What are the possible reasons for motor to take long acceleration time?

1 Answer

Answer :

Following may the possible reasons for motor to take long acceleration time.

a. Excess loading.

b. May be rewound motor with poor quality of winding conductor having high resistance.

c. Defective squirrel cage rotor.

d. Applied voltage is too low. 

Related questions

Description : Reduced voltage applied to a motor during the starting period will _____________. A. result in decreased acceleration time only B. lower the starting current and increase accelerating time C. cause a greater starting torque D. increase the starting current and pump capacity

Last Answer : Answer: B

Description : You are using a mechanical voltage tester to check the fuses in a three-phase circuit supplying an electric motor. For which of the following reasons must the motor be stopped during the test? A. ... circuit would be indicated by the voltage tester with the circuit energized. D. All of the above.

Last Answer : Answer: B

Description : What could be the reasons if a 3-phase synchronous motor fails to start?

Last Answer : It is usually due to the following reasons a. Voltage may be too low. b. Too much starting load. c. Open circuit in one phase or short circuit. d. Field excitation may be excessive

Description : What are the reasons for harmonics in the motor?

Last Answer : Generally even harmonics are not expected to be present in three phase motors. Triple-n harmonics like 3rd, 9th, 15th etc. are also not expected. The dominant odd harmonics expected are 5th ... harmonic winding faults, short circuits. Hot spots in rotor or stator also may indicate higher harmonics.

Description : What are the reasons for winding temperature high in the motor? 

Last Answer : For motors having class - B insulation the temperature should not be more than 110°C and for motors having class - F insulation the temperature should not be more than 130°C. In case temperature is more, then ... to the motor. 4. Others. a. Excessive number of switching operations. 

Description : What are the reasons for vibration in the motor?  

Last Answer : Vibration could be because of mechanical faults and electrical faults. 1. Mechanical faults. a. Wrong alignment of the motor on foundation. b. Wrong installation. c. Improper fitting ... on the vibration of twice the slip frequency developed due to irregular air gap. 

Description : What are the reasons for unbalanced current in motor? 

Last Answer : a. Loose power cable connection. b. Voltage unbalance. c. Short-circuited turns of coils of winding. 

Description : What are the reasons for high current in motor?

Last Answer : a. High frequency – at 51 Hz current will be 105% of the normal current. b. Low frequency – at 47.8 Hz current will be 102% of the normal current. c. High voltage. d. Under voltage. e. Mechanical over loading. f. Process requirement. 

Description : The velocity, time graph of two bodies A and B travelling along the +x direction are given in the fi gure.(a) Are the bodies moving with uniform acceleration ? (b) Which body is moving with greater acceleration ? Give reasons. -Biology

Last Answer : The acceleration is given by the slope of velocity-time graph. Slope of body-A > Slope of body-B as it forms a greater angle with time axis than body B. Thus, body A moves with higher acceleration

Description : What can be possible reasons for a motor failing to start?

Last Answer : No power , Fuse blown , Overload trip, contactor coil burnt , Contactors contacts bad, control circuit relay faulty, stop switch open circuit and start switch does not operate, hold on contact does not make and motor burnt

Description : What are the possible reasons for not coming of rated speed during start?

Last Answer : In case motor does not come to its rated speed then following could be the probable causes. a. Starting load is too high. b. Broken rotor bars (look for cracks near rings). c. Open primary circuit. d. Voltage is too low. 

Description : Why CT operated over load relay is using for loads of high acceleration time upto 30 seconds? How it getting back?

Last Answer : The saturable current transformers linearly transforms the current upto twice the set current, but above this value the transformer core gets saturated and the secondary current is proportionally less. Thus ... overload. When current reduces the core gets de-saturated, as material design is such. 

Description : The speed of a motor car changes from 18 km/h to 72 km/h in 5 s. Its acceleration is (a) 6 m/s2 (b) 5 m/s2 (c) 4 m/s2 (d) 3 m/s2

Last Answer : Ans:(d)

Description : Boiling range of motor gasoline is an indication of the (A) Case of starting (B) Rate of acceleration (C) Vapour locking tendency (D) All (A), (B) and (C)

Last Answer : (B) Rate of acceleration

Description : Develop power and control diagram for secondary frequency acceleration starter of slip ring induction motor. 

Last Answer : Power and Control Circuit diagram for secondary frequency acceleration starter of slip ring induction motor:

Description : The progressive operation of the contactors marked 'A' provide the winch shown in the illustration with __________. EL-0102 A. accumulation B. dynamic braking C. acceleration D. regenerative braking

Last Answer : Answer: C

Description : Across-the-line starters are used with AC motors to provide _____________. A. reduced starting current B. regulated starting current C. high starting torque D. controlled starting acceleration

Last Answer : Answer: C

Description : Discuss the effect of acceleration factor in load flow study.

Last Answer : The acceleration factor is a real quantity and it modify the magnitude of voltage alone.

Description : In Gauss Seidel method the following factors are influenced for operation a) Acceleration factor b) Selection of slack buss c) Both d) None

Last Answer : Ans: Selection of slack buss*

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

Description : The air gap in an induction motor should be periodically checked with a feeler gage to prevent possible ___________. A. rotor contact with the stator B. axial misalignment of the rotor C. damage to the motor bearings D. electrical damage to the bearings

Last Answer : Answer: A

Description : A useful instrument for checking A.C. motor performance by measuring possible unbalanced currents is the _____________. A. hand or battery-operated megger B. vibrating-reed frequency meter C. hook-on voltmeter-ammeter D. D'Arsonval iron-vane probe

Last Answer : Answer: C

Description : An important factor in reducing D.C. motor commutator wear is _______________. A. keeping the ambient humidity as low as possible B. ensuring a very low brush current density C. establishing the copper oxide surface film D. all of the above

Last Answer : Answer: C

Description : Which of the listed precautions should be taken when cleaning the internals of a motor with compressed air? A. Open the machine on both ends so as to allow the air and dust to escape. B. Be certain that the ... panel. C. Be certain that the air is clean and as dry as possible. D. All of the above.

Last Answer : Answer: D

Description : Why the air gap of an induction motor is made as small as possible?

Last Answer : The mmf and the magnetizing current are primarily decided by length of air gap. If air gap is small then mmf and magnetizing current will be low, which in turn increase the value of power factor. Hence by keeping small air gap, high power factor is achieved.

Description : Which of the following actions must be carried out before a voltage tester can be used to test the three line fuses to a three-phase motor? A. The fuses must be removed from the circuit. B. The ... disconnected and tagged. D. Nothing need be done as long as the motor is running under a light load.

Last Answer : Answer: B

Description : A fuse will blow for all the listed reasons EXCEPT ________. A. excessive vibration B. extremely hot surroundings C. loose fuse clips D. low contact resistance within the fuse

Last Answer : Answer: D

Description : What can be the reasons for the failure of the transformer?

Last Answer : Answer: Transformer is one of the most expensive equipments in the Power System. Failure of the transformer can cause outage of power supply for even days. However, multiple things can go wrong with ... relays. 3.Short Circuits 4.Open Circuits 5.Earth Faults 6.Over Voltage 7.Reduced system frequency

Description : What are the reasons for Oil degradation?

Last Answer : 1.Degradation 2.Oxidation 3.Contamination a) Dielectric breakdown voltage indicates the presence of electrically conductive contaminants in oil. b) Interfacial tension and acid number (sometimes called ... c) Water content is temperature dependent. d) Power factor is also temperature dependent.

Description : What are the reasons for abnormal sound or noise?

Last Answer : Motors in general should run very quietly and no abnormal noise is desired. However if noise is there, it could be because of following reasons. a. Windage noise - the noise due to ... For permissible limits of noise levels for rotating electrical machines IS: 12065:1987 is being reffered. 

Description : What are the reasons for bearing temperature high? 

Last Answer : Temperature of bearing should not be more than 90°C. In case temperature is higher than the 90°C the following could be the possible reasons. a. Inadequate lubricants inside the bearing. b. Faulty bearing. c. Bearing is jammed. d. Over greasing. e. Improper grade of lubricant.