Increasing current means increasing frequency of the motor because current is directly proportional to rotations of the motor rotor

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Jun 1, 2019
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prasadnani

95 views

**Description :** How can we increase the induced current?

**Last Answer :** Induced current can be increased by reducing no of windings on the secondary part compared to primary.

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**Description :** Why does increase in current mean a decrease in voltage?

**Last Answer :** This is because current flows from high potential to low potential to bring the two diffrent potential to unity , thus a reduced potential (voltage)

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**Last Answer :** The size of a synchronous motor decreases with the increase in flux density.

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**Description :** A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

**Last Answer :** A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm

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**Last Answer :** In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be more than full-load current.

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**Last Answer :** Locked rotor current of a shaded pole motor is slightly more than full load current.

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**Last Answer :** In a synchronous motor, the armature current has large values for high and low excitation.

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**Last Answer :** The armature current of the synchronous motor has large values for low and high excitation.

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**Description :** Why does induction motor have high starting current?

**Last 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

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**Description :** How to Increase Gas Mileage

**Last Answer :** How to Increase Gas Mileage Gasoline is a top priority in the budget of any car owner. You'll be surprised at how much you spend on gasoline in between refills, especially if you drive every day. With ... , but also save big money on trips to the fuel pump and refills for your car's fuel tank.

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**Description :** How to Increase Fiber in Your Diet ?

**Last Answer :** How to Increase Fiber in Your Diet Increasing fiber in your diet has many health benefits. Fiber is shown to lower cholesterol levels, lower the chances of getting type 2 diabetes, decrease the possibility ... of eight to ten glasses of water daily. The water helps your body digest the fiber faster.

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**Description :** Reduction in core losses and increase in permeability are obtained with transformer employing?

**Last Answer :** Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.

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**Description :** For given applied voltage, with the increase in frequency of the applied voltage?

**Last Answer :** For given applied voltage, with the increase in frequency of the applied voltage eddy current loss will remain unchanged.

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**Description :** What are three ways you can increase the strength of an electromagnet?

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**Last Answer :** The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.

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**Last Answer :** The current drawn by the armature of D.C. motor is directly proportional to the torque required.

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**Last Answer :** In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to 25% of the previous value.

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**Last Answer :** The direction of rotation of universal motor can be reversed the by reversing the flow of current through either armature winding or field winding.

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**Description :** The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents

**Last Answer :** The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only

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**Description :** Split phase induction motor

**Last Answer :** Split phase induction motor : There are two windings used in split phase induction motor. It is a type of single-phase induction motor. There are two winding one is called main winding and ... motor have low starting torque it is used for small fans, blowers, centrifugal pumps, grinders etc.

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**Description :** Describe the reason of using dc series motor for electric trains.

**Last Answer :** Electric trains require an inverse torque speed characteristics for proper operation. That is a higher torque is required at start (when speed is nil or low) and as the train picks up ... torque - speed characteristics of DC series motors match, these motors are suitable for electric trains

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**Description :** A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be

**Last Answer :** A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

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**Description :** Damper winding in a synchronous motor

**Last Answer :** Damper winding in a synchronous motor Serves to start the motor.

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**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 ... the outer high resistance winding. (D) Large current flows through the inner low resistance winding.

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

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**Description :** A change of 4% in the supply voltage to an induction motor will produce a change of approximately

**Last Answer :** A change of 4% in the supply voltage to an induction motor will produce a change of approximately 8% in the rotor torque

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**Description :** In an induction motor if the flux density is reduced to one-half, of its normal value then the torque will (1) reduce to one-half (2) reduce to one-fourth (3) remain unchanged (4) increase four times

**Last Answer :** In an induction motor if the flux density is reduced.to one-half, of its normal value then the torque will reduce to one-fourth

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**Description :** The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque (1) Decreases (2) Increases (3) Remains constant (4) None of the above

**Last Answer :** The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases

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**Description :** The number of poles of 8/6 stepper motor can be :

**Last Answer :** The number of poles of 8/6 stepper motor can be : 4

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**Description :** In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :

**Last Answer :** In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075

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**Description :** For using regenerative breaking, the most suitable motor is : (A) DC series motor (B) Slip ring induction motor (C) Squirrel cage induction motor (D) Synchronous motor

**Last Answer :** For using regenerative breaking, the most suitable motor is : Slip ring induction motor

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**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

**Last 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

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**Description :** The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is

**Last Answer :** The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 4 percent

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A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for

**Description :** A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for

**Last Answer :** A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for 4 poles

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**Description :** The function of a brush and commutator arrangement in a dc motor is to (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking

**Last Answer :** The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque

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**Description :** The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min (A) 100 rpm (B) 200 rpm (C) 400 rpm (D) 800 rpm

**Last Answer :** The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min 200 rpm

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**Description :** In a split-phase induction motor, the resistance/reactance ratios of windings are such that (A) current in the auxiliary winding leads the current in the main winding (B) current in the ... (C) both windings develop the same starting torque (D) both windings develop high starting current

**Last Answer :** In a split-phase induction motor, the resistance/reactance ratios of windings are such that current in the auxiliary winding leads the current in the main winding

96 views

**Description :** In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then (A) the flux is constant (B) the flux first decreases and then increases in ... increases and decreases in the opposite direction with the same magnitude (D) current flows through the rotor

**Last Answer :** In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then the flux first decreases and then increases in the same direction

100 views

**Description :** The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and quadrature-axis reactance, 0.5 pu, and input voltage, 1.0 pu is (A) 0.25 pu (B) 0.5 pu (C) 1.0 pu (D) 1.5 pu

**Last Answer :** The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and quadrature-axis reactance, 0.5 pu, and input voltage, 1.0 pu is 0.5 pu

582 views

**Description :** The effect of increasing load on a synchronous motor running with normal excitation is (A) Increase both its Ia and power factor. (B) Decrease Ia, but increase power factor. (C) Increase Ia, but decrease power factor (D) Decrease both Ia and power factor.

**Last Answer :** The effect of increasing load on a synchronous motor running with normal excitation is Increase Ia, but decrease power factor

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**Description :** A 3-phase, 4-pole, 50Hz induction motor runs at a speed of 1440 rpm. The rotating field produced by the rotor rotates at a speed of ________ rpm with respect to stator field. (A) 1500 (B) 0 (C) 1440 (D) 60

**Last Answer :** 0

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**Description :** An 8-pole, 50Hz, three-phase induction motor is running at 705rpm and has a rotor copper loss of 5kW. Its rotor input is (A) 5.06 kW (B) 0.3 kW (C) 100 kW (D) 83.33 kW

**Last Answer :** An 8-pole, 50Hz, three-phase induction motor is running at 705rpm and has a rotor copper loss of 5kW. Its rotor input is 83.33 kW

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**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

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

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**Description :** In a 3-phase slip-ring induction motor, the slip at some speed is 0.05. The speed is reduced by inserting an external resistance in the rotor circuit and the slip is 0.15. If the rotor winding resistance per phase is 0.2 Ω, the external resistance is (A) 0.2 Ω (B) 0.3 Ω (C) 0.4 Ω (D) 0.5 Ω

**Last Answer :** In a 3-phase slip-ring induction motor, the slip at some speed is 0.05. The speed is reduced by inserting an external resistance in the rotor circuit and the slip is 0.15. If the rotor winding resistance per phase is 0.2 Ω, the external resistance is 0.3 Ω

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**Description :** A three-phase synchronous motor connected to ac mains is running at full load and unity power factor. lf its shaft load is reduced by half and field current is held constant then its new power factor will be

**Last Answer :** Leading

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**Last Answer :** In variable speed motor a weaker commutating field is needed at low speed than at high speed.

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**Last Answer :** If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor.

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**Last Answer :** For a D.C. shunt motor if the excitation is changed torque will change but power will remain constant.

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**Description :** The speed of a D.C. motor can be controlled by varying 1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above

**Last Answer :** The speed of a D.C. motor can be controlled by varying 1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above

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**Last Answer :** At the instant of starting when a D.C. motor is put on supply, it behaves like a low resistance circuit.

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