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WorksheetsReview unit 6 part-3
Total questions: 64
Worksheet time: 16hrs 0mins
In a snap action overload relay, what happens to the bimetallic strip when heated?
Form into a curved disc
Form into a plate disc
Form into a spiral disc
Form into a straight disc
What happens to a bimetallic temperature switch with snap action if it will be used to make or break large currents needing fast overload response?
The respond quickly
The strip is bonded together
They arc and burn
They are fast to react
Refer to figure below. Identify the operating mechanism of magnetic starter?
Clapper type
Horizontal action type
Bell crank type.
Mechanical Linkage
Refer to figure below. Identify the operating mechanism of magnetic starter?
Clapper type
Horizontal action type
Bell crank type
Mechanical Linkage
Refer to figure below. Identify the operating mechanism of magnetic starter?
Clapper type
Horizontal action type
Bell crank type.
Mechanical Linkage
Using the table , what will be the NEMA starter size for a single phase motor with 15 HP and 240 V?
2
3
4
5
Using the table in Figure 33, what will be the NEMA starter size for a single phase motor with 7 1/2 HP and 208 V?
2
3
4
5
Using the table in Figure 33, what will be the NEMA starter size for a 3 phase motor, 200 HP and 480 V?
2
3
4
5
Using the table in Figure 33, what will be the NEMA starter size for a 3 phase motor, 50 HP and 240 V?
2
3
4
5
Refer the schematic diagram below .what is the eliminate used to keep the start button is holding circuit?
magnetic starter coil
Overload contacts
Auxiliary contact
Latching relay
Refer the schematic diagram below .What will happen if button Start is pressed and released?
MC coil energized ,MC1 contact close and after released MC coil de-energized
MC coil energized ,OL contact open and after released MC coil de-energized
MC coil energized and the circuit remains energized after released
MC coil energized and de-energized
A motor is controlled by a magnetic starter but stops because of an overload, what must be done to operate the motor again?
Keep pressing the start button until the motor runs again
Press the stop and start button repeatedly
Press the start button immediately after the motor stop
Remove the cause of overload and reset the overload contactor
What type of control circuit shown in figure below?
Two-wire control circuit
three-wire control circuit
four-wire control circuit
double -wire control circuit
What type of control circuit, which provides a low voltage release and low voltage protection?
Two-wire control circuit
three-wire control circuit
four-wire control circuit
double -wire control circuit
What type of control circuit which provides a low voltage release but not low voltage protection?
Two-wire control circuit
three-wire control circuit
four-wire control circuit
double -wire control circuit
What does a two wire control circuit provides?
High voltage release and high voltage protection
Low voltage release but not low voltage protection
Low voltage release and low voltage protection
High voltage release but not low voltage protection
What type of control circuit, the control circuit looses power and magnetic starter will de-energized low voltage release?
Two-wire control circuit
three-wire control circuit
four-wire control circuit
double -wire control circuit
What type of control circuit, the coil will dropout and cannot be reset until the voltage returns and stat button is depressed?
Two-wire control circuit
three-wire control circuit
four-wire control circuit
double -wire control circuit
What type of control circuit shown in figure below?
Two-wire control circuit
three-wire control circuit
four-wire control circuit
double -wire control circuit
The start push button is pushed and released, what will happen if the control circuit loses power and restores after a while?
The motor will energize and re-energize
The overload contact will open
The motor will de-energize and re-energize
The motor will de-energize and remain de-energized
Refer to figure below. What will happen if PB2 is pressed and released?
M1 coil will energize and remains energize
M1 coil will energize and then de-energize
M1 coil will de-energize and then energize
M1 coil will energize
What type the circuit that purpose of accomplishing small movements of the driven machine?
Reversing circuit
Jogging circuit
Latching circuit
Interlocking circuit
What type the circuit that used to move machinery small distances at a time example overhead travelling crane?
Reversing circuit
Jogging circuit
Latching circuit
Interlocking circuit
What is the function of PB2 in the circuit?
Serves as the holding circuit
To increase the speed if the driven motors
To keep the equipment running after it is pressed and released
To make small movements on the driven machine
What types of interlocks used in the forward/reversing magnetic starter?
Mechanical
Electrical
Mechanical and electrical
Jogging starter
Refer the figure below. What part of the circuit form electrical interlocks?
F2 & R2
R1 & F1
F2 & R1
R2 &F1
Where is the mechanical interlock located in forward/ reverse motor control circuit that will prevent short circuit Refer the figure above?
At coil F and coil R
At push button PB2 and PB3
At contact F2 and R2
At contact F1 and R1
Refer the figure . What part of the circuit Prevent the motor to run revers when the motor run forward?
F2
F1
R2
R1
Refer the figure . What part of the circuit Prevent the motor to run forward when the motor run reversed?
F2
F1
R2
R1
Refer the figure below. What will happen if Pressed PB2 (Froward)?
F coil will energize , F2 contact closed and F1 contact open the motor run forward
R coil will energize , R2 contact closed and R1 contact open the motor run Reverse
F coil will energize , R2 contact closed and R1 contact open the motor run forward
R coil will de-energize , R2 contact closed and R1 contact open the motor run forward
Refer the figure . What will happen if Pressed PB3 (Reverse)?
F coil will energize , F2 contact closed and F1 contact open the motor run forward
R coil will energize , R2 contact closed and R1 contact open the motor run Reverse
F coil will energize , R2 contact closed and R1 contact open the motor run forward
R coil will de-energize , R2 contact closed and R1 contact open the motor run forward
Refer the figure above. What keeps the forward contactor coil energize after PB2 pressed and released?
F2
F1
R2
R1
Refer the figure . What keeps the Reverse contactor coil energize after PB3 pressed and released?
F2
F1
R2
R1
Refer the figure. Where is the mechanical interlocks located?
F2 & R2 auxiliary contacts
R1 & F1 auxiliary contacts
At F & R contactors coil
R2 &F1 auxiliary contacts
What is the function of the mechanical interlock?
Allows coils F & R to energizing at the same time
Allows de-energizing coils F & R at the same time
Prevents Coils F & R from energizing at the same time
Acts as a holding circuit for Coils F & R
All approved enclosures, boxes and fittings used in hazardous area are called________
Weather proof
Totally Enclosures
Explosive proof
Fire proof
What is the type of conduits used in hazardous locations?
Conduit explosion proof
Flexible meatal conduit
Rigid metal conduit
Electrical meatal tube
Refer the Figure, what is the Parts A, B and C?
A-Seal B- Flexible Fitting C- Flexible Connection
A-Coupling B- Flexible conduit C- Rigid Fittings
A-Seal B-Rigid conduit C- Flexible Fittings
A-Connector B- Flexible conduit C- Flexible Fittings
Refer the Figure . In hazardous area, conduit must be threaded with a standard conduit cutting of _________________inch taper per foot.
½
¾
1
11/2
What must be used to prevent the passage of gas, vapor or flames from one part of the motor control to another through the conduit
Nipple
Threaded reducer
Seals
Explosion proof fittings
In hazardous locations, the conductor must enter the motor through fittings what type of the fittings?
explosion proof rigid fitting
explosion proof Flexible fittings
weather proof rigid fitting
weather proof Flexible fittings
The NEC specified that all boxes and fittings threaded connections must be joined with____________________________
At more five threads engaged
At least five threads engaged
At more six threads engaged
At least seven threads engaged
In hazardous area, what will happen to the lighting fixture if it is replaced by incorrect bulb with higher wattage?
will not operate
break
overheats
nothing will happen
What is the least number of threads must be engaged when making threaded connection of all boxes and fittings?
Five
Six
Three
Four
Why are seals installed on conduit in Hazardous area?
To support conduit in place where it is installed
To allow flammable gas to move from one location to another
To make motor terminations in Hazardous areas
To prevent the passage of flame from one part to another
It is approach or process that you must perform when troubleshooting and finding faults quickly.
disassembly
logical
visual
actual
The power circuit severe faults such as short or ground trip the circuit breaker or blown the fuse, another faults are most likely have tripped the
Relay Control
Timer relay
Overload
magnetic contactor
What is the most probable cause for a circuit breaker to trip?
open circuit
loose connection
Short circuit or ground fault
low voltage
Having a correct voltage in the power supply, where the fault does lies if the magnetic contactor does not energize.
power circuit
control circuit
motor
transformer
If the overload contact does not tripped and the motor control contactor does not energize the fault is probably somewhere in
power circuit
control circuit
motor
transformer
When the control circuit fuse is open, you must check for
loose connection
short circuit
open circuit
power supply
Where does the fault lies if the correct voltage reaches the motor terminal as you press the start button on the control panel?
magnetic contactor main contacts
motor
overload device
magnetic contactor coil
What will happen if there is an overheating of motor stator?
overload device trips
circuit breaker trips
control fuse blows
main disconnect switch opens
What is the symptoms if the motor excessive vibrations?
Fan broken
Shaft bent
Bearing dry
Loose foundation
What is the symptom if the motor not start when energized?
Fan broken
Circuit breaker trips
Bearing dry
Loose foundation
What is the symptom if the motor may be overheating?
Shaft bent
open circuit
Loose foundation
Poor ventilation
What is the Cause the motor to get hotter?
Shaft bent
open circuit
Loose foundation
Lack of lubrication
Lack of lubrication and poor motor ventilation can cause what?
Motor will run quietly
Motor performance will improve
Motor will rotate at faster speed
Motor will overheat
What is the Cause the motor higher temperature and increase frication’s?
Low voltage
Bearing dry
Loose foundation
Shaft bent
What is the possible causing poor intermittent connection or open circuit and motor not operate?
open circuit
loose connection
short circuit
low voltage
What could be the probable cause when the overload device trips?
Fuse blown
loose termination
excessive current
open circuit
What test or fault finding technique are you going to use to check the main contacts of an isolated magnetic contactor if it is working correctly?
short circuit test
current test
continuity test
voltage test
Where will be the fault in a three-wire control circuit if you press the start button the motor runs but as you depressed it the motor stops?
overload device
magnetic contactor holding contact
magnetic contactor coil
start push button contact
Motors mechanical faults includes
stator windings, leads faults
open, shorted terminals
rotor, shaft, bearing, fan failures
grounded motor winding
