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Dynamic or rheostatic braking,plugging and regenerative braking

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Description : A DC chopper is used for regenerative braking of a separately excited DC motor. The DC supply voltage is 400V. The armature current during regenerative braking is kept constant at 300 A with negligible ripple. For a duty cycle of 60% ... to the DC supply is  (a) 78 kW (b) 58 kW (c) 38 kW (d) 48 kW

Answer : A DC chopper is used for regenerative braking of a separately excited DC motor. The DC supply voltage is 400V. The armature current during regenerative braking is kept constant at 300 A with negligible ripple. For a duty cycle of 60% the power return to the DC supply is  48 kW

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Answer : Fractional pitch windings are used in DC machines to Reduce sparking

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Answer : The introduction of interpoles in between the main poles improves the performance of DC machines because: a counter emf is induced in the coil undergoing commutation

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Answer : Circuit Operation  1)Starting & Running - Pressing the start button S2 will energise coil C2 provided the stop button S1 is not pressed and the overload OL2 has not tripped. The retaining contact of C2 ... de-energising C3 and removing DC from the stator. This in turn de-energises the timer coil. 

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Description : Explain regenerative braking for D.C. series motor.

Answer : Schematic diagram of regenerative braking of D.C. series :-  Explanation of regenerative braking: During normal running, motors are connected in parallel with field winding in series ... For final stop mechanical braking is applied. External Resistances are connected to limit the current.

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Answer : Shunt motors,  Series motors, Compound motors

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Description : electrical machines used in electro-agro system. 

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Answer : ANSWER: Z -- 80%

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