Temporary repairs to an open DC propulsion armature coil can be made by _____________. A. connecting the coil ends directly to a pair of negative brushes B. disconnecting coil ends, insulating each, and short circuiting the two commutator bars C. grounding the coil ends and short circuiting the commutator bar D. removing the sparking brushes

Temporary repairs to an open DC propulsion armature coil can be made by _____________. A. connecting the coil ends directly to a pair of negative brushes B. disconnecting coil ends, insulating each, and short circuiting the two commutator bars  C. grounding the coil ends and short circuiting the commutator bar D. removing the sparking brushes
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Answer: B
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Related questions

An open armature connection in a DC propulsion motor could be caused by ____________. A. low-load operation B. clogged ventilation ducts C. sparking at the brushes D. a grounded shunt field coil

Description : An open armature connection in a DC propulsion motor could be caused by ____________. A. low-load operation B. clogged ventilation ducts C. sparking at the brushes D. a grounded shunt field coil

Last Answer : Answer: B

The purpose of the commutator and brushes on a DC generator is to _____________. A. transfer generated direct current voltage from the armature to the line B. convert the alternating voltage generated within the armature to a direct voltage C. provide a sliding contact method to excite the field D. reduce sparking between the armature and the carbon brushes

Description : The purpose of the commutator and brushes on a DC generator is to _____________. A. transfer generated direct current voltage from the armature to the line B. convert the alternating voltage ... contact method to excite the field D. reduce sparking between the armature and the carbon brushes

Last Answer : Answer: B

Which of the listed conditions might contribute to very rapid wearing of a DC machine's commutator bars? A. A grounded commutator bar B. Using improper carbon brushes C. Aligning the front and rear mica V-rings improperly D. An open circuit in the armature

Description : Which of the listed conditions might contribute to very rapid wearing of a DC machine's commutator bars? A. A grounded commutator bar B. Using improper carbon brushes C. Aligning the front and rear mica V-rings improperly D. An open circuit in the armature

Last Answer : Answer: B

A flickering ground detection lamp on a DC system would indicate a _____________. A. multiple-ground condition in the distribution system B. ground in an armature coil of an operating machine C. ground in a motor accompanied with a short D. short between two adjacent bars of the generator commutator

Description : A flickering ground detection lamp on a DC system would indicate a _____________. A. multiple-ground condition in the distribution system B. ground in an armature coil of an operating machine C. ground in a motor accompanied with a short D. short between two adjacent bars of the generator commutator

Last Answer : Answer: B

A shorted armature coil in a DC motor can be detected by _____________. A. sparking at the brushes B. shiny armature coil C. worn grooves in the armature D. undercut mica

Description : A shorted armature coil in a DC motor can be detected by _____________. A. sparking at the brushes B. shiny armature coil C. worn grooves in the armature D. undercut mica

Last Answer : Answer: A

Brushes in a generator must be positioned in the neutral plane to avoid sparking between the brushes and the _____________. A. yoke B. armature windings C. field pole windings D. commutator

Description : Brushes in a generator must be positioned in the neutral plane to avoid sparking between the brushes and the _____________. A. yoke B. armature windings C. field pole windings D. commutator

Last Answer : Answer: D

The function of the commutator in a DC motor is to ________. A. reverse the flow of current through the armature B. reverse the flow of current in the field poles C. reduce the reluctance of the magnetic path through the motor D. shift the neutral running plane of the brushes to prevent sparking

Description : The function of the commutator in a DC motor is to ________. A. reverse the flow of current through the armature B. reverse the flow of current in the field poles C. reduce the reluctance of the magnetic path through the motor D. shift the neutral running plane of the brushes to prevent sparking

Last Answer : Answer: A

If you reverse both the field and the armature connections to a DC propulsion motor, _____________. A. the direction of motor rotation will change B. the brushes will become overheated C. a magnetic lock will occur in the motor D. the direction of motor rotation will remain the same

Description : If you reverse both the field and the armature connections to a DC propulsion motor, _____________. A. the direction of motor rotation will change B. the brushes will become overheated C. a magnetic lock will occur in the motor D. the direction of motor rotation will remain the same

Last Answer : Answer: D

A shunt-wound DC generator is one in which the shunt field windings are in parallel with the _____________. A. commutator B. brushes C. armature D. all of the above

Description : A shunt-wound DC generator is one in which the shunt field windings are in parallel with the _____________. A. commutator B. brushes C. armature D. all of the above

Last Answer : Answer: D

Which of the following is a characteristic of fractional horsepower repulsion start motors? A. They start with a rotating stator field. B. The short circuiting ring is removed from the commutator while starting. C. The brushes are removed from the commutator while starting. D. They have a low starting torque.

Description : Which of the following is a characteristic of fractional horsepower repulsion start motors? A. They start with a rotating stator field. B. The short circuiting ring is removed from the commutator while ... brushes are removed from the commutator while starting. D. They have a low starting torque.

Last Answer : Answer: B

Sparking at the brushes of a DC propulsion motor can be the result of ____________. A. improper brush pressure B. improper brush seating C. reversed interpole polarity D. all of the above

Description : Sparking at the brushes of a DC propulsion motor can be the result of ____________. A. improper brush pressure B. improper brush seating C. reversed interpole polarity D. all of the above

Last Answer : Answer: D

Sparking at the brushes of a running motor could be an indication of _____________. A. normal operation B. a dirty commutator C. increased brush capacity D. water vapor absorption

Description : Sparking at the brushes of a running motor could be an indication of _____________. A. normal operation B. a dirty commutator C. increased brush capacity D. water vapor absorption

Last Answer : Answer: B

A short in the shunt field of a DC motor is best located by _____________. A. visual inspection of the commutator B. applying AC voltage to each field coil and measuring the voltage drop across each field coil C. using a growler and hacksaw blade D. isolating each coil from the others and using a megohmmeter

Description : A short in the shunt field of a DC motor is best located by _____________. A. visual inspection of the commutator B. applying AC voltage to each field coil and measuring the voltage drop across ... using a growler and hacksaw blade D. isolating each coil from the others and using a megohmmeter

Last Answer : Answer: B

If only one brush on a commutator is sparking excessively, you should look for _____________. A. a high commutator bar B. copper imbedded in the brush C. a loose commutator bar D. flux in the commutating zone

Description : If only one brush on a commutator is sparking excessively, you should look for _____________. A. a high commutator bar B. copper imbedded in the brush C. a loose commutator bar D. flux in the commutating zone

Last Answer : Answer: B

A short circuit in the armature of a DC motor will cause the motor to _____________. A. run fast B. hum when energized C. spark at the brushes D. fail to start

Description : A short circuit in the armature of a DC motor will cause the motor to _____________. A. run fast B. hum when energized C. spark at the brushes D. fail to start

Last Answer : Answer: C

In general, D.C. propulsion motor brush sparking can be caused by _______________. A. incorrect brush grade, pressure or position B. a concentric commutator C. a dark chocolate colored commutator D. all of the above

Description : In general, D.C. propulsion motor brush sparking can be caused by _______________. A. incorrect brush grade, pressure or position B. a concentric commutator C. a dark chocolate colored commutator D. all of the above

Last Answer : Answer: A

An open in the armature of a DC motor is suspected, but is not found by visual inspection of the commutator. The next step in troubleshooting this problem is to ________________. A. conduct a bar to bar test of the armature B. visually inspect the armature windings C. conduct an insulation resistance test of the armature D. test the commutator for a ground

Description : An open in the armature of a DC motor is suspected, but is not found by visual inspection of the commutator. The next step in troubleshooting this problem is to ________________. A. conduct a ... windings C. conduct an insulation resistance test of the armature D. test the commutator for a ground

Last Answer : Answer: A

Modern DC generators are fitted with commutating poles to _____________. A. prevent motorizing B. reduce sparking C. reduce the load on the main poles D. reduce spring pressure on the brushes

Description : Modern DC generators are fitted with commutating poles to _____________. A. prevent motorizing B. reduce sparking C. reduce the load on the main poles D. reduce spring pressure on the brushes

Last Answer : Answer: B

Which of the listed conditions could cause a DC motor to have excessively hot windings and sparking at the brushes? A. Reversed interpole polarity B. High bar-to-bar voltage C. Loose brushes D. Excessive humidity

Description : Which of the listed conditions could cause a DC motor to have excessively hot windings and sparking at the brushes? A. Reversed interpole polarity B. High bar-to-bar voltage C. Loose brushes D. Excessive humidity

Last Answer : Answer: A

Which of the listed faults cannot be eliminated, EXCEPT by turning or grinding a commutator with a rigidly supported tool? A. Sparking brushes B. Eccentricity C. High mica D. Blackened commutator

Description : Which of the listed faults cannot be eliminated, EXCEPT by turning or grinding a commutator with a rigidly supported tool? A. Sparking brushes B. Eccentricity C. High mica D. Blackened commutator

Last Answer : Answer: B

In an AC generator, direct current from a separate source is passed through the windings of the rotor _____________. A. by means of slip rings and brushes B. by means of a commutator C. by means of rotating bar magnet D. to minimize the danger of arc over

Description : In an AC generator, direct current from a separate source is passed through the windings of the rotor _____________. A. by means of slip rings and brushes B. by means of a commutator C. by means of rotating bar magnet D. to minimize the danger of arc over

Last Answer : Answer: A

In D.C. motor construction, the armature coils' ends are _______________. A. soldered to the commutator bar risers B. imbedded into core slots C. crimped together with brush pigtails D. spliced with the field windings

Description : In D.C. motor construction, the armature coils' ends are _______________. A. soldered to the commutator bar risers B. imbedded into core slots C. crimped together with brush pigtails D. spliced with the field windings

Last Answer : Answer: A

Which of the following are the parts of a DC generator that convert the AC in the armature to DC in the external circuit. Are these parts the: w) field poles x) slip rings and the brushes y) commutator and the brushes z) armature and the core

Description : Which of the following are the parts of a DC generator that convert the AC in the armature to DC in the external circuit. Are these parts the: w) field poles x) slip rings and the brushes y) commutator and the brushes z) armature and the core

Last Answer : ANSWER: Y -- COMMUTATOR AND THE BRUSHES

The purpose of DC generator brushes is to _____________. A. neutralize armature reaction B. conduct electric current to an outside circuit C. convert DC current to AC current D. provide excitation to a DC generator

Description : The purpose of DC generator brushes is to _____________. A. neutralize armature reaction B. conduct electric current to an outside circuit C. convert DC current to AC current D. provide excitation to a DC generator

Last Answer : Answer: B

In addition to undercutting the mica, proper maintenance of a D.C. motor's commutator includes _______________. A. side-cutting the copper segments and insulating the slots B. coating the copper surface with light machine oil for the first four hours of operation C. baking the armature in an oven at a maximum of 95°C for not over 8 hours D. all of the above

Description : In addition to undercutting the mica, proper maintenance of a D.C. motor's commutator includes _______________. A. side-cutting the copper segments and insulating the slots B. coating the copper surface with light machine ... in an oven at a maximum of 95°C for not over 8 hours D. all of the above

Last Answer : Answer: A

Which of the following components are used to convert alternating current produced in the generator windings to direct current? A. Armature and equalizer B. Commutator and brushes C. Rotor and interpoles D. Field and exciter

Description : Which of the following components are used to convert alternating current produced in the generator windings to direct current? A. Armature and equalizer B. Commutator and brushes C. Rotor and interpoles D. Field and exciter

Last Answer : Answer: B

What causes sparking between the brushes and the commutator?

Description : What causes sparking between the brushes and the commutator?

Last Answer : Improper commutation.

Uneven wear of the commutator surface on a direct current propulsion motor can be caused by _____________. A. rapid change in load B. excessive operation at light load C. incorrect brush staggering D. unequal pole spacing

Description : Uneven wear of the commutator surface on a direct current propulsion motor can be caused by _____________. A. rapid change in load B. excessive operation at light load C. incorrect brush staggering D. unequal pole spacing

Last Answer : Answer: C

Insufficient brush pressure on a DC motor may cause _______. A. generator overload B. excess residual magnetism C. water vapor absorption D. sparking of the brushes

Description : Insufficient brush pressure on a DC motor may cause _______. A. generator overload B. excess residual magnetism C. water vapor absorption D. sparking of the brushes

Last Answer : Answer: D

One method of testing for a reversed shunt field coil in a DC generator or motor is by connecting the field to a direct current source, at reduced field rated voltage, and test for polarity using a/an ____________. A. iron bar across each field B. magnetic compass placed near each field C. test lamp across adjacent fields D. copper jumper across the interpole connections

Description : One method of testing for a reversed shunt field coil in a DC generator or motor is by connecting the field to a direct current source, at reduced field rated voltage, and test for ... placed near each field C. test lamp across adjacent fields D. copper jumper across the interpole connections

Last Answer : Answer: B

Brush sparking during commutation may be caused by ________. A. eddy currents in the armature core B. laminations in the generator field pieces C. induced current opposite to coil inductance D. coil inductance discharge occurring at commutation

Description : Brush sparking during commutation may be caused by ________. A. eddy currents in the armature core B. laminations in the generator field pieces C. induced current opposite to coil inductance D. coil inductance discharge occurring at commutation

Last Answer : Answer: D

The rotation of a three-phase induction motor can be reversed by _____________. A. interchanging any two of the three line leads to the stator B. disconnecting one of the three line leads to the stator C. switching the shunt field coil leads D. permanently disconnecting any two of the three line leads to the stator

Description : The rotation of a three-phase induction motor can be reversed by _____________. A. interchanging any two of the three line leads to the stator B. disconnecting one of the three line leads to the ... the shunt field coil leads D. permanently disconnecting any two of the three line leads to the stator

Last Answer : Answer: A

An open occurring within the field rheostat of an AC generator can be detected by short circuiting its terminals and observing a ____________. A. negative deflection of the wattmeter pointer B. positive deflection of the wattmeter pointer C. buildup of alternator voltage D. low, but constant alternator voltage

Description : An open occurring within the field rheostat of an AC generator can be detected by short circuiting its terminals and observing a ____________. A. negative deflection of the wattmeter pointer B. ... of the wattmeter pointer C. buildup of alternator voltage D. low, but constant alternator voltage

Last Answer : Answer: C

Sparking of D.C. motor brushes can be caused by __________. A. an open commutating winding B. many mechanical, electrical or operating faults C. an open interpole D. all of the above

Description : Sparking of D.C. motor brushes can be caused by __________. A. an open commutating winding B. many mechanical, electrical or operating faults C. an open interpole D. all of the above

Last Answer : Answer: B

An open shunt field in a direct current machine may be located by connecting the field circuit to an external power source, equal to the rated field voltage or less, and tested with a voltmeter from _____________. A. one line terminal to each coil lead in succession B. one field coil to each adjacent field coil in turn C. any suitable ground to any available line lead D. any field pole to each field coil lead

Description : An open shunt field in a direct current machine may be located by connecting the field circuit to an external power source, equal to the rated field voltage or less, and tested with a voltmeter from ... C. any suitable ground to any available line lead D. any field pole to each field coil lead

Last Answer : Answer: A

Armature coil is short circuited by brushes when it lies?

Last Answer : Armature coil is short circuited by brushes when it lies along neutral axis.

The direction of rotation of a DC propulsion motor can be reversed by __________. A. reversing the field connections B. reversing the field and the armature connections C. wiring the field and armature in parallel D. wiring the field and armature in series

Description : The direction of rotation of a DC propulsion motor can be reversed by __________. A. reversing the field connections B. reversing the field and the armature connections C. wiring the field and armature in parallel D. wiring the field and armature in series

Last Answer : Answer: A

Why grounding mat is important near ground switch operating handle and disconnecting switch operating handle?

Description : Why grounding mat is important near ground switch operating handle and disconnecting switch operating handle?

Last Answer : Equipment operating handles deserve special attention because of the higher probability for co-incidence of adverse factors. For example, a. Hand operation equipment such as grounding switches and disconnecting ... both in order to bring down the values of touch potential and step potential.  

If a DC motor runs faster than designed, with all other conditions being normal, the possible cause could be a/an ______________. A. shorted shunt field coil B. open armature coil C. reversed commutating pole D. overload

Description : If a DC motor runs faster than designed, with all other conditions being normal, the possible cause could be a/an ______________. A. shorted shunt field coil B. open armature coil C. reversed commutating pole D. overload

Last Answer : Answer: A

For routine cleaning of a commutator, you should apply _____________. A. course sandpaper in a slow back and forth motion across the commutator slots B. an emery cloth parallel to the axis of the machine C. a canvas wiper to the machine while running D. cotton swabs between the commutator bars

Description : For routine cleaning of a commutator, you should apply _____________. A. course sandpaper in a slow back and forth motion across the commutator slots B. an emery cloth parallel to the axis of the machine C. a canvas wiper to the machine while running D. cotton swabs between the commutator bars

Last Answer : Answer: C

In testing a three-phase delta winding for an open circuit using a megohmmeter, you must ______________. A. test each phase with all connections intact B. measure the voltage across the open connections while testing C. test the windings as parallel groups to avoid short circuiting D. open the delta-connections to avoid shunting the phase being tested

Description : In testing a three-phase delta winding for an open circuit using a megohmmeter, you must ______________. A. test each phase with all connections intact B. measure the voltage across the open ... groups to avoid short circuiting D. open the delta-connections to avoid shunting the phase being tested

Last Answer : Answer: D

Hysteresis in a direct current generator is indicated by _____________. A. arcing at the brushes B. pulsating terminal current C. heating of the armature core D. hunting and over control

Description : Hysteresis in a direct current generator is indicated by _____________. A. arcing at the brushes B. pulsating terminal current C. heating of the armature core D. hunting and over control

Last Answer : Answer: C

In an induction motor, rotor currents are circulated in the rotor by _____________. A. slip rings and brushes B. an armature and brushes C. inductive reaction of the rotating stator field D. external variable resistors

Description : In an induction motor, rotor currents are circulated in the rotor by _____________. A. slip rings and brushes B. an armature and brushes C. inductive reaction of the rotating stator field D. external variable resistors

Last Answer : Answer: C

The most effective method of locating a loose commutator bar in a D.C. motor is by _____________. A. visual inspection B. jiggling each by hand C. sounding each bar with a light weight hammer D. checking with a calibrated torque wrench

Description : The most effective method of locating a loose commutator bar in a D.C. motor is by _____________. A. visual inspection B. jiggling each by hand C. sounding each bar with a light weight hammer D. checking with a calibrated torque wrench

Last Answer : Answer: C

Which of the listed conditions will occur if the polarity of the field poles and the direction of current to the brushes of a DC motor were both reversed? A. The motor would not start. B. The direction of rotation of the armature would be reversed. C. The direction of rotation of the armature would be unchanged. D. The field pole windings would become overheated.

Description : Which of the listed conditions will occur if the polarity of the field poles and the direction of current to the brushes of a DC motor were both reversed? A. The motor would not start. ... direction of rotation of the armature would be unchanged. D. The field pole windings would become overheated.

Last Answer : Answer: C

Which of the following statements describes what will happen when both the polarity of the field poles, and the direction of current to the brushes of a DC motor are reversed? A. The motor will not start. B. The direction of rotation of the armature will be reversed. C. The direction of rotation of the armature will remain the same. D. The field pole windings will become overheated.

Description : Which of the following statements describes what will happen when both the polarity of the field poles, and the direction of current to the brushes of a DC motor are reversed? A. The motor will ... of rotation of the armature will remain the same. D. The field pole windings will become overheated.

Last Answer : Answer: C

Propulsion DC motor brush pressures can be calculated by _____________. A. dividing the brush contact area by the spring pressure B. subtracting the brush contact area from the spring pressure C. dividing the spring force by the brush contact area D. subtracting the spring pressure from the brush contact area

Description : Propulsion DC motor brush pressures can be calculated by _____________. A. dividing the brush contact area by the spring pressure B. subtracting the brush contact area from the spring pressure C. ... force by the brush contact area D. subtracting the spring pressure from the brush contact area

Last Answer : Answer: C

The direction of rotation of a DC propulsion motor can be changed by reversing the _____________. A. brush holder position B. polarity of the field poles C. brush staggered order D. motor interpole connections

Description : The direction of rotation of a DC propulsion motor can be changed by reversing the _____________. A. brush holder position B. polarity of the field poles C. brush staggered order D. motor interpole connections

Last Answer : Answer: B