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In a portable instrument, the controlling torque is provided by spring.

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Description :

Describe spring control method of producing controlling torque in measuring instrument. Write any two properties required for spring material.

Answer :

A)Spring control method: As shown in the figure, the inner ends of the both springs are attahced to the spindle, while outer end of upper spring is attached to the lever and outer ... of spring material: 1.Non Magnetic material 2.Low specific resistance 3.Low temperature coefficient of resistance

Description :

State the function of controlling torque in electrical measuring instrument.

Answer :

Function of controlling torque  1. The function is to opposes the deflection force and increases with the increase in the deflection of the moving system, to limit its movement. 2. and brought ... set a position where the two opposing forces i.e. deflection and controlling forces are equal. 

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Answer :

In a meggar controlling torque is provided by coil.

Description :

State the function of controlling torque. Write two types of it.

Answer :

Function of Controlling Torque:  To restrict the motion of pointer / spindle and stop the pointer at the relevant position to get correct reading.  To bring back pointer to zero ... measurement is removed.  Types of Controlling Torque: 1. Spring control method 2.Gravity control method 

Description :

Name the different torque and their function in measuring instrument.

Answer :

List of torques in analog instruments:  1. Deflecting torque  2. Controlling / restraining torque.  3. Damping torque.  1. Deflecting torque:  - To create deflection of pointer ... .  - Bring the pointer to standstill quickly.  - To minimize oscillations about final position. 

Description :

In a portable instrument, the controlling torque is provided by  A) Spring B) gravity C) eddy currents D) all of the above

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Answer :

The electric motor used in portable drills is universal motor.

Description :

In a PMMC instrument, the damping provided is :  (A) air damping (C) eddy current damping (B) fluid damping (D) magnetic damping using a magnet

Answer :

In a PMMC instrument, the damping provided is : eddy current damping 

Description :

Answer :

A moving-coil permanent-magnet instrument can be used as ammeter by using a low resistance shunt.

Description :

The meter which does not have any component in it to provide control torque is (A) Electrodynamometer for current measurement (B) Electrodynamometer for voltage measurement (C) Electrodynamometer for power measurement. (D) Electrodynamometer for power factor measurement.

Answer :

The meter which does not have any component in it to provide control torque is Electrodynamometer for power factor measurement.

Description :

The torque produced in wattmeter is proportional to

Answer :

A

Description :

The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are  A) Perpendicular B) Parallel C) Inclined at 60" D) Inclined at 30°

Answer :

The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are Parallel 

Description :

Ideally, the damping torque should be  (1) Proportional to velocity of the moving system and operating current.  (2) Proportional to the velocity of the moving system but independent of operating current.  (3) Independent of the velocity of the moving system and proportional to the operating current.  (4) Independent of the velocity of the moving system and operating current.

Answer :

Ideally, the damping torque should be Proportional to the velocity of the moving system but independent of operating current. 

Description :

A Pyrheliometer is an instrument to measure :  (A) temperature of solar photovoltaic cell  (B) intensity of direct solar radiation at normal incidence  (C) intensity of indirect solar radiation  (D) efficiency of a solar photovoltaic cell

Answer :

A Pyrheliometer is an instrument to measure : intensity of direct solar radiation at normal incidence 

Description :

A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an ammeter with full scale deflection of 100 mA, the required shunt resistance is (A) 1 Ω (B) 1.001 Ω (C) 0.5 Ω (D) 10 Ω

Answer :

A PMMC instrument has FSD of 100 μA and a coil resistance of 1 kΩ. To convert the instrument into an ammeter with full scale deflection of 100 mA, the required shunt resistance is 1.001 Ω

Description :

Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type wattmeter (C) Moving-iron voltmeter (D) Moving-iron wattmeter

Answer :

Identify the instrument that does not exist (A) Dynamo-meter type ammeter (B) Dynamo-meter type wattmeter (C) Moving-iron voltmeter (D) Moving-iron wattmeter

Description :

Answer :

A multirange instrument has multiple shunt or series resistances inside the meter.

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Answer :

The scale of a rectifier instrument is linear.

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Answer :

A moving iron instrument can be used for both D.C. and A.C.

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Answer :

A moving-coil permanent-magnet instrument can be used as flux-meter by eliminating the control springs.

Description :

What is the definition of a primary instrument?

Description :

Eddy current damping cannot be used for moving iron instrument because

Answer :

Eddy current damping cannot be used for moving iron instrument because the presence of a permanent magnet required for such purpose would affect the deflection and hence the reading of the instrument

Description :

Answer :

Instrument transformers are potential transformers, current transformers.

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Answer :

The rectifier instrument is not free from frequency error.

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Answer :

The gravity controlled instrument has crowded scale because current is proportional to sine of deflection angle.

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Answer :

If an instrument has cramped scale for larger values, then it follows logarithmic law.

Description :

The ratio of maximum displacement deviation to full scale deviation of the instrument is called?

Answer :

The ratio of maximum displacement deviation to full scale deviation of the instrument is called linearity.

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Answer :

The disc of an instrument using eddy current damping should be of conducting and non-magnetic material.

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Answer :

The pointer of an indicating instrument should be very light.

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Answer :

Meggar is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another.

Description :

Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be

Answer :

Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be 25 N -m

Description :

Answer :

Torque developed by a D.C. motor depends upon magnetic field, active length of the conductor, current flow through the conductors, number of conductors, radius of armature.

Description :

The torque developed by any 3-phase induction motor at 0.8 p.u. slip is (A) Full-load torque (B) unstable torque (C) starting torque (D) break down

Answer :

The torque developed by any 3-phase induction motor at 0.8 p.u. slip is unstable torque

Description :

The maximum torque of d.c. motors is limited by?

Answer :

The maximum torque of d.c. motors is limited by commutation.

Description :

In a double squirrel cage induction motor, good starting torque is produced as (A) Large current flows through the outer high resistance winding. (B) Large current flows through the inner high resistance winding. (C) Small current flows through the outer high resistance winding. (D) Large current flows through the inner low resistance winding.

Answer :

In a double squirrel cage induction motor, good starting torque is produced as Large current flows through the outer high resistance winding.

Description :

Answer :

The ratio of starting torque to full-load torque is least in case of shunt motors.

Description :

Answer :

In repulsion motor, maximum torque is developed when brush axis is at 45° electrical to the field axis.

Description :

Answer :

The torque produced in induction type relay (shaded pole structure) is inversely proportional to the square of the current.

Description :

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

Answer :

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

Description :

The shaft torque of a d.c. motor is less than its armature torque because of .......... losses.

Answer :

The shaft torque of a d.c. motor is less than its armature torque because of rotational losses.

Description :

Answer :

Speed torque characteristic of a repulsion induction motor is similar to that of a D.C. compound motor.

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Answer :

A synchronous motor can develop synchronous torque at synchronous speed.

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?

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.

Description :

The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as?

Description :

Why a dc series motor has a high starting torque?

Description :

DC motor gross torque example

Answer :

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Description :

List the different methods to produce damping torque.

Answer :

Methods of providing damping torque in indicating type instruments: 1) Air friction damping. 2) Fluid friction damping. 3) Eddy current damping.

Description :

Torque angle for the synchronous machine is the angle between (A) stator magnetic field and rotor magnetic field (B) stator magnetic field and net magnetic field in the air gap (C) rotor magnetic field and net magnetic field in the air gap (D) excitation voltage and impedance voltage drop

Answer :

Torque angle for the synchronous machine is the angle between rotor magnetic field and net magnetic field in the air gap

Description :

Answer :

For constant torque drive armature voltage control speed control method is preferred.

Description :

Answer :

The armature torque of the D.C. shunt motor is proportional to armature current.

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