What is the significance of frame size of motor?

What is the significance of frame size of motor?
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In order to make practical choice, interchangeability and large scale production possible. 
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Why back emf used for a dc motor? highlight its significance.

Description : Why back emf used for a dc motor? highlight its significance.

Last Answer : The induced emf developed when the rotating conductors of the armature between the poles of magnet, in a DC motor, cut the magnetic flux, opposes the current flowing through the conductor, when the ... speed of rotation of the armature conductors. In starting, the value of back emf is zero.

When using a megohmmeter to determine which shunt field coil is grounded in a DC machine, you must ____________. A. insulate the field frame from the ship's hull B. disconnect each shunt field coil before testing C. use a motor driven high capacity megohmmeter D. remove all main line lead connections before testing

Description : When using a megohmmeter to determine which shunt field coil is grounded in a DC machine, you must ____________. A. insulate the field frame from the ship's hull B. disconnect each shunt ... C. use a motor driven high capacity megohmmeter D. remove all main line lead connections before testing

Last Answer : Answer: B

To protect the rotor of a motor disassembled for maintenance or overhaul, it should be ___________________. A. suspended by wire slings in one corner of the shop B. stowed upright on its shaft C. supported by two 'V' notched wood blocks D. returned to the frame as soon as the bearings are removed

Description : To protect the rotor of a motor disassembled for maintenance or overhaul, it should be ___________________. A. suspended by wire slings in one corner of the shop B. stowed upright on its shaft C. supported by two 'V' notched wood blocks D. returned to the frame as soon as the bearings are removed

Last Answer : Answer: C

Some large A.C. motors are equipped with with heaters. These could be ___________. I. resistance heaters bolted directly to the frame II. low voltage windings embedded in the motor windings A. I only B. II only C. either I or II D. neither I or II

Description : Some large A.C. motors are equipped with with heaters. These could be ___________. I. resistance heaters bolted directly to the frame II. low voltage windings embedded in the motor windings A. I only B. II only C. either I or II D. neither I or II

Last Answer : Answer: C

An electrical connection between the wiring of an electric motor and its metal frame is known as a/an _____________. A. eddy current B. ground C. impedance D. flux leakage

Description : An electrical connection between the wiring of an electric motor and its metal frame is known as a/an _____________. A. eddy current B. ground C. impedance D. flux leakage

Last Answer : Answer: B

To protect the rotor of a motor disassembled for maintenance or overhaul, it should be ___________________. A. suspended by wire slings in one corner of the shop B. wrapped in several layers of heavy paper or cardboard C. supported by flat wood blocks on the workbench D. returned to the frame as soon as the bearings are removed

Description : To protect the rotor of a motor disassembled for maintenance or overhaul, it should be ___________________. A. suspended by wire slings in one corner of the shop B. wrapped in several layers of heavy ... flat wood blocks on the workbench D. returned to the frame as soon as the bearings are removed

Last Answer : Answer: B

One of the generator or motor bearings is generally insulated from the end housing in order to prevent ________. A. rapid brush wear B. current leakage from the shaft C. excessive field winding heat D. circulation of shaft currents induced in the machine's frame

Description : One of the generator or motor bearings is generally insulated from the end housing in order to prevent ________. A. rapid brush wear B. current leakage from the shaft C. excessive field winding heat D. circulation of shaft currents induced in the machine's frame

Last Answer : Answer: D

In the illustrated motor, roller bearings are used because __________. EL-0001 A. of their ability to absorb moderate thrust loads B. they electrically insulate the rotor from the frame reducing cross-currents C. the shafting and end bells do not require as close a tolerance to properly fit this type of bearing D. the clearance between the rotor and stator is generally as close as mechanical tolerance will permit

Description : In the illustrated motor, roller bearings are used because __________. EL-0001 A. of their ability to absorb moderate thrust loads B. they electrically insulate the rotor from the frame reducing ... clearance between the rotor and stator is generally as close as mechanical tolerance will permit

Last Answer : Answer: D

In a compound-wound motor, a portion of the line current flows through the _____________. A. inertial poles B. stator C. shunt field coils D. frame

Description : In a compound-wound motor, a portion of the line current flows through the _____________. A. inertial poles B. stator C. shunt field coils D. frame

Last Answer : Answer: C

The purpose of squirrel-cage windings in a synchronous motor is to ______________. A. provide more precise balancing B. produce a higher power factor C. eliminate arcing between the stator and the frame D. provide a means for starting

Description : The purpose of squirrel-cage windings in a synchronous motor is to ______________. A. provide more precise balancing B. produce a higher power factor C. eliminate arcing between the stator and the frame D. provide a means for starting

Last Answer : Answer: D

What is back emf in DC motor? Explain its significance.

Last Answer : Back emf: When the armature of DC motor rotates under the fixed magnetic field and cuts it, by Faraday's law an emf is induced in them. The induced emf acts in opposite direction to the ... the flow of armature current i.e. it automatically changes the armature current to meet load requirements. 

Which of the following statements describes the significance of ambient temperature in relation to the service life of electronic components? A. Ambient temperature should be as high as possible to drive off moisture. B. Increased ambient temperature decreases the service life of electronic components. C. Ambient temperature is not significant as long as the relative humidity is kept low. D. A reduced ambient temperature causes a corresponding reduced service life.

Description : Which of the following statements describes the significance of ambient temperature in relation to the service life of electronic components? A. Ambient temperature should be as high as possible to drive ... is kept low. D. A reduced ambient temperature causes a corresponding reduced service life.

Last Answer : Answer: B

What is the significance of Corona rings in substations?

Description : What is the significance of Corona rings in substations?

Last Answer : It is observed that corona discharge occurs mostly at sharp corners, edges near the conductor fixing points. Corona rings also called grading rings are hallow metallic rings having large diameter ... is reduced to much lower value Corona discharge is eliminated Dust deposition is also minimized

What are Test signals and their significance?

Description : What are Test signals and their significance?

Last Answer : The knowledge of the input signal is required to predict the response of the system. In most of the systems input signals are not known ahead of the time and it is also difficult to ... the control system. The commonly used test signals are impulse, ramp, step signals and sinusoidal signals.

What is S-domain and its significance?

Description : What is S-domain and its significance?

Last Answer : By taking Laplace transform for differential equation in the time domain equations in S-domain can be obtained. L{F(t)}=F(s) S domain is used for solving the time domain differential equations easily by applying the Laplace for the differential equations.

What is the significance of vector grouping in Power Transformers?

Description : What is the significance of vector grouping in Power Transformers?

Last Answer : Every power transformer has a vector group listed by its manufacturer. Fundamentally it tells you the information about how the windings are connected (delta or wye) and the phase difference between the ... Delta primary, Wye Secondary and the current is at 11 o clock referred to the voltage.

What is the significance of vector grouping in Power Transformers?

Description : What is the significance of vector grouping in Power Transformers?

Last Answer : A: Every power transformer carries a vector group listed by its manufacturer. Fundamentally it tells you the information about how the windings are connected (delta or wye) and the phase difference between ... Delta primary, Wye Secondary and the current is at 11 o clock referred to the voltage.

What is the significance of vector grouping in Power Transformers?

Description : What is the significance of vector grouping in Power Transformers?

Last Answer : Answer:Every power transformer has a vector group listed by its manufacturer. Fundamentally it tells you the information about how the windings are connected (delta or wye) and the phace difference betweent ... Delta primary, Wye Secondry and the current is at 11 o clock reffered to the voltage.

What is the significance of vector grouping in Power Transformers?

Description : What is the significance of vector grouping in Power Transformers?

Last Answer : A. Every power transformer has a vector group listed by its manufacturer. Fundamentally it tells you the information about how the windings are connected (delta or wye) and the phase difference between the ... Delta primary, Wye Secondary and the current is at 11 o clock referred to the voltage.

What Is Buchholz Relay And The Significance Of It In To The transformer ?

Description : What Is Buchholz Relay And The Significance Of It In To The transformer ?

Last Answer : Buchholz Relay is a device which is used for the protection of transformer from its internal faults, it is a gas based relay. whenever any internal fault occurs in a transformer, the Buchholz Relay ... then it stop its sound itself other wise it trips the circuit by its own tripping mechanism.

What is buchholz relay and the significance of it in to the transformer?

Description : What is buchholz relay and the significance of it in to the transformer?

Last Answer : A:Buchholz relay is a gas based relay which is used for the protection of transformer from its internal faults. whenever any internal fault occurs in a transformer, the buchholz relay at once gives an ... then it stop its sound itself other wise it trips the circuit by its own tripping mechanism.

Write the significance of load factor?

Description : Write the significance of load factor?

Last Answer : Higher load factor means greater average load, resulting in greater number of units generated for a given maximum demand. Thus, the standing charges, which are proportional to maximum demand ... units supplied and therefore overall cost per unit of electrical energy generated will be reduced.

what is Buchholz relay and the significance of it in to the transformer?

Description : what is Buchholz relay and the significance of it in to the transformer?

Last Answer : Buchholz relay is a device which is used for the protection of transformer from its internal faults, it is a gas based relay. whenever any internal fault occurs in a transformer, the Buchholz ... circuit then it stop its sound itself otherwise it trips the circuit by its own tripping mechanism.

State the significance of double line fault.

Description : State the significance of double line fault.

Last Answer : It has no zero sequence component and the positive and negative sequence networks are connected in parallel.

State the significance of single line to ground fault.

Description : State the significance of single line to ground fault.

Last Answer : In single line to ground fault all the sequence networks are connected in series. All the sequence currents are equal and the fault current magnitude is three times its sequence currents.

What is the significance of SF6 gas pressure in 6.6kV breakers?

Description : What is the significance of SF6 gas pressure in 6.6kV breakers?

Last Answer : Density gauge Green – correct SF6 pressure (3 –3.5bar) Yellow – pressure for breaking system fault current (refilling should be done) Red – SF6 pressure less than 2 bar, which indicates leak in the system. 

What are the levels of SF6 gas in 220 kV breaker and their significance?

Description : What are the levels of SF6 gas in 220 kV breaker and their significance?

Last Answer : 7 kg/cm2 - normal pressure 5.2 bar - alarm 5.0 bar - closing/tripping operation blocked. 

What is size of shaded-pole motor?

Description : What is size of shaded-pole motor?

Last Answer : These are usually built in small fractional H.P, not exceed 1/4 H.P.

State the function of following parts of slip ring induction motor: (i) Slip ring (ii) Fan (iii) Brushes (iv) Frame

Description : State the function of following parts of slip ring induction motor: (i) Slip ring (ii) Fan (iii) Brushes (iv) Frame

Last Answer : Sr. No. Name of part Function 1 Slip ring 1) The rotor winding terminals are permanently connected to the slip rings. 2) Connects external resistance to rotor circuit through ... It provides mechanical support to the entire internal parts of motor. 2) Protects the inner parts.

When disassembling electric motors for maintenance or overhaul, ________________. A. punch mark frame and end bells for proper assembly B. wrap bearings in lint free cloths if they are to be reused C. tag and store small parts in a box D. all of the above

Description : When disassembling electric motors for maintenance or overhaul, ________________. A. punch mark frame and end bells for proper assembly B. wrap bearings in lint free cloths if they are to be reused C. tag and store small parts in a box D. all of the above

Last Answer : Answer: D

To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the ____________________. A. power supply B. variable resistor C. frame of the machine D. armature

Description : To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the ____________________. A. power supply B. variable resistor C. frame of the machine D. armature

Last Answer : Answer: C

Armature cores in a DC generator are made of laminated steel sheets to _____________. A. fit the curvature of the frame B. increase the hysteresis effect C. reduce eddy current losses D. allow for easy assembly

Description : Armature cores in a DC generator are made of laminated steel sheets to _____________. A. fit the curvature of the frame B. increase the hysteresis effect C. reduce eddy current losses D. allow for easy assembly

Last Answer : Answer: C

In electronic circuits, DC voltages can be positive (+) or negative (-) when measured with respect to the _________. A. printed circuit board 'common' trace B. chassis, console frame or hull 'ground' C. analogue or digital circuitry 'common' bus D. all of the above

Description : In electronic circuits, DC voltages can be positive (+) or negative (-) when measured with respect to the _________. A. printed circuit board 'common' trace B. chassis, console frame or hull 'ground' C. analogue or digital circuitry 'common' bus D. all of the above

Last Answer : Answer: D

How do you know what size frame to use for a photo?

Description : How do you know what size frame to use for a photo?

Last Answer : Normally with photo frames the size refers to the size of the picture opening and not the exterior dimensions of the frame. In the United States, picture frame sizes are always measured in inches. In most other parts of the world they are measured in centimeters.

What picture frame comes with customizable features such as being able to expand it's size?

Description : What picture frame comes with customizable features such as being able to expand it's size?

Last Answer : The Philips 9FF2M4 digital photo frame has some of the best customizable features. The frame comes standard with a white frame along with three extra colored frames: red, silver, and black. The unit automatically resizes pictures to fit to the screen. You can add labels to pictures.

Is it possible to center an object horizontally in a repeating frame that has a variable horizontal size?

Description : Is it possible to center an object horizontally in a repeating frame that has a variable horizontal size?

Last Answer : Yes

______ eliminates the varying delay times associated withdifferent-size packets. A) X.25 B) Frame Relay C) ATM D) all of theabove

Description : ______ eliminates the varying delay times associated withdifferent-size packets. A) X.25 B) Frame Relay C) ATM D) all of theabove

Last Answer : ATM

A _______is defined as a small, fixed-size block of information. A) frame B) packet C) cell D) none of the above

Description : A _______is defined as a small, fixed-size block of information. A) frame B) packet C) cell D) none of the above

Last Answer : cell

Which of the following technique isused for encapsulation? A. a technique used inbest-effort delivery systems toavoid endlessly loopingpackets. B. a technique used by protocols in which a lower level protocol accepts a message from ahigher level protocol and places it in the data portion of the low level frame. C. One of the pieces that results when an IP gateway divides an IP datagram into smallerpieces for transmission acrossa network that cannothandle the originaldatagram size D. All of theabove E. None of the above

Description : Which of the following technique isused for encapsulation? A. a technique used inbest-effort delivery systems toavoid endlessly loopingpackets. B. a technique used by protocols in which a lower level ... network that cannothandle the originaldatagram size D. All of theabove E. None of the above

Last Answer : a technique used by protocols in which a lower level protocol accepts a message from ahigher level protocol and places it in the data portion of the low level frame

Which of the following technique isused for fragment? A. a technique used inbest-effort delivery systems toavoid endlessly loopingpackets B. a technique used by protocols in which a lower level protocol accepts a message from ahigher level protocol and places it in the data portion of the low level frame C. one of the pieces that results when an IP gateway divides an IP datagram into smallerpieces for transmission acrossa network that cannothandle the originaldatagram size D. All of theabove E. None of the above

Description : Which of the following technique isused for fragment? A. a technique used inbest-effort delivery systems toavoid endlessly loopingpackets B. a technique used by protocols in which a lower level protocol ... network that cannothandle the originaldatagram size D. All of theabove E. None of the above

Last Answer : one of the pieces that results when an IP gateway divides an IP datagram into smallerpieces for transmission acrossa network that cannothandle the originaldatagram size

the maximum window size for data transmission using the selective reject protocol with n-bit frame sequence numbers is: a. 2^n b. 2^(n-1) c. 2^n – 1 d. 2^(n-2)

Description : the maximum window size for data transmission using the selective reject protocol with n-bit frame sequence numbers is: a. 2^n b. 2^(n-1) c. 2^n – 1 d. 2^(n-2)

Last Answer : b. 2^(n-1)

Suppose that the one-way propagation delay for a 100 Mbps Ethernet having 48-bit jamming signal is 1.04 micro-seconds. The minimum frame size in bits is: a. 112 b. 160 c. 208 d. 256

Description : Suppose that the one-way propagation delay for a 100 Mbps Ethernet having 48-bit jamming signal is 1.04 micro-seconds. The minimum frame size in bits is: a. 112 b. 160 c. 208 d. 256

Last Answer : d. 256

The minimum frame size required for a CSMA/CD based computer network running at 1 Gbps on a 200m cable with a link speed of 2 × 108m/s is a. 125 bytes b. 250 bytes c. 500 bytes d. None of these

Description : The minimum frame size required for a CSMA/CD based computer network running at 1 Gbps on a 200m cable with a link speed of 2 × 108m/s is a. 125 bytes b. 250 bytes c. 500 bytes d. None of these

Last Answer : b. 250 bytes

In an Ethernet local area network, which one of the following statements is TRUE ? a. A station stops to sense the channel once it starts transmitting a frame. b. The purpose of the jamming signal is to pad the frames that are smaller than the minimum frame size. c. A station continues to transmit the packet even after the collision is detected. d. The exponential backoff mechanism reduces the probability of collision on retransmissions

Description : In an Ethernet local area network, which one of the following statements is TRUE ? a. A station stops to sense the channel once it starts transmitting a frame. b. The purpose ... collision is detected. d. The exponential backoff mechanism reduces the probability of collision on retransmissions

Last Answer : The exponential backoff mechanism reduces the probability of collision on retransmissions

A sender uses the Stop-and-Wait ARQ protocol for reliable transmission of frames. Frames are of size 1000 bytes and the transmission rate at the sender is 80 Kbps (1Kbps = 1000 bits/second). Size of an acknowledgement is 100 bytes and the transmission rate at the receiver is 8 Kbps. The one-way propagation delay is 100 milliseconds. Assuming no frame is lost, the sender throughput is __________ bytes/second. a. 2500 b. 2000 c. 1500 d. 500

Description : A sender uses the Stop-and-Wait ARQ protocol for reliable transmission of frames. Frames are of size 1000 bytes and the transmission rate at the sender is 80 Kbps (1Kbps = 1000 bits/second). Size of ... is lost, the sender throughput is __________ bytes/second. a. 2500 b. 2000 c. 1500 d. 500

Last Answer : a. 2500

Consider a CSMA/CD network that transmits data at a rate of 100 Mbps (108 bits per second) over a 1 km (kilometre) cable with no repeaters. If the minimum frame size required for this network is 1250 bytes, what is the signal speed (km/sec) in the cable? a. 8000 b. 10000 c. 16000 d. 20000

Description : Consider a CSMA/CD network that transmits data at a rate of 100 Mbps (108 bits per second) over a 1 km (kilometre) cable with no repeaters. If the minimum frame size required for this network is 1250 bytes, what is the signal speed (km/sec) in the cable? a. 8000 b. 10000 c. 16000 d. 20000

Last Answer : d. 20000

Suppose the round trip propagation delay for a 10 Mbps Ethernet having 48-bit jamming signal is 46.4 ms. The minimum frame size is a. 94 b. 416 c. 464

Description : Suppose the round trip propagation delay for a 10 Mbps Ethernet having 48-bit jamming signal is 46.4 ms. The minimum frame size is a. 94 b. 416 c. 464

Last Answer : c. 464