Description : Why a dc series motor has a high starting torque?
asked
Mar 15, 2018
by
anonymous
Answer :
Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of D.C. series motor.
asked
Mar 20, 2018
by
anonymous
Description : Why does induction motor have high starting current?
Answer :
In induction motor , the flux produce is quadrature to the applied voltage. Since when we are going to start motor , there is no flux present inside . So in order to lets say compensate it ... times of current to further increase flux. So that is reason for high starting current in induction motor
asked
Mar 15, 2018
by
anonymous
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.
asked
May 8, 2018
by
anonymous
Answer :
For the same H.P. rating and full load speed, following motor has poor starting torque differentially compounded.
asked
Mar 20, 2018
by
anonymous
Answer :
The ratio of starting torque to full-load torque is least in case of shunt motors.
asked
Mar 20, 2018
by
anonymous
Answer :
Capacitor start motor has high torque in starting
asked
Sep 13, 2017
by
anonymous
Description : Why starter is required for starting an induction motor?
asked
Mar 15, 2018
by
anonymous
Answer :
For starting a D.C. motor a starter is required because it limits the starting current to a safe value.
asked
Mar 20, 2018
by
anonymous
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
asked
Sep 6, 2018
by
anonymous
Description : Explain starting system in diesel electric power plant.
Answer :
Starting system in Diesel Electric Power Plant: It includes Storage battery, compressed air tanks, self-starter etc. The purpose of engine starting system is to rotate the engine initially while ... as Ammeters, Voltmeters, Wattmeters, Thermometers, Pressure gauges, Visible and audible alarm etc.
asked
Sep 8, 2018
by
anonymous
Description : State the functions of following elements: i) Diesel engine system ii) Air intake system iii) Engine exhaust system iv) Engine starting system.
Answer :
i) Diesel engine system:- Four strokes Two strokes ii) Air intake system:- Air intake system is provided to supply air to engine cylinder for fuel combustion. iii) Engine exhaust system ... provided to rotate the engine initially until the firing starts and engine run under its own power.
asked
Sep 7, 2018
by
anonymous
Description : Why is it cheaper to transmit electrical energy at high voltage?
Answer :
Because of the electrical energy was step upped by transformers the transformer have high efficiency than the electric energy is cheaper
asked
Mar 10, 2018
by
anonymous
Description : Why high voltage test is done?
asked
Mar 10, 2018
by
anonymous
Description : Why high voltage can reduce power loss?
Answer :
when voltage has increased due to reduced current flow, thus power loss given by ( I^2R) will be low due to reduced current(I^2) provided that resistance (R) is constant.
asked
Mar 10, 2018
by
anonymous
Description : Why high voltage is used in power transmission?
Answer :
The primary reason that power is transmitted at high voltages is to increase efficiency. ... The lower current that accompanies high voltage transmissionreduces resistance in the conductors aselectricity flows ... This means that thin, light-weight wires can beused in long-distance transmission.
asked
Mar 10, 2018
by
anonymous
Description : Why transmission voltages are high?
Answer :
If current is high then I2R losses will be more .If I2R losses is more then heat generated is more. By heat or increasing temperature resistance will also be increase which will decrease ... voltage we are decreasing current which is advantageous. That's why transmission voltages is high.
asked
Dec 16, 2017
by
anonymous
Answer :
MOSFET provides better efficiency at high frequency and its high speed switching losses are less hence MOSFET is used for high frequency.
asked
Sep 10, 2017
by
anonymous
Description : List different starting methods of three phase synchronous motor. Explain any one of them.
Answer :
Different Starting Methods of Three Phase Synchronous Motor: As synchronous motor is not self starting, different methods of starting are as follows: 1) By using an Induction (Pony) motor 2) ... . The rotor gets pulled into synchronism and starts running at constant speed as a synchronous motor.
asked
May 7, 2020
by
anonymous
Description : In a 741 Op-Amp, there is 20 dB/decade fall-off starting at a relatively low frequency. This is due to the (A) applied load (B) internal compensation (C) impedance of the source (D) power dissipation in the chip
Answer :
In a 741 Op-Amp, there is 20 dB/decade fall-off starting at a relatively low frequency. This is due to the internal compensation
asked
Apr 26, 2018
by
anonymous
Answer :
The starting resistance of a D.C. motor is generally low.
asked
Mar 20, 2018
by
anonymous
Answer :
A direct online starter is used for starting motors up to 5 H.P.
asked
Mar 20, 2018
by
anonymous
Answer :
The starting winding of a single-phase motor is placed in stator.
asked
Mar 20, 2018
by
anonymous
Answer :
If starting winding of a single-phase induction motor is left in the circuit, it will draw excessive current and overheat.
asked
Mar 20, 2018
by
anonymous
Answer :
Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a magnetic relay.
asked
Mar 20, 2018
by
anonymous
Answer :
The value of starting capacitor of a fractional horse power motor will be 300 uF .
asked
Mar 20, 2018
by
anonymous
Answer :
A centrifugal switch is used to disconnect starting winding when motor has picked up about 50 to 70 per cent of rated speed.
asked
Mar 20, 2018
by
anonymous
Answer :
The rotor developed by a single-phase motor at starting is zero.
asked
Mar 20, 2018
by
anonymous
Answer :
In a capacitor start motor, the phase displacement between starting and running winding can be nearly 90°.
asked
Mar 20, 2018
by
anonymous
Description : A synchronous motor can be made self starting by providing?
Answer :
A synchronous motor can be made self-starting by providing damper bar.
asked
Mar 18, 2018
by
anonymous
Description : How is a three phase cage induction motor self starting?
Answer :
Any type of induction motor is self starting. Because the reason for torqe production require two flux displaced by some angle theta.If theta is constant with time then torqe will be constant;if ... torqe also pulsating. In induction motor this angle theta is not pulsating.so it is self starting
asked
Mar 17, 2018
by
anonymous
Description : Is induction motor is self starting?
Answer :
Single phase induction motor is not self starting. Three phase induction motor is self starting.
asked
Mar 17, 2018
by
anonymous
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.
asked
Sep 6, 2018
by
anonymous
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.
asked
Sep 6, 2018
by
anonymous
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.
asked
Sep 6, 2018
by
anonymous
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
asked
Sep 6, 2018
by
anonymous
Description : DC motor gross torque example
Answer :
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asked
Apr 24, 2020
by
anonymous
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.
asked
Apr 30, 2018
by
anonymous
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
asked
Apr 29, 2018
by
anonymous
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
asked
Apr 28, 2018
by
anonymous
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.
asked
Apr 28, 2018
by
anonymous
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
asked
Apr 28, 2018
by
anonymous
Description : The torque produced in wattmeter is proportional to
Answer :
A
asked
Apr 26, 2018
by
anonymous
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.
asked
Mar 26, 2018
by
anonymous
Description : The maximum torque of d.c. motors is limited by?
Answer :
The maximum torque of d.c. motors is limited by commutation.
asked
Mar 26, 2018
by
anonymous
Answer :
In a meggar controlling torque is provided by coil.
asked
Mar 21, 2018
by
anonymous
Answer :
In a portable instrument, the controlling torque is provided by spring.
asked
Mar 21, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
For constant torque drive armature voltage control speed control method is preferred.
asked
Mar 20, 2018
by
anonymous
Answer :
The armature torque of the D.C. shunt motor is proportional to armature current.
asked
Mar 20, 2018
by
anonymous