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 __________.
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?
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.)
RCP ammeter indications
During a reactor coolant pump (RCP) locked rotor event, RCP motor current will…
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?
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?
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?
Excessive duration of peak starting current with zero system flow rate.
When a 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?
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?
Motor windings will begin to heat up
A thermal overload device for a large motor protects the motor from…
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?
Thermal overload device
Which one of the following will result from prolonged operation of an AC induction motor with
excessively high stator temperatures?
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…
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…
gradual motor bearing damage.
Which one of the following trip signals will trip the breaker for an operating motor that experiences a
seized rotor?
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?
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 __________.
increase; remain the same
Excessive current will be drawn by an AC induction motor that is operating…
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 __________.
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.)
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.)
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 __________.
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
__________.
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?
Negative MVAR (VARs in) with a leading power factor
A diesel generator (DG) is supplying both KW and KVAR to an electrical bus that is connected to an
infinite power grid. Assuming DG and bus voltage do not change, if the DG voltage regulator
setpoint is increased slightly, DG KW will __________; and DG amps will __________.
remain the same; increase
A diesel generator (DG) is supplying an electrical bus that is connected to an infinite power grid.
Assuming DG terminal voltage and bus frequency do not change, if the DG governor setpoint is
increased from 60.0 Hz to 60.1 Hz, DG KVAR load will __________; and DG amps will __________.
remain the same; increase
A main generator that is connected to an infinite power grid has the following indications:
600 MW
100 MVAR (out)
13,800 amps
25 KV
If main generator field current is decreased, amps will initially __________; and MVAR will initially
__________.
decrease; decrease
A diesel generator (DG) is supplying both KW and KVAR to an electrical bus that is connected to an
infinite power grid. Assuming bus voltage does not change, if the DG voltage regulator setpoint is
decreased slightly, DG KW will __________; and DG amps will __________.
remain the same; decrease
A main generator that is connected to an infinite power grid has the following indications:
100 MW
0 MVAR
2,900 amps
20 KV
If main generator excitation is increased, amps will __________; and MW will __________.
increase; remain the same
A main generator is supplying power to an infinite power grid. If the generator field current is slowly
and continuously increased, the generator will experience high current due to: (Assume no generator
protective actuations occur.)
. excessive generator MVAR out.
Two identical 1,000 MW generators are operating in parallel supplying the same isolated electrical
bus. The generator output breakers provide identical protection for the generators. Generator A and
B output indications are as follows:
Generator A Generator B
22 KV 22 KV
60.2 Hertz 60.2 Hertz
800 MW 800 MW
50 MVAR (out) 25 MVAR (in)
A malfunction causes the voltage regulator for generator B to slowly and continuously increase the
terminal voltage for generator B. If no operator action is taken, generator B output current will…
initially decrease, and then increase until the output breaker for generator B trips on overcurrent.
Refer to the partial drawing of two identical radial-flow centrifugal pumps in a cooling water system
(see figure below). Each pump is driven by an identical three-phase AC induction motor.
The cooling water system is being returned to service following maintenance on the pumps. Pump A
was started five minutes ago to initiate flow in the cooling water system. Pump B is about to be
started.
When pump B is started, which one of the following would cause the motor ammeter for pump B to
remain off-scale high for a longer time than usual before stabilizing at a lower running current?
Pump B was initially rotating in the reverse direction
A main turbine-generator is operating in parallel with an infinite power grid. If the turbine control
valves (or throttle valves) slowly fail open, the generator will experience high current primarily due
to… (Assume no generator protective actuations occur.)
excessive generator MW.
A main generator is operating and connected to an infinite power grid. Elevated main generator
winding temperature requires a reduction in reactive load from 200 MVAR (out) to 150 MVAR (out).
To accomplish the reactive load reduction, the operator must __________ the generator field current;
when generator reactive load equals 150 MVAR (out) the generator power factor will be __________
than the initial power factor.
decrease; larger
A main generator that is connected to an infinite power grid has the following indications:
22 KV
60 Hertz
575 MW
100 MVAR (in)
Which one of the following contains a combination of manual adjustments to the main generator
voltage regulator and speed control setpoints such that each adjustment will initially result in an
increase in main generator amps?
Voltage Speed
Setpoint Setpoint
Decrease Increase
A nuclear power plant startup is in progress. The main generator has just been connected to the
power grid with the following generator indications:
20 KV
288 amps
10 MW
0 MVAR
The operator suspects the main generator is operating under reverse power conditions and attempts to
increase generator load (MW) normally. If the main generator is operating under reverse power
conditions when the operator attempts to increase generator load, generator MW will initially
__________; and generator amps will initially __________.
decrease; decrease
A main generator is connected to an infinite power grid with the following generator output
parameters:
22 KV
60 Hertz
575 MW
100 MVAR (in)
Which one of the following contains a combination of manual adjustments to the main generator
voltage regulator and speed control setpoints such that each adjustment will initially result in a
decrease in main generator amps?
Voltage Speed
Setpoint Setpoint
Increase Decrease
A main generator is connected to an infinite power grid with the following initial generator
parameters:
22 KV
60 Hertz
600 MW
100 MVAR (out)
Which one of the following contains a combination of manual adjustments to the main generator
voltage regulator and speed control setpoints such that each adjustment will initially result in an
increase in main generator amps?
Voltage Speed
Setpoint Setpoint
Increase Increase
A main generator is connected to an infinite power grid. Which one of the following pairs of main
generator output parameters places the generator in the closest proximity to slipping a pole?
800 MW; 600 MVAR (in)
A main generator is connected to an infinite power grid with the following initial generator
parameters:
22 KV
60 Hertz
600 MW
100 MVAR (out)
Which one of the following contains a combination of manual adjustments to the main generator
voltage regulator and speed control setpoints such that each adjustment will initially result in a
decrease in main generator amps?
Voltage Speed
Setpoint Setpoint
Decrease Decrease
During a surveillance test, a 4,000 KW diesel generator (DG) and a 1,000 MW main generator (MG) at
a nuclear power plant are connected to the same power grid.
The following stable generator output conditions exist:
Diesel Generator Main Generator
700 KW 800 MW
200 KVAR (out) 100 MVAR (out)
A malfunction then occurs, causing the voltage regulator for the MG to slowly and continuously
increase the MG field current. If no operator action is taken, the DG output current will __________
until a breaker trip separates the generators.
initially decrease, and then increase
A main generator is connected to an infinite power grid with the following generator output
parameters:
22 KV
60 Hertz
575 MW
100 MVAR (in)
Which one of the following contains a combination of minor adjustments to the main generator
voltage regulator and speed control setpoints such that each adjustment will cause the main generator
to operate at a power factor closer to 1.0? (Assume the generator power factor remains less than 1.0.)
Voltage Speed
Setpoint Setpoint
Increase Increase
A main turbine-generator is connected to an infinite power grid with the following generator output
parameters:
25 KV
20,000 amps
830 MW
248 MVAR (out)
Which one of the following will significantly increase main generator output amperage without a
significant change in main generator MW output? (Assume the generator power factor remains less
than 1.0.)
Increasing the main generator voltage regulator setpoint
