Flashcards in Study info Deck (85):
T or F After a DC test has been completed on a long cable, it is most important that the conductor under test be grounded for a sustained period of time.
T or F Single conductor, 750 kcmils core-flex services are normally grounded at both ends.
Answer: True if high voltage otherwise False
T or F Before an SCR is fired, it acts like an open circuit
T or F An SCR can only be fired if the polarity on the anode is negative with respect to the cathode.
T or F On a DC drive with the potentiometer adjusted so that the DC motor is turning at minimum speed, the firing angle of the SCR is zero degrees.
T or F High voltage DC lines are not subject to corona.
T or F Single conductor 25 KV URD cables are normally tested at 55 KV.
T or F the autotransformer can be used for starting large motors to increase Torque.
T or F Dynamic braking on a three-phase AC motor is impossible.
T or F Three-phase rectifiers always employ six diodes in their construction.
T or F P.I.V. Is a term used when talking about the forward voltage drop of solid-state devices.
T or F Three-phase bridge rectifiers are normally connected star supplies for full wave operation.
T or F Single conductor URD cables are normally grounded at both ends.
T or F By code, high voltage means 750 Volts or over
Answer: False 751 Volts
T or F On a stress cone the finishing tape is normally wrapped by starting at the lug and taping toward the cone.
T or F The total capacitance of a circuit containing a 20 uF and a 30 uF capacitor connected in series is 50 uF.
Answer : False
T or F There is more line current drawn by a fully loaded five horse power 0.9 PF motor than a 0.7 PF horse power motor.
Answer : False
T or F DC hipot testing is normally done after the cable has been in service for 5 years.
T or F The power factor of a three-phase squirrel cage motor is better at no load than at full load.
T or F URD concentric neutral high voltage cables are used only on three-phase power circuit.
Answer : False
T or F Hypot testing is the only method of testing high voltage equipment.
Answer : False
T or F “Pot heads “ are found only on three conductor P.I.L.C. cable.
T or F A fully charged lead acid batter will have a relative density of 1.125
T or F With a large hard disk drive it is not necessary to back up any file.
T or F In a nurse call system the reset button is located where the incident has happened.
T or F Windows XP is an operating system that is newer than Windows 8 .
T or F Connecting a capacitor in parallel with an inductive AC load will change the line current without affecting the load current.
T or F The speed of a synchronous motor can be controlled by changing the rotor resistance.
Nope it's false
T or F The purpose of a thermocouple in a gas furnace is to indicate the presence of a pilot flame.
T or F The secondary voltage of a delta/wye three phase transformer is in phase with the primary voltage.
T or F A resistor has 3 orange bands, it is a 33 kilohms resistor.
T or F Every 12 revolutions an 8 pole field will generate 48 cycles in a stator winding.
T or F An alternator with 6 pairs of poles generating at 60 Hz would be driven at 600 RPM.
T or F The power of a half-wave single-phase DC circuit can be determined by : ( EDC X 1.11)X(IDC X 1.11) =watts
T or F An “Inductive” load is supplied from an AC source. The current (I) maximum is 310 amps. Voltage (E) maximum is 140 Volts. The effective power In KW supplied to the load is 21.7 KW.
T or F Reactors may be used for limiting fault current surges.
T or F A capacitor put across a set of contacts used in an inductive circuit will act as an arc suppressor.
T or F A 20 kilohms/voltmeter has an insertion circuit resistance of 6 megaohms when switched to a 300 volt scale.
T or F In a series DC circuit containing resistance and capacitance, increasing the capacitance increases the charging time.
T or F To change rotation of any three phase induction motor you simply interchange any two rotor leads.
T or F In a FA system, an E.O.L. ( end of line resistor) is required for electrical supervision.
T or F Power cords have only one proper end to which a power plug may be installed.
Answer : True
T or F The volt amps at the primary of a transformer are greater than the wattage is the secondary.
T or F All three-phase AC motors must have overload protection set at 125% of full load current.
T or F A 20 and 30 uF capacitor are parallel connected to a 200 volt high frequency line. If the total line current to the capacitors is 3 amps, there will be close to 1.9 amps in the 30 uF branch.
T or F The anode is a silicon diode is symbolized by a bar.
T or F Pull boxes used in straight runs of #35 or larger conduit containing 3- #3 R 90 XLPE, shall have a length of at least six times the internal diameter of the conduit.
T or F Amortisseur windings are used to prevent hunting of synchronous alternators.
T or F In general semi conductor material has a positive temperature coefficient.
T or F A thermistor is a power resistor.
T or F It is possible to read the wattage of a balanced three-phase three-wire load employing the two wattmeter method.
T or F In a heat pump the flow of refrigerant can be reversed to supply heating as well as cooling.
T or F When synchronizing AC alternators with the three dark method a considerable difference in voltage could exist even though the lights are dark.
T or F When the frequency to a three-phase Induction motor is reduced by 10% the motor speed will be reduced by 10%
T or F Two 100 KVA transformers connected in open delta will deliver a maximum of 115.4 KVA to a load.
T or F The capacitors in a rapid start ballast are for radio interference and power factor correction only
T or F A diverted rheostat is connected in a series with the series field of a DC generator.
T or F Field discharge resistors in a synchronous motor starter are used to limit field current.
T or F Disconnects are used with high voltage circuit breakers to provide visible proof of voltage isolation.
T or F The purpose if an end of line resistor (EOL) in a supervised fire alarm system is to short circuit the detection devices.
T or F Line loss is found by multiplying the voltage drop and the line current.
T or F The most common word size for a PLC is 2 bytes.
T or F A PLC user memory is factory configured and cannot be changed.
T or F A thermocouple is an example of a discrete I/O
T or F Fail safe wiring refers only to motor control stop circuits.
T or F A PLC can use a 4-20 ma signal as an input ?
To reverse the direction of rotation for a single-phase, shaded pole motor, the :
A.) stator must be removed and turned over
B.) shading coil must be interchanged
C.) starting winding must be interchanged
D.) running winding must be interchanged
Answer: A. Stator must be removed and turned over.
The single-phase, AC series motor has characteristics which are very similar to the :
B.)wound rotor motor
C.) AC squirrel-cage motor
D.) AC induction motor
Answer: A. Universal motor
Which of the following statements is true in Boolean algebra:
A. A•B= A+B
B. — — = ———
D. —— + —- = ———
A. B A+B
Answer : C. A = —
The type of light transmitted in most fibre-optic communications system is:
The greatest drop output voltage will occur if full load is taken from an alternator at:
A.)unity power factor
B.) high leading power factor
C.) low leading power factor
D.) high lagging power factor
Answer: B. High leading power factor .
When a capacitor is charged, the dielectric has :
A.) a surplus of electrons
B.) a deficiency of electrons
C.) the same number of electrons
Answer: C. The same number of electrons.
The best method of controlling the speed of a series motor is to:
A.) change the load
B.) vary the current to the motor
C.) vary the position of the brushes
D.) add a brake drum
Answer: B. Vary the current to the motor
A DC series motor will run away if the load is removed while the power is still being applied. This is a result of:
A.) loss of C.E.M.F
B.) low input voltage to the armature
C.) increased C.E.M.F. acting to weaken the field.
D.) high voltage developed across the field.
Answer: A.loss of C.E.M.F.
Nope it's C
In a delta-star step down transformer bank each transformer has a turns ratio of 2:1 The primary voltage is 480 Volts and the unit supplies a 10 KW, three-phase load at unity power factor. The secondary line current is:
A.) 13.9 amps
B.) 12 amps
C.) 24.1 amps
D.) 36 amps
Answer:C 24.1 amps
HRC fuses are filled with silica to:
A.) make the fuse operate at a lower temperature
B.) speed the rate at which the fuse element melts.
C.) reduce arcing when the fuse element melts
D.) to give a longer time delay
Answer: A. make the fuses operate at a lower temperature.
Nope it's C
If the output voltage of an alternator drops due to heavy loading it is generally brought back up by :
A.) increasing the resistance is the field rheostat
B.) decreasing the resistance of the field rheostat
C.) increasing the speed
D.) decreasing the speed
Answer: C. Increasing the speed
Might be B
A receptacle located in a hospital and connected to the essential electrical equipment shall be :
A.) of the Class “A” GFCI type
B.) approved as hospital grade displaying a green dot or triangle
C.) orange in colour
D.) red In colour
Answer: D. Red in colour
Starting resistances of DC motors are connected:
A.) In the series with the line
B.) In series with the armature
C.) In series with the shunt field
D.) In parallel with the series field
Answer: B. In series with the armature
To determine the state of charge of a nickel-cadmium battery, you could use a :
A.) voltmeter with a load connected to the battery
C.) ammeter with a load connected to the battery
D.) voltmeter to measure the open-circuit voltage
Answer: B. Hydrometer
The specific gravity of the electrolyte in a fully charged nickel-cadmium battery is usually about:
Answer: D. 1200
Emergency systems should be tested:
A.) once a week
B.) once a month
C.) Once every 6 months
D.) Once a year
Answer: B. Once a month
A NO-LOAD terminal voltage of a fully-charged, six cell nickel cadmium battery would measure as:
A. 6 volts
B. 12 volts
C. 13.2 volts
D. 7.2 volts
Answer: D 7.2 volts
A disadvantage of a PV (photovoltaic) system is :
A.) Initial Cost
B.) Maintenance Cost
Answer: A. Initial Cost