What is the necessity of shaft voltage measurement?

1 Answer

Answer :

It is to observe insulation of bearing 6 & 7 and hydrogen seal assembly. It requires minimum leakage current (<100mA) through bearings and shaft seals to avoid pitting of bearings.

If the leakage current >100mA, clean the insulation provided between bearing pedestal and seal housing with earth. 


Related questions

Description : What is the necessity for predetermination of voltage regulation?

Last Answer : Most of the Alternators are manufactured with large power rating , hundreds of kW or MW, and also with large voltage rating upto 33kV. For Alternators of such power and voltage ratings ... performance like voltage regulation then can be predetermined at any desired load currents and power factors.

Description : Draw a neat sketch of a hollow propeller shaft. Label all the parts. State the necessity of Universal joint.

Last Answer : Necessity of universal joint: ● A universal joint is used where two shafts are connected at an angle to transmit the torque. ● Universal joint is used to transmit motion at varying angles.

Description : State the necessity of providing tunnel shaft.

Last Answer : Necessity of providing tunnel shaft1) To provide opening for removal of muck. 2) To expedite the construction work of the tunnel by starting excavation at several points at the same time. 3) To ... out the water from the tunnel. 4) To provide natural ventilation during construction of the Tunnel.

Description : The twisting force developed by a motor and applied to a shaft is called _____________. A. magnetism B. electromotive force C. torque D. voltage

Last Answer : Answer: C

Description : The conversion of the throttle command voltage to the signal necessary to achieve the desired shaft RPM is accomplished by the _____________. A. ahead or astern function generator of the ... circuit C. operational amplifiers in the autorotation circuit D. long time constant amplifier circuit

Last Answer : Answer: A

Description : The torque produced by a motor when its shaft will not turn, even though rated voltage is applied to the stator, is known as _____________. A. locked-rotor torque B. pullout torque C. breakdown torque D. torque margin

Last Answer : Answer: A

Description : How shaft voltage produced by turbine? 

Last Answer : Due to un-symmetry in the flux path of core, non-uniform air gap, un-symmetry in the rotor magnetic field during short circuit in the rotor winding, causes voltage to develop across the ends of rotor shaft. 

Description : What is the Necessity of Starter of an Induction Motor?

Last Answer : Induction motors, when direct-switched, take five to seven times their full-load current and develop only 1.5 to 2.5 times their full-load torque. This initial excessive current is ... electrical equipment connected to the same lines. Hence, a starter is necessary to overcome this objection.

Description : What is the necessity of starter?

Last Answer : Its function is to reduce starting current and also provide protection against over load and over voltage.

Description : What is the necessity of Seal oil system?

Last Answer : The annular gap between stator and rotor of the generator are to be sealed to prevent hydrogen leak from the casing. Type of seal – ring type shaft seals Pressure of seal oil – 4 kg/cm2

Description : What is the necessity of DC motor starter?

Last Answer : Eb = V - Ia ra. ∴ Ia = V - Eb / ra. At the time of starting from the rest there is no any back emf (Eb) in the armature. So a large current flows through the armature based on ... develops back emf (Eb) which regulates it's speed and armature current. This can be achieved by the help of starter.

Description : According to U. S. Coast Guard Regulations (46 CFR), the motor controller for a submersible electric motor driven bilge pump should be installed _____________. A. in the shaft alley B. at the submersible bilge pump C. above the uppermost continuous deck D. at the engine room emergency control panel

Last Answer : Answer: C

Description : To protect the rotor of a motor disassembled for maintenance or overhaul, it should be ___________________. A. suspended by wire slings in one corner of the shop B. stowed upright on its shaft C. supported by two 'V' notched wood blocks D. returned to the frame as soon as the bearings are removed

Last Answer : Answer: C

Description : Which of the listed conditions will occur if dirt and grease are allowed to accumulate between the commutator segments of a motor? A. A partial short circuit. B. A dead short circuit. C. Misalignment of the motor shaft. D. Overspeeding of the motor.

Last Answer : Answer: A

Description : On electrical generators one of the bearings is isolated from the bedplate. This insulating block should not be painted and must be kept clean to ___________. A. protect operating personnel from shock ... the prime mover as it warms up D. eliminate shaft currents to prevent damaging the bearings

Last Answer : Answer: D

Description : The reactive power drawn by a motor from an AC generator is the power which is _____________. A. used to establish the magnetic field of the motor B. lost in overcoming friction in the ... by current flow through the windings D. transmitted directly through the rotor shaft to perform useful work

Last Answer : Answer: A

Description : One of the generator bearing shells is generally insulated from the end housing in order to prevent _____________. A. rapid brush wear B. residual magnetism leak off C. excessive field winding heat D. circulation of shaft currents

Last Answer : Answer: D

Description : One of the generator or motor bearings is generally insulated from the end housing in order to prevent ________. A. rapid brush wear B. current leakage from the shaft C. excessive field winding heat D. circulation of shaft currents induced in the machine's frame

Last Answer : Answer: D

Description : In the illustration, the assembly labeled 2 is a ________. EL-0001 A. wound rotor and shaft for a single phase induction motor B. conduction rotor and shaft for a polyphase induction motor C. ... cage rotor and shaft for a polyphase motor D. squirrel cage rotor for a single phase induction motor

Last Answer : Answer: C

Description : The direction of propeller shaft rotation in a turbo-electric synchronous propulsion drive motor is changed by reversing the _____________. A. polarity of the propulsion motor B. polarity of the propulsion generator C. phase sequence of power to the motor D. phase sequence of power to the generator

Last Answer : Answer: C

Description : The propeller shaft speed in a turbo-electric, synchronous, propulsion drive motor is changed by varying the __________. A. turbine speed B. number of motor poles C. field strength of the generator D. field strength of the motor

Last Answer : Answer: A

Description : When removing ball or roller bearings from the shaft of a motor, you should use a _____________. A. rawhide hammer B. brass mallet C. wheel puller D. soft iron pry bar

Last Answer : Answer: C

Description : A handheld digital tachometer could give a bad reading if ___________________. A. aimed directly at the shaft B. partially aimed at a 60 Hz. fluorescent light C. positioned 5-10 inches from the shaft D. the tape is too shiny

Last Answer : Answer: B

Description : Modern handheld digital tachometers operate by counting light pulses returned to the unit by ______________. A. the tach generator B. either the coupling or shaft C. a small bulb attached to the shaft D. a piece of reflective tape

Last Answer : Answer: D

Description : Which of the following methods should be used to test for an 'open' coil in an AC motor stator? A. Test with an ohmmeter, one test lead on the shaft, and the other test lead to the stator leads ... an open coil. D. Use a growler, listening for noise and vibration to increase when over an open coil.

Last Answer : Answer: B

Description : Electric propulsion coupling excitation is reduced at slow speeds to ___________. A. increase speed control B. increase shaft torque C. prevent coupling overheating D. prevent coupling slippage

Last Answer : Answer: C

Description : What are the effects of broken rotor bars and broken shaft parts?

Last Answer : Broken rotor bars a. High stator current and over heat of stator winding. b. More harmonic currents in end parts. c. High vibration. Broken shaft or parts a. Stator winding loose bracing. b. Rotor high vibration and bearing vibration. c. Frame vibration and more harmonics in side bands. 

Description : What is the purpose of shaft earthing and bearing insulation?

Last Answer : The voltage generated in the shaft due to the leakage fluxes can circulate current through the shaft. If shaft earthing is not done the leakage current will flow through the bearings to ground and pitting of bearings will result. Hence bearing foundation and pipelines are insulated. 

Description : Why shaft-earthing brush is different from normal brush?

Last Answer : The contact resistance should be very low for shaft earthing brush, to prevent even small current through the oil film, so used copper magnite brush or silver carbon brush.

Last Answer : Hi Voltage Of measurement Equipment , ,,,,, 1 / electrostatic Volt Meters 2 / Royal Crotch Voltmeter 3 / Attracted Dix Type Electro Static Voltmeter.

Description : The device used ' for the measurement of current, voltage and resistance is: A. AVO meter B. Galvanometer C. Ammeter D. Ohm meter

Last Answer : ANSWER: A

Description : Instruments of Measure The device used ' for the measurement of current, voltage and resistance is: A. AVO meter B. Galvanometer C. Ammeter D. Ohm meter

Last Answer : ANSWER: A

Description : The device used ' for the measurement of current, voltage and resistance is: A. AVO meter B. Galvanometer C. Ammeter D. Ohm meter

Last Answer : ANSWER: A

Description : The device used ' for the measurement of current, voltage and resistance is: A. AVO meter B. Galvanometer C. Ammeter D. Ohm meter

Last Answer : ANSWER: A

Description : The most common unit of noise measurement in white noise voltage testing. A. NPR B. dBm C. dBW D. dBrn

Last Answer : A. NPR

Description : For dynamic strain measurement, the Wheatstone bridge used is of __________ type. (A) Voltage sensitive null (B) Voltage sensitive deflected (C) Current sensitive deflected (D) None of these

Last Answer : (B) Voltage sensitive deflected

Description : When taking a voltage measurement, which lead of the voltmeter should you connect to the circuit first?

Last Answer : Ground.

Description : On what range should you set the voltmeter prior to taking a voltage measurement?

Last Answer : Highest.

Description : Voltage measurement in a high impedance circuit requires a voltmeter with

Last Answer : high input impedance

Description : Explain the measurement of voltage and frequency using CRO.

Last Answer : Voltage Measurement: CRO displays the voltage signal as a function of time on its screen. The amplitude of that voltage signal is constant, but we can vary the number of divisions that cover the voltage ... /division nv is the number of divisions that cover the signal in vertical direction.

Description : Describe with neat circuit diagram the method of measurement of power in a High voltage, high current a.c circuit.

Last Answer : Circuit diagram:  Explanation:  The primary winding of P.T is connected across high voltage side and secondary winding is connected to pressure coil of low range wattmeter. The high voltage is ... is used Real power consumed = reading of wattmeter x ratio of C.T x ratio of P.T

Description : Weins bridge is used for measurement of frequency in the applied voltage waveform is measurement of frequency in the applied voltage waveform is   (A)sinusoidal (B) square (C) rectangular (D) triangular

Last Answer : Weins bridge is used for measurement of frequency in the applied voltage waveform is measurement of frequency in the applied voltage waveform is sinusoidal 

Description : Electrostatic type instruments are mainly used for measurement of: a) Heavy currents b) Low currents c) Low voltages d) High voltages

Last Answer : Ans: D

Description : When a resistor is used as a shunt and is connected in parallel with a meter movement coil, it will provide _____________. A. a measurement of circuit resistance B. an increased accuracy of approximately 1.5 percent C. an extended meter range D. none of the above

Last Answer : Answer: C

Description : In order to increase its range of measurement, a resistance would be placed in series with which of the following instruments? A. DC voltmeter B. DC ammeter C. frequency meter D. power factor meter

Last Answer : Answer: A

Description : What is meant by tan-delta measurement?

Last Answer : It is the tan of the angle between the capacitive current and the total current.   As the value of tan delta increases the resistive component of the current in increasing. Hence it shows a weak insulation.  

Description : What is the equation for resistance measurement of PT 100 thermocouple? 

Last Answer : °C = (R-100) / 0.39