What is DC Motor ?

What is DC Motor ?
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1 Answer

Answer :

: An electric motor that receives electricity from a DC power source is therefore a DC motor.
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Related questions

Selecting a correct DC stepper motor for a project?

Description : Selecting a correct DC stepper motor for a project?

Last Answer : You will need to calculate the moment of inertia of the shaft you are turning so you can determine the required torque. You will get that after you determine the peak acceleration from the velocity ... Once you have acceleration, displacement, and moment of inertia you can size the motor for power.

What battery is recommended with a 3 volt DC motor?

Description : What battery is recommended with a 3 volt DC motor?

Last Answer : Need answer

Why is it dangerous yo supply power to an unloaded series connected dc motor?

Description : Why is it dangerous yo supply power to an unloaded series connected dc motor?

Last Answer : Need answer

If the supply voltage is 220 volts 60 Hz, what is the operating voltage of the motor controller circuitry illustrated? EL-0011 A. 110 volts DC B. 110 volts AC C. 220 volts DC D. 220 volts AC

Description : If the supply voltage is 220 volts 60 Hz, what is the operating voltage of the motor controller circuitry illustrated? EL-0011 A. 110 volts DC B. 110 volts AC C. 220 volts DC D. 220 volts AC

Last Answer : Answer: D

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

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

Which of the listed electrical devices is represented by the symbol shown in the illustration? EL-0055 A. Fixed resistance resistor B. Coil with magnetic core C. DC motor or generator shunt field D. Transformer

Description : Which of the listed electrical devices is represented by the symbol shown in the illustration? EL-0055 A. Fixed resistance resistor B. Coil with magnetic core C. DC motor or generator shunt field D. Transformer

Last Answer : Answer: D

The torque produced by a DC motor armature is the product of the force acting at the armature surface multiplied by _____________. A. work done by the armature in one revolution B. effective armature diameter at which the force acts C. maximum moment arm at the center of rotation of the armature D. perpendicular distance to its center of rotation

Description : The torque produced by a DC motor armature is the product of the force acting at the armature surface multiplied by _____________. A. work done by the armature in one revolution B. effective ... arm at the center of rotation of the armature D. perpendicular distance to its center of rotation

Last Answer : Answer: D

A series wound DC motor has its armature and field connected in series with a resistor. When the motor is disconnected from its power supply, this motor will exemplify __________. A. the proper connections for across the line starting B. the proper connections for an automatic strip heater C. a reversing controller circuit D. dynamic braking

Description : A series wound DC motor has its armature and field connected in series with a resistor. When the motor is disconnected from its power supply, this motor will exemplify __________. A. the ... the proper connections for an automatic strip heater C. a reversing controller circuit D. dynamic braking

Last Answer : Answer: D

If the connections for the field and the armature on a DC motor are reversed, _____________. A. the motor will run as a generator B. the motor will not run C. the direction of rotation will be the same D. the direction of rotation will be reversed

Description : If the connections for the field and the armature on a DC motor are reversed, _____________. A. the motor will run as a generator B. the motor will not run C. the direction of rotation will be the same D. the direction of rotation will be reversed

Last Answer : Answer: C

Which of the listed colors properly describes a DC motor commutator when correct commutation is taking place? A. Shiny blue B. Burnished green C. Brick red D. Chocolate brown

Description : Which of the listed colors properly describes a DC motor commutator when correct commutation is taking place? A. Shiny blue B. Burnished green C. Brick red D. Chocolate brown

Last Answer : Answer: D

If a DC motor runs hot, the cause may be _____________. A. high mica condition B. low ambient temperature C. clogged ventilation ducts D. an open in the shunt field

Description : If a DC motor runs hot, the cause may be _____________. A. high mica condition B. low ambient temperature C. clogged ventilation ducts D. an open in the shunt field

Last Answer : Answer: C

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 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

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

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

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

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

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

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

When an AC or a DC motor fails to start, the FIRST step in troubleshooting should be to check the ____________. A. motor windings for obvious opens B. motor controller leads for continuity C. fuse or circuit breaker D. motor controller leads for grounds

Description : When an AC or a DC motor fails to start, the FIRST step in troubleshooting should be to check the ____________. A. motor windings for obvious opens B. motor controller leads for continuity C. fuse or circuit breaker D. motor controller leads for grounds

Last Answer : Answer: C

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

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

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

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

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

The counter EMF of a DC motor is maximum when the _________. A. motor is at rated speed B. armature is not turning C. motor is almost up to rated speed D. armature has just begun to turn

Description : The counter EMF of a DC motor is maximum when the _________. A. motor is at rated speed B. armature is not turning C. motor is almost up to rated speed D. armature has just begun to turn

Last Answer : Answer: A

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

The counter EMF produced in the windings of a DC motor is 'zero' when the ____________. A. armature has just begun to turn B. armature is not turning C. motor is almost up to rated speed D. motor is at rated speed

Description : The counter EMF produced in the windings of a DC motor is 'zero' when the ____________. A. armature has just begun to turn B. armature is not turning C. motor is almost up to rated speed D. motor is at rated speed

Last Answer : Answer: B

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

When starting a DC propulsion motor the variable rheostat must FIRST be turned ____________. A. all the way to the run position then quickly back to slow B. to the slow position then gradually moved to full speed C. to the mid position D. quickly to the run position

Description : When starting a DC propulsion motor the variable rheostat must FIRST be turned ____________. A. all the way to the run position then quickly back to slow B. to the slow position then gradually moved to full speed C. to the mid position D. quickly to the run position

Last Answer : Answer: B

The item referred to as a pigtail on a DC motor brush rigging is a/an ______________. A. feather spring B. uninsulated wire C. flexible spring adjuster D. brush holder

Description : The item referred to as a pigtail on a DC motor brush rigging is a/an ______________. A. feather spring B. uninsulated wire C. flexible spring adjuster D. brush holder

Last Answer : Answer: B

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

The most common source of excitation for synchronous motors is a/an _____________. A. low voltage battery B. motor attenuator set C. DC exciter generator D. AC supply

Description : The most common source of excitation for synchronous motors is a/an _____________. A. low voltage battery B. motor attenuator set C. DC exciter generator D. AC supply

Last Answer : Answer: C

A synchronous motor maintains synchronism with the rotating field because _____________. A. field strength varies directly with rotor slip B. DC current applied to the rotor coils causes the rotor magnets to lock in with the rotating flux of the stator C. the stator poles are dragged around due to the flux created by the excitation current D. the stator flux rotates in the opposite direction

Description : A synchronous motor maintains synchronism with the rotating field because _____________. A. field strength varies directly with rotor slip B. DC current applied to the rotor coils causes the rotor ... the flux created by the excitation current D. the stator flux rotates in the opposite direction

Last Answer : Answer: B

The purpose of a cage rotor winding placed on the rotor of a synchronous motor is to _____________. A. provide excitation to the DC field B. start the machine as an induction motor C. contribute extra torque at synchronous speed D. prevent the machine from falling out of step

Description : The purpose of a cage rotor winding placed on the rotor of a synchronous motor is to _____________. A. provide excitation to the DC field B. start the machine as an induction motor C. contribute extra torque at synchronous speed D. prevent the machine from falling out of step

Last Answer : Answer: B

Which of the following statements represents an application of a silicon controlled rectifier? A. To provide DC power for a main propulsion motor. B. For use as a voltage reference diode. C. For sensing flame in an automated burner. D. To eliminate power supply hum.

Description : Which of the following statements represents an application of a silicon controlled rectifier? A. To provide DC power for a main propulsion motor. B. For use as a voltage reference diode. C. For sensing flame in an automated burner. D. To eliminate power supply hum.

Last Answer : Answer: A

In a diesel electric plant, raising the generator's field excitation will cause the DC propulsion motor to ________. A. increase in speed B. decrease in speed C. affect generator speed only D. affect main motor speed if done in conjunction with higher generator engine speeds

Description : In a diesel electric plant, raising the generator's field excitation will cause the DC propulsion motor to ________. A. increase in speed B. decrease in speed C. affect generator speed only D. affect main motor speed if done in conjunction with higher generator engine speeds

Last Answer : Answer: A

On some diesel-electric ships, the DC propulsion motor will only attain half speed when the generator fields are fully excited. Speeds above this are obtained by _____________. A. rotating brush alignment B. raising the generator engine speed C. lowering the generator engine speed D. decreasing excitation

Description : On some diesel-electric ships, the DC propulsion motor will only attain half speed when the generator fields are fully excited. Speeds above this are obtained by _____________. A. rotating brush ... B. raising the generator engine speed C. lowering the generator engine speed D. decreasing excitation

Last Answer : Answer: B

Why is the starting current high in a DC motor?

Description : Why is the starting current high in a DC motor?

Last Answer : Answer: In DC motors, Voltage equation is V=Eb-IaRa (V = Terminal voltage, Eb = Back emf in Motor, Ia = Armature current, Ra = Armature resistance).At starting, Eb is zero. Therefore, V=IaRa, Ia = V/Ra, where Ra is very less value and Ia becomes very high.

Why Speed Control of Induction Motor is difficult compared to DC shunt motor?

Description : Why Speed Control of Induction Motor is difficult compared to DC shunt motor?

Last Answer : Answer: Speed Control of DC shunt motor can be possible by providing resistance in the armature and field circuits and varying the resistors speed changes can be carried out over a wide range. ... employed. Care should be taken that in the process efficiency and power factor should be maintained.

DC Motor Applications in Industries

Description : DC Motor Applications in Industries

Last Answer : In spite of wide use of ac supply, dc machines have some advantages compared to ac motors and are used in industries for some applications. Some of the applications where dc motors employed ... , conveyers, heavy planers, for shears and punches, for intermittent high torque loads and air compressors

Give two basic speed control scheme of DC shunt motor?

Description : Give two basic speed control scheme of DC shunt motor?

Last Answer : Answer: 1. By using flux control method: in this method a rheostat is connected across the field wdg to control the field current. So by changing the current the flux produced by the field wdg can ... ) can be varied, and since speed is directly proportional to Eb-IaRa the speed can be controlled.

Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor?

Description : Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor?

Last Answer : DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without load.

Which Motor Has High Starting Torque And Staring Current Dc Motor, Induction Motor Or Synchronous Motor?

Description : Which Motor Has High Starting Torque And Staring Current Dc Motor, Induction Motor Or Synchronous Motor?

Last Answer : DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without load.

What is brushless DC motor?

Description : What is brushless DC motor?

Last Answer : An inverter fed trapezoidal permanent magnet AC motor drive operating in self-controlled mode is called brushless dc motor.

What is DC motor?

Description : What is DC motor? 

Last Answer : An electric motor converts electrical energy in to mechanical energy.  

In DC motor what is the relation between speed and field flux?

Description : In DC motor what is the relation between speed and field flux?

Last Answer : Speed of a DC motor is inversely proportional to the field flux.