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q. a 6 - pole dc armature with 36 slots and 2 coil - slidesslot is to be wave wound double layer. calculate the back pitch front - pitch and
q. define and explain the critical field circuit resistance and critical speed of a dc shunt generator. ans. the occ and r - line for a dc
q. state and briefly explain the various phenomena useful for electromechanical energy conversion in rotating machines. sol. in the rotating
q. for an electromagnetic system show that the energy stored in a magnetic field is equal to the area enclosed bw magnetization curves for open
q. in every electromagnetic conversion device both generator and motor action take place simultaneously. explain.the case the output is mechanical
q. what is meant by dynamically induced emf and statically induced emf? on what factors do these depend? derive eq. for these two emfs. sol.
q. describe the principle of energy conversion. show that the reaction of coupling magnetic field on the electrical or mechanical system is
q. derive the expression of torque developed in closely excited magnetic system. clearly explain then assumption made. sol. double - excited
q. two coils with self inductances 1h and 4h have a mutual inductance of 1h. the rms value of current flowing in the two coils is 4a and 1a
q. why are magnetic field system employed in practical electromechanical energy conversion devices rather than electric field systems?ans.in case
q. give the expression for inductance of a ?n? turn coil wound on a core having length i cross - sectional area a and magnetic
q. the area of the hysteresis loop of a given magnetic material is 50cm2 with the two axes scaled as 1cm 20at and 1cm 50mwb for 50hz frequency
leakage flux the flux that links the coil only partially passes through the core does not link the coil as the moving or rotating device is called
requisites of refractory material or essential requirements of good refractorya. it should be able to withstand high temperature.
thermal spelling the breaking or cracking or peeling off the refractory is known as spelling. a good refractory must show a good resistance to
refractoriness under load rul this represents the resistance of a refractory material to the combined efforts of heat and load. rul is the
refractoriness it indicates the capacity of a material to withstand heat without appreciable deformation or softening under particular operating
permeability the rate of diffusion of molten solid liquid and gases through refractories is called permeability. low permeability is usually more
bulk density this is represented by the weight per unit volume of the refractory of gcm3. this volume includes the volume of the pores space
properties of good refractory material the requirements of refractories for different furnaces and heating places depend on the working conditions.
spelling resistance the breaking or cracking or peeling off the refractory is known as spelling. a good refractory must show a good resistance to
heat capacity heat capacity of furnace depend on1 thermal conductivity 2 specific heat and 3 specific gravity of
porosity the property of the refractory brick is the ratio of its pore volume to the total volume. the refractory material with high porosity is not
q. how can you measure the refractories and refractoriness under load of a refractory material?
q. what are refractorys? how are they classified? give the essential requirements of good