During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points

During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points
by

1 Answer

Answer :

Answer: B
by

Related questions

When troubleshooting motor controllers, a shorted relay or contactor coil is often indicated by _______________. A. a resistance reading of 'infinity' on an ohmmeter B. charred insulation and/or a blown control fuse C. a reading of 'zero' on a megger from one of the coil's leads to ground D. a higher-than-normal voltage reading across the winding

Description : When troubleshooting motor controllers, a shorted relay or contactor coil is often indicated by _______________. A. a resistance reading of 'infinity' on an ohmmeter B. charred insulation and/or a blown ... of the coil's leads to ground D. a higher-than-normal voltage reading across the winding

Last Answer : Answer: B

A loud buzzing noise in an AC controller is probably caused by _____________. A. poor contact with the overload relay B. an incorrectly sized heater C. a broken shading coil D. abnormal starting current

Description : A loud buzzing noise in an AC controller is probably caused by _____________. A. poor contact with the overload relay B. an incorrectly sized heater C. a broken shading coil D. abnormal starting current

Last Answer : Answer: C

Humming or buzzing of electric contacts is a symptom of ____________. A. low voltage on the operating coil B. power failure to the operating coil C. a control circuit ground D. a control circuit overload

Description : Humming or buzzing of electric contacts is a symptom of ____________. A. low voltage on the operating coil B. power failure to the operating coil C. a control circuit ground D. a control circuit overload

Last Answer : Answer: A

If a magnetic controller contactor fails to pick up when the coil voltage is applied to the contactor coil, the cause may be _____________. A. overload B. misalignment of the affected contactor contacts C. low spring pressure D. an open contactor coil

Description : If a magnetic controller contactor fails to pick up when the coil voltage is applied to the contactor coil, the cause may be _____________. A. overload B. misalignment of the affected contactor contacts C. low spring pressure D. an open contactor coil

Last Answer : Answer: D

A loud buzzing noise at the contacts of a magnetic controller could indicate _____________. A. weak contact spring pressure B. misalignment of the magnet faces C. excessive line current D. mechanical binding

Description : A loud buzzing noise at the contacts of a magnetic controller could indicate _____________. A. weak contact spring pressure B. misalignment of the magnet faces C. excessive line current D. mechanical binding

Last Answer : Answer: B

A loud buzzing noise coming from the contacts in a magnetic controller can be caused by ____________. A. excessive current B. excessive magnet gap C. bouncing of contacts D. dirt on magnet faces

Description : A loud buzzing noise coming from the contacts in a magnetic controller can be caused by ____________. A. excessive current B. excessive magnet gap C. bouncing of contacts D. dirt on magnet faces

Last Answer : Answer: D

Magnetic controller contacts may become welded together during operation because of _____________. A. excessive magnetic gap B. low contact pressure C. an open coil D. excessive ambient temperature

Description : Magnetic controller contacts may become welded together during operation because of _____________. A. excessive magnetic gap B. low contact pressure C. an open coil D. excessive ambient temperature

Last Answer : Answer: B

Magnetic controller contacts may become welded together during operation due to _____________. A. an open coil B. low contact pressure C. excessive ambient temperature D. excessive magnetic gap

Description : Magnetic controller contacts may become welded together during operation due to _____________. A. an open coil B. low contact pressure C. excessive ambient temperature D. excessive magnetic gap

Last Answer : Answer: B

A shading coil used in an AC magnetic controller, functions to _____________. A. reduce vibration and noise in the contactor B. prevent flux buildup in the operating coil C. eliminate arcing when the contacts close D. energize the operating coil and 'pull in' the contacts

Description : A shading coil used in an AC magnetic controller, functions to _____________. A. reduce vibration and noise in the contactor B. prevent flux buildup in the operating coil C. eliminate arcing when the contacts close D. energize the operating coil and 'pull in' the contacts

Last Answer : Answer: A

Magnet chatter or 'pumping' occurring in a magnetic contactor can be caused by ______________. A. dirt or grease on pole faces B. mechanical interference in the contacts C. chattering contacts on the control relay D. magnetic lock out of the contacts

Description : Magnet chatter or 'pumping' occurring in a magnetic contactor can be caused by ______________. A. dirt or grease on pole faces B. mechanical interference in the contacts C. chattering contacts on the control relay D. magnetic lock out of the contacts

Last Answer : Answer: C

The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains _____________. A. a magnetic operating coil B. normally open line contacts C. thermal-overload protection D. a momentary-contact start button

Description : The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains _____________. A. a magnetic operating coil B. normally open line contacts C. thermal-overload protection D. a momentary-contact start button

Last Answer : Answer: D

When troubleshooting a magnetic controller, it is found that the contacts are welded together. The most probable cause is _____________. A. excessive operation at low load B. high ambient temperature C. low voltage on the operating coil D. high voltage on the operating coil

Description : When troubleshooting a magnetic controller, it is found that the contacts are welded together. The most probable cause is _____________. A. excessive operation at low load B. high ambient temperature C. low voltage on the operating coil D. high voltage on the operating coil

Last Answer : Answer: C

A circuit is protected from overheating by a/an ___________. A. pyrometer B. thermal overload relay C. magnetic contactor D. overload transformer

Description : A circuit is protected from overheating by a/an ___________. A. pyrometer B. thermal overload relay C. magnetic contactor D. overload transformer

Last Answer : Answer: B

Magnetic controller contacts may become welded together during operating conditions as a result of _____________. A. high spring pressure B. high ambient temperature C. an open coil D. low voltage on operating coil

Description : Magnetic controller contacts may become welded together during operating conditions as a result of _____________. A. high spring pressure B. high ambient temperature C. an open coil D. low voltage on operating coil

Last Answer : Answer: D

The winch shown in the illustration operates in any of the positions with the master switch in the 'lower' direction, but will not 'hoist' in any of the master switch hoist positions. Which of the listed faults could be the cause? EL-0102 A. Master switch contact 'MS3' may have defective springs. B. Contactor '3M' coil could have an open winding. C. Contact '2M' in the power circuit may be badly corroded. D. Series relay 'FR' may be open.

Description : The winch shown in the illustration operates in any of the positions with the master switch in the 'lower' direction, but will not 'hoist' in any of the master switch hoist positions. Which of the listed faults ... '2M' in the power circuit may be badly corroded. D. Series relay 'FR' may be open.

Last Answer : Answer: A

If a magnetic controller relay fails to drop out when the coil voltage is removed from the relay, the probable cause may be _____________. A. excessive spring tension B. overvoltage C. excessive current D. welded contacts

Description : If a magnetic controller relay fails to drop out when the coil voltage is removed from the relay, the probable cause may be _____________. A. excessive spring tension B. overvoltage C. excessive current D. welded contacts

Last Answer : Answer: D

When an operating motor is connected to the controller shown in the illustration, the a path of current flow through the circuit is ____________. EL-0010 A. 'L1', stop button, start button, coil 'CR', 'L2' B. 'L1', stop button, 'CR' and 'M' contacts, 'M' coil, 'OL contacts, the 'CR' coil in parallel, 'L2' C. 'L1', stop button, jog button, 'CR' contact, 'CR' relay, 'L2' D. 'L1', stop button, start button, 'CR' contact, 'M' contact, 'CR' coil, 'L2'

Description : When an operating motor is connected to the controller shown in the illustration, the a path of current flow through the circuit is ____________. EL-0010 A. 'L1', stop button, start button, coil 'CR', 'L2' B. 'L1' ... L2' D. 'L1', stop button, start button, 'CR' contact, 'M' contact, 'CR' coil, 'L2'

Last Answer : Answer: B

If you hear a loud buzzing noise coming from a magnetic motor controller, you should ____________. A. assume that the motor is operating at a full load B. assume that the controller is operating normally C. notify the electrician or watch engineer of the problem D. feel the outside of the casing with your hand to see if it is hot

Description : If you hear a loud buzzing noise coming from a magnetic motor controller, you should ____________. A. assume that the motor is operating at a full load B. assume that the controller is operating normally C. ... of the problem D. feel the outside of the casing with your hand to see if it is hot

Last Answer : Answer: C

Overheating of relay contacts or contact born out is due to (a) slow making and breaking of load circuit contacts (b) foreign matter on the contact surface (c) too low contact pressure (d) all of the above

Description : Overheating of relay contacts or contact born out is due to (a) slow making and breaking of load circuit contacts (b) foreign matter on the contact surface (c) too low contact pressure (d) all of the above

Last Answer : (d) all of the above

If a magnetic controller contact fails to pick up when the operating coil is energized, one possible cause may be _______________. A. low spring pressure B. low voltage to the coil C. the residual magnetism of the contact faces D. dirty contact faces

Description : If a magnetic controller contact fails to pick up when the operating coil is energized, one possible cause may be _______________. A. low spring pressure B. low voltage to the coil C. the residual magnetism of the contact faces D. dirty contact faces

Last Answer : Answer: B

The illustrated motor fails to start and gives a loud hum when the start button is depressed, your first action should be to __________. EL-0007 A. disassemble the motor to fix the centrifical switch so the start windings will be energized B. push the stop button to deenergize the 'M' coil C. reset the thermal overload D. hold the 'M' contactor closed by hand while wearing electrical safety gloves to get motor started

Description : The illustrated motor fails to start and gives a loud hum when the start button is depressed, your first action should be to __________. EL-0007 A. disassemble the motor to fix the centrifical ... D. hold the 'M' contactor closed by hand while wearing electrical safety gloves to get motor started

Last Answer : Answer: B

Low voltage releases as used in some shipboard motor starter and control equipment will have which of the following characteristics? A. They trip circuit contactors when the motor starts to overspeed. B. They require manual resetting upon restoration of normal voltage. C. They use a phase sensitive relay to trip contacts in series with the holding coil of the starter. D. They allow the motor to restart upon restoration of normal voltage.

Description : Low voltage releases as used in some shipboard motor starter and control equipment will have which of the following characteristics? A. They trip circuit contactors when the motor starts to overspeed. B. ... coil of the starter. D. They allow the motor to restart upon restoration of normal voltage.

Last Answer : Answer: D

Overheating of relay contacts or contact born out is due to?

Last Answer : Overheating of relay contacts or contact born out is due to slow making and breaking of load circuit contacts, foreign matter on the contact surface, too low contact pressure.

When troubleshooting a motor controller, all indications are that a relay coil should be energized. If there were no magnetic pull, with rated voltage measured across the coil, the most probable cause would be that the _________________. A. coil is open B. control fuse is open C. auxiliary contact in series with the coil is defective D. relay armature is stuck

Description : When troubleshooting a motor controller, all indications are that a relay coil should be energized. If there were no magnetic pull, with rated voltage measured across the coil, the most probable cause ... open C. auxiliary contact in series with the coil is defective D. relay armature is stuck

Last Answer : Answer: A

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should (a) have low contact resistance (b) be clean and smooth (c) be of sufficient size and proper shape (d) have all above properties

Description : In order that current should flow without causing excessive heating or voltage drop, the relay contacts should (a) have low contact resistance (b) be clean and smooth (c) be of sufficient size and proper shape (d) have all above properties

Last Answer : (d) have all above properties

The winch shown in the illustration will not operate in any speed in the lowering direction and at an abnormal speed in 'first point hoist'. The possible cause is that _______________. EL-0102 A. contactor coil '3M' has many shorted turns B. resistor 'R8-A2' has an open C. contacts '1M' in the power circuit are badly corroded D. master switch contacts 'MS6' have weak springs

Description : The winch shown in the illustration will not operate in any speed in the lowering direction and at an abnormal speed in 'first point hoist'. The possible cause is that _______________. EL-0102 A. ... '1M' in the power circuit are badly corroded D. master switch contacts 'MS6' have weak springs

Last Answer : Answer: B

If deck machinery is expected to be idle for an extended period of time you should____________. A. have electrical safety gloves available in case of electrical shock before running B. perform a 'high pot' test to determine the condition of the insulation C. water wash the motor and controller to remove any salt that may interfere with smooth operation D. check run at regular intervals to inusre correct operation and to renew the internal coating of lubrication

Description : If deck machinery is expected to be idle for an extended period of time you should____________. A. have electrical safety gloves available in case of electrical shock before running B. perform ... run at regular intervals to inusre correct operation and to renew the internal coating of lubrication

Last Answer : Answer: D

DC relay coil or contactor coils must be connected to which side?

Description : DC relay coil or contactor coils must be connected to which side?

Last Answer : Negative side of the DC supply to avoid galvanic effect on the coil, which will corrode the coil.  

In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 6 reads line voltage, while the voltmeter reading between 2 and 6 reads 0 VAC. The problem is __________. EL-0007 A. the control fuse is the wrong amperage not allowing full current to pass through B. the stop switch is open C. an open in the 'M' coil, 'Ma' contact/start switch or overload contacts D. fuse '10a' is blown

Description : In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 6 reads line voltage, while the voltmeter reading between 2 and 6 reads 0 VAC. The problem is __________. EL- ... in the 'M' coil, 'Ma' contact/start switch or overload contacts D. fuse '10a' is blown

Last Answer : Answer: B

Electrical failures in motors are caused by the breakdown of insulation, which may be caused by _____________. A. penetration of moisture B. accumulation of dirt C. overheating D. all of the above

Description : Electrical failures in motors are caused by the breakdown of insulation, which may be caused by _____________. A. penetration of moisture B. accumulation of dirt C. overheating D. all of the above

Last Answer : Answer: D

As shown in the illustration, once the "LV" relay is energized for operation, what contacts must remain closed to maintain the "LV" relay energized when the control lever is moved away from the "off" or "stop" position? A. "DBa" contact. B. Reset contacts. C. Upper set of "LVa" contacts. D. Lower set of "LVa" contacts.

Description : As shown in the illustration, once the "LV" relay is energized for operation, what contacts must remain closed to maintain the "LV" relay energized when the control lever is moved away from the "off" or "stop" ... . B. Reset contacts. C. Upper set of "LVa" contacts. D. Lower set of "LVa" contacts.

Last Answer : Answer: C

As shown in the illustration, which listed action will occur first when push button 'Q' is depressed? EL-0017 A. Contacts 'H-1', 'H-2' and 'H-3' close. B. Contact 'H-4' closes. C. Operating coil 'C' energizes. D. Switch 'R' opens.

Description : As shown in the illustration, which listed action will occur first when push button 'Q' is depressed? EL-0017 A. Contacts 'H-1', 'H-2' and 'H-3' close. B. Contact 'H-4' closes. C. Operating coil 'C' energizes. D. Switch 'R' opens.

Last Answer : Answer: C

If the motor shown in the illustration will not start when 'Q' is depressed, which of the listed components should be checked FIRST? EL-0017 A. Fuses 'F-1' and 'F-2'. B. Operating coil 'C'. C. Contacts 'H-1', 'H-2', and 'H-3'. D. Contact 'H-4'.

Description : If the motor shown in the illustration will not start when 'Q' is depressed, which of the listed components should be checked FIRST? EL-0017 A. Fuses 'F-1' and 'F-2'. B. Operating coil 'C'. C. Contacts 'H-1', 'H-2', and 'H-3'. D. Contact 'H-4'.

Last Answer : Answer: A

Which of the following statements represents the main difference between a relay and a contactor? A. Contactors control current and relays control voltage. B. A relay is series connected and a contactor is parallel connected. C. Contactors can handle heavier loads than relays. D. Contactors are made from silver and relays are made from copper.

Description : Which of the following statements represents the main difference between a relay and a contactor? A. Contactors control current and relays control voltage. B. A relay is series connected and a contactor ... loads than relays. D. Contactors are made from silver and relays are made from copper.

Last Answer : Answer: C

The only point in the steering stand shown in the illustration which needs periodic lubrication is the ______________. EL-0098 A. repeater assembly ball bearings B. steering wheel bearing C. operation selector switch D. course selector pointer

Description : The only point in the steering stand shown in the illustration which needs periodic lubrication is the ______________. EL-0098 A. repeater assembly ball bearings B. steering wheel bearing C. operation selector switch D. course selector pointer

Last Answer : Answer: B

Consider the following statements: [IES 2007] For a journal rotating in a bearing under film lubrication conditions, the frictional resistance is- 1. Proportional to the area of contact 2. Proportional to the viscosity of lubricant 3. Proportional to the speed of rotation 4. Independent of the pressure Which of the statements given above are correct? (a) 1, 2, 3 and 4 (b) 1 and 4 only (c) 2, 3 and 4 only (d) 2 and 3 only

Description : Consider the following statements: [IES 2007] For a journal rotating in a bearing under film lubrication conditions, the frictional resistance is- 1. Proportional to the area of contact 2. Proportional to the viscosity of lubricant 3. ... 4 (b) 1 and 4 only (c) 2, 3 and 4 only (d) 2 and 3 only

Last Answer : (a) 1, 2, 3 and 4

In the illustration shown, coil 'MR' is a ____________. EL-0012 A. running contactor coil B. rupture (blowout) coil C. resistance coil D. reversing coil

Description : In the illustration shown, coil 'MR' is a ____________. EL-0012 A. running contactor coil B. rupture (blowout) coil C. resistance coil D. reversing coil

Last Answer : Answer: A

The contacts operated by the D.C. relay coil shown in the illustration are located in the schematic diagram prints at coordinates ____________. EL-0100 A. '41Y' on this page B. '52M52M' and '52H35M' C. '57R' on this page D. '52N' on page '57R'

Description : The contacts operated by the D.C. relay coil shown in the illustration are located in the schematic diagram prints at coordinates ____________. EL-0100 A. '41Y' on this page B. '52M52M' and '52H35M' C. '57R' on this page D. '52N' on page '57R'

Last Answer : Answer: C

The vertical dotted line connecting the small circular symbols at coordinates '05L', '09L', '13L', '21L', '25L', etc., shown in the illustration, indicate that all _______________. EL-0100 A. contacts are operated by the same relay coil B. screw connections are on terminal board 'TB2' C. wires are grounded at both ends of the line D. wires have a common shield

Description : The vertical dotted line connecting the small circular symbols at coordinates '05L', '09L', '13L', '21L', '25L', etc., shown in the illustration, indicate that all _______________. EL-0100 A. contacts are ... board 'TB2' C. wires are grounded at both ends of the line D. wires have a common shield

Last Answer : Answer: B

Damp armature windings in a D.C. motor may lead to ____________. A. reduced voltage B. reduced current C. increased resistance D. overheating

Description : Damp armature windings in a D.C. motor may lead to ____________. A. reduced voltage B. reduced current C. increased resistance D. overheating

Last Answer : Answer: D

The purpose of a magnetic relay is to _____________. A. open a circuit only in the event of overload B. remotely open and close contacts C. provide overcurrent protection during starting D. relay voltages at increased power

Description : The purpose of a magnetic relay is to _____________. A. open a circuit only in the event of overload B. remotely open and close contacts C. provide overcurrent protection during starting D. relay voltages at increased power

Last Answer : Answer: B

In the illustration, the purpose of part B is to _________. EL-0033 A. increase resistance in series with the contacts as they close to prevent arcing B. create a magnetic field in the steel plates that interacts with the arc to cool and extinguish the arc C. cause the contacts to open in the event of an overload D. provide ventilation to the contact when the breaker is close to rated capacity

Description : In the illustration, the purpose of part B is to _________. EL-0033 A. increase resistance in series with the contacts as they close to prevent arcing B. create a magnetic field in the steel ... event of an overload D. provide ventilation to the contact when the breaker is close to rated capacity

Last Answer : Answer: B

Which of the following statements is true concerning the cleaning of electrical contacts? A. Compressed air should be used to blow out metallic dust. B. Magnetic brushes should be used to remove metallic dust. C. The contact surfaces should be greased to increase contact resistance. D. Delicate parts should be cleaned with a brush and an approved safety solvent.

Description : Which of the following statements is true concerning the cleaning of electrical contacts? A. Compressed air should be used to blow out metallic dust. B. Magnetic brushes should be used to remove ... contact resistance. D. Delicate parts should be cleaned with a brush and an approved safety solvent.

Last Answer : Answer: D

If air gap readings for an electical generating machine have changed significantly from the last reading, you should check _________. A. the bearings B. insulation readings and machine cleanliness C. the prime mover thrust bearing D. the field coil bolts for the proper torque values

Description : If air gap readings for an electical generating machine have changed significantly from the last reading, you should check _________. A. the bearings B. insulation readings and machine cleanliness C. the prime mover thrust bearing D. the field coil bolts for the proper torque values

Last Answer : Answer: A

Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in armature reaction are compensated for by the __________ A. governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Description : Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in ... . governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Last Answer : Answer: B