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WorksheetsMotor control Week 09
Total questions: 60
Worksheet time: 30mins
What is the purpose of a relay?
To amplify electrical signals
To switch electrical circuits on and off
To filter electrical noise
To measure electrical resistance
What are the maximum voltage and current rating of a relay?
Voltage rating
Current rating
Contact rating
Coil rating
What is the purpose of a latching relay?
To switch electrical circuits on and off
To hold a circuit in a specific state
To amplify electrical signals
To filter electrical noise
When the relay coil is energized, there is a time delay before the contact closes.
On delay NC contact
On delays NO contact
OFF delay NC contact
OFF delays NO contact
When the relay coil is de-energized, there is a time delay before the contact opens.
On delay NC contact
On delays NO contact
OFF delay NC contact
OFF delays NO contact
MCB stands for.
Miniature contact breaker
Main circuit breaker
Miniature circuit breaker
Mini contact breaker
A relay is used to.
Break the fault current
Sense the fault
Sense the fault and direct to trip the circuit breaker
All answers are correct
What is the main component of a relay?
contacts
coil
diode
capacitor
How does a relay work?
By using a mechanical switch
By using a semiconductor technology
By using an electromagnet to activate or deactivate a switch or circuit
By using a resistor to change the current
What are the maximum voltage and current rating of a contactor?
Voltage rating
Current rating
Contact rating
Coil rating
the purpose of a latching relay?
To switch electrical circuits on and off
To hold a circuit in a specific state
To amplify electrical signals
To filter electrical noise
A relay is used to protect a motor from overloading.
Electromechanical relay
Solid state relay
Proximity relay
Overload relay
What is the function of a time-delay relay?
To switch electrical circuits on and off
To hold a circuit in a specific state
To delay the activation or deactivation of a circuit
To filter electrical noise
A relay is used to switch a circuit on and off based on a specific signal or condition.
Control relay
Time-delay relay
Latching relay
Overload relay
protective relays are provided to.
Provide additional safety to the circuit breaker in its operation
Close the contacts when the actuating quantity attains a certain predetermined value
Limit the arcing current during the circuit breaker operation
Earth any stray voltage
Circuit breaker is known as a
Power factor correcting device
device to neutralize the effect of transients
waveform correcting device
current interrupting device
The tripping circuit is__________
AC
DC
Either AC or DC
Inverter
Which of the following element is not used in an automatic control system?
Oscillator
Final control element
Sensor
Error detector
In a control system the output of the controller is given to
Amplifier
Sensor
Final control element
Comparator
identify the contact which is shown below.
Time off delay NC
Time ON delay NC
Time off delay NO
Time ON delay NO
The essential difference between a magnetic motor starter and a magnetic contactor is that the contactor does not contain:
Shading coils
Holding contacts
Overload relay protection
Horsepower-rated contacts
The rotation of an AC three-phase induction motor may be reversed by interchanging:
The control circuit.
The forward/reverse interlocks
The forward reverse coils.
Any two power lines
In a ladder diagram, a dotted line between two coils generally means that the two coils:
Are operated together.
Are mechanically interlocked.
Are electrically interlocked.
Have a common set of contacts.
The _________ PB switch must be connected in parallel with a set of _________ auxiliary contacts on the motor starter to hold the state.
NO Start, NC
NO Start, NO
NC Start, NO
NC Start, NC
The purpose of electrical interlocking in a three-phase reversing AC magnetic motor starter is to:
Ensure that the forward direction of rotation is selected first.
Allow both coils to be energized together.
Prevent both coils from being energized simultaneously.
Maintain the coil circuit after the stop button is released.
The part of a manual AC motor starter which senses motor overload current is the:
High-limit switch
Heater element
Solder-pot assembly
Overload contact
The electrical interlocks in a reversing magnetic starter are:
Normally closed contacts
Normally open contacts
In parallel with the forward and reverse pushbuttons
Controlled by the timing relays necessary for circuit operation.
When the relay coil is de-energized, there is a time delay before the contact opens.
On delay, NC contact
On delay NO contact
OFF delay NC contact
OFF delay NO contact
When the relay coil is energized, there is a time delay before the contact closes.
On delay, NC contact
On delay NO contact
OFF delay NC contact
OFF delay NO contact
When the relay coil is de-energized, there is a time delay before the contact opens.
On delay, NC contact
On delay NO contact
OFF delay NC contact
OFF delay NO contact
When the relay coil is de-energized, there is a time delay before the contact closes.
On delay, NC contact
On delay NO contact
OFF delay NC contact
OFF delay NO contact
What are the maximum voltage and current ratings of a relay?
Voltage rating
Current rating
Contact rating.
Coil rating
Which of the following statements represents the main difference between a relay and a contractor.
Contactors control current, and relays control voltage.
A relay is a series connected, and the contactor is parallel connected.
Contactors can handle heavier loads than relays.
Contactors are made from silver, and relays are made from copper.
Inverters are used to convert.
AC to DC
AC to AC
DC to DC
DC to AC
A component in the oscillator stores the charge for a short time.
Capacitor
Inductor
Relay
transformer
Rectifiers are used to convert.
AC to DC
AC to AC
DC to DC
DC to AC
An ordinarily open type of contact will __________ when it de-energized ________ when it energized.
Close, Open
Open, Close
Open, Open
Closed, Close
Each horizontal line in Ladder Diagram is referred to as:
Period
Group
Rail
Rung
Each vertical line in Ladder Diagram is referred to as:
Period
Group
Rail
Rung
The relays consist of __________
Control circuit
Load circuit
Power circuit
Control and load circuit
Relays is a ___________ device.
Electrical devices
Electromechanical devices
Mechanical devices
Electromagnetic devices
the transformer ratings are expressed in terms of
KW (Kilowatt)
Volts
KVAR (Kilo-Volt-Ampere-Reactive)
KVA (Kilo-Volt-Ampere)
A transformer transforms.
Voltage
Frequency
Current and voltage
Current
A step-up transformer has _____ number of turns on primary winding and _____ number of turns on secondary winding.
Less, More
More, More
More, Less
Less, Less
A step-down transformer has _____ number of turns on primary winding and _____ number of turns on secondary winding.
Less, More
More, More
More, Less
Less, Less
a relay is used to isolate a circuit from another circuit.
Latching relay
Reed relay
solid state relay
Isolation relay
If the coil of a contactor is damaged will act as
Open circuit
Short circuit
Switch
Relay
Contactors are generally designed for switching.
Load Currents
Short circuit currents
No load currents.
Transient Frequency Currents
Motor control circuits can be divided into two major categories, one of which is ____.
Four wires
Three wires
Six wires
Seven wires
All overload relays contain two separate sections, the ____ section and the control contact section.
Current sensing
Contactor contact
Line contact
Load contact
The current-sensing section of the overload relay can be ____, electronic, or thermal.
Electromechanical
Automatic
Manual
Magnetic
In ladder diagrams, line numbers refer to.
Contactors numbers
Terminals numbers
Coils numbers
Phases number
Emergency push buttons are connected.
In series with other stop buttons
In power circuit
In parallel with other stop buttons
Across the coil
use a mechanical latch or permanent magnet to hold the contacts in their last energized position without the need for continued application of coil power.
Timer relay
Latching relay
Overload relay
Control relay
the connection in these motor terminals is.
Delta
Star-Delta
Star
Forward reverse
The figure below demonstrates.
Power circuit only
Control circuit only
Testing points only
Power and control circuit
Which statement is true?
A rectangle in NEMA represents the coil.
A circle in NEMA represents the coil.
A circle represents the coil in IEC.
A square in IEC represents the coil.
In the circuit shown, the light will stay on
if S1 is closed.
For 5 s after coil TD is energized.
For 5 s after the coil TD is de-energized.
For 5 s before the coil TD is de-energized.
If the circuit in the drawing was operating normally and an overload occurred, then.
Both lights would come on
The green light would come on, and the red light would go out.
Both lights would go out
The red light would come on, and the green light would go out.
Identify the contact which is shown below.
Time off delay NC
Time ON delay NC
Time off delay NO
Time ON delay NO
