negative MVAR (VARs in) with a leading power factor