A synchronous motor starts as usual but fails to develop its full torque. What could it be due to?

A synchronous motor starts as usual but fails to develop its full torque. What could it be due to?
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1 Answer

Answer :

a. Exciter voltage may be too low.
b. Field spool may be reversed
c. There may be either open-circuit or short-circuit in the field.
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Related questions

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

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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

Hunting of a synchronous motor:

Description : Hunting of a synchronous motor:

Last Answer : When the mechanical load is constant, the rotor settles down to an absolutely constant speed with the torque angle fixed by the particular delivered power. When there is a change in load the rotor speed ... are short circuited; copper bars are embedded in the faces of the field poles of the motor.

In what way synchronous motor is different from other motors?

Description : In what way synchronous motor is different from other motors?

Last Answer : All dc and ac motors work on the same principle. Synchronous motor operates due to magnetic locking taking place between stator and rotor magnetic fields.

State the characteristic features of synchronous motor.

Description : State the characteristic features of synchronous motor.

Last Answer : a. the motor is not inherently self starting b. The speed of operation is always in synchronous with the supply frequency irrespective of load conditions c. The motor is capable of operating at any power factor.

Write the applications of synchronous motor.

Description : Write the applications of synchronous motor.

Last Answer : a. Used for power factor improvement in sub-stations and in industries. b. As synchronous condenser c. Used for constant speed applications

What are V and inverted V curves of synchronous motor ?

Description : What are V and inverted V curves of synchronous motor ?

Last Answer : The variation of magnitude of line current with respect to the field current is called V curve . The variation of power factor with respect to the field current is called inverted V curve.

How the synchronous motor can be used as s synchronous condenser?

Description : How the synchronous motor can be used as s synchronous condenser?

Last Answer : Synchronous motor is operated on over excitation so as to draw leading reactive current and power from the supply lines. This compensates the lagging current and power requirement of the load making ... to become unity. The motor does the job of capacitors and hence called as synchronous condenser.

Why a synchronous motor is a constant speed motor?

Description : Why a synchronous motor is a constant speed motor?

Last Answer : When load increase in synchronous motor the load angle δ also increases but speed remains constant. The further increase in load cause further increase in load angle. When load angle reaches ... out of synchronism. Hence the motor rotates at synchronous speed otherwise it comes out of synchronism.

What is the effect on speed if the load is increased on a 3 phase synchronous motor?

Description : What is the effect on speed if the load is increased on a 3 phase synchronous motor?

Last Answer : The speed of operation remains constant from no load to maximum load in the motor operating at constant frequency bus bars.

Why damper windings are used in synchronous motor? Or How synchronous motor is started as squirrel cage motor?

Description : Why damper windings are used in synchronous motor? Or How synchronous motor is started as squirrel cage motor?

Last Answer : The damper winding consists of short circuited copper bars embedded in the the face of the rotor poles. When an ac supply is provided to stator of a 3-phase synchronous motor, stator winding produces ... magnetic field and damper winding is zero. Hence there will be no emf induced in damper winding.

What are the methods of starting synchronous motor?

Description : What are the methods of starting synchronous motor?

Last Answer : 1. Pony motor starting( using ac or dc motor) 2. Starting as squirrel cage Induction motor or using damper winding 3. Starting as slip ring Induction motor or synchronous motor 4. Using dc machine coupled to it.

Why synchronous motor is not self starting?

Description : Why synchronous motor is not self starting?

Last Answer : Synchronous motor is a doubly excited machine i.e two electrical inputs are provided to it. It's stator winding which consists of a 3 phase winding is provided with 3 phase supply and rotor ... due to attractive or repulsive force and remain in standstill condition. Hence it is not self starting.

Distinguish between synchronous phase modifier and synchronous condenser

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Last Answer : A synchronous motor used to change the power factor or power factor in the supply lines is called synchronous phase modifier. A synchronous motor operated at no load with over excitation condition to draw large leading reactive current and power is called a synchronous condenser.

What is synchronous condenser?

Description : What is synchronous condenser?

Last Answer : An over-excited synchronous motor under no load , used for the improvement of power factor is called as synchronous condenser because, like a capacitor it takes a leading current.

What is pull out torque?

Description : What is pull out torque?

Last Answer : The maximum torque developed by the motor without pulling out of synchronism is called pull out torque. Its value varies from 1.5 to 3.5 times full load torque.

What is pull in torque?

Description : What is pull in torque?

Last Answer : The torque which is required to pull the motor into synchronism when it is running as induction motor is called pull in torque.

What is pony motor starting?

Description : What is pony motor starting?

Last Answer : In this method the rotor is made to rotate by some external device called pony motors. Once the rotor attains synchronous speed, the DC excitation to the rotor is switched on. Once synchronism is established the pony motor is decoupled. The synchronous motor continuously runs at synchronous speed.

What is critical excitation?

Description : What is critical excitation?

Last Answer : The excitation for which power factor of the synchronous motor is unity and the back emf is equal to supply voltage.

What is over excitation?

Description : What is over excitation?

Last Answer : The excitation for which power factor of the synchronous motor is leading and the back emf is greater than supply voltage.

What is under excitation?

Description : What is under excitation?

Last Answer : The excitation for which power factor of the synchronous motor is lagging and the back emf is less than supply voltage.

What is normal excitation?

Description : What is normal excitation?

Last Answer : The excitation for which power factor of the synchronous motor is lagging and the back emf is equal to supply voltage.

What are the effects of hunting?

Description : What are the effects of hunting?

Last Answer : Loses synchronism Develops mechanical stress on rotor shaft Increase machine losses Increase temperature of machine

What is hunting?

Description : What is hunting?

Last Answer : The sudden changes of load on synchronous motor set up oscillations in the rotor. Such oscillation of rotor about its new equilibrium position is called hunting.

What is the function of damper winding?

Description : What is the function of damper winding?

Last Answer : To provide starting torque To prevent or minimize hunting

A synchronous motor can develop synchronous torque?

Last Answer : A synchronous motor can develop synchronous torque at synchronous speed.

If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B. starting winding will burn out C. motor will immediately stall under load D. motor torque will be above normal at rated speed

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The function of amortisseur, or damper windings in a synchronous motor is to _____________. A. eliminate slippage B. provide excitation C. provide starting torque D. increase efficiency

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The primary function of an electric motor is to ___________. A. develop torque B. generate high voltages C. produce a magnetic field D. generate high electrical resistance

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If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, the motor will _____________. A. continue to run, but will vibrate and have reduced torque B. speed up due to the reduced number of poles C. run cooler due to reduced current flow D. stop

Description : If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, the motor will _____________. A. continue to run, but will vibrate and have reduced ... speed up due to the reduced number of poles C. run cooler due to reduced current flow D. stop

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If the driving torque, such as that produced by a diesel engine, creates pulsations when coupled with a synchronous generator operating in parallel; the generator rotor may be periodically pulled ahead or behind its normal position as it rotates. This co A. hunting B. direct coupling C. peaking D. harmonic coupling

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If the driving torque, such as that produced by a diesel engine, creates pulsations when coupled with a synchronous generator operating in parallel; the generator rotor may be periodically pulled ahead or behind its normal position as it rotates. This hu A. amortisseur windings B. direct coupling C. increase governor speed droop D. decreasing governor speed droop

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Synchronous Of the motor Generated Torque What? What ?

Last Answer : 1 / Starting Torque 2 / Running Torque 3 / Pool In Torque 4 / Pool Out Torque

Synchronous Of the motor Torque Angle What ?

Last Answer : synchronous Of the motor Rotor Poll Axis And Stator Poll Axis Of In That Angular Interval Stays Him That said Of the motor Torque Angle Says.

The maximum constant load torque under which a synchronous motor will pull into synchronism...

Description : The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as?

Last Answer : The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as pull-in torque.

What is the maximum value of torque angle in synchronous motor?

Description : What is the maximum value of torque angle in synchronous motor?

Last Answer : The maximum value of torque angle in synchronous motor is 90 degrees electrical.

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

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

In the illustration if the compressor fails to start but the condenser fan motor is running the problem is _______. EL-0042 A. no power between L1 and L2 B. the yellow wire is open at the freezer temperature control switch C. the overload is open D. the blue wire from the defrost heater is open

Description : In the illustration if the compressor fails to start but the condenser fan motor is running the problem is _______. EL-0042 A. no power between L1 and L2 B. the yellow wire is open at the freezer temperature control switch C. the overload is open D. the blue wire from the defrost heater is open

Last Answer : Answer: C

In the illustration if the compressor fails to start but the condenser fan motor is running the problem is _______. EL-0043 A. no power between L1 and L2 B. the yellow wire is open at the freezer temperature control switch C. the overload is open D. the blue wire from the defrost heater is open

Description : In the illustration if the compressor fails to start but the condenser fan motor is running the problem is _______. EL-0043 A. no power between L1 and L2 B. the yellow wire is open at the freezer temperature control switch C. the overload is open D. the blue wire from the defrost heater is open

Last Answer : Answer: C

The synchronous motor will develop maximum power when the load angle is?

Description : The synchronous motor will develop maximum power when the load angle is?

Last Answer : The synchronous motor will develop maximum power when the load angle is 900.