Electrical Drives and Controls (EDC) solved MCQs

explanation:-belt slip ring im is preferred for the operation of jaw crushers. a high starting is provided by the belt ring im. slip rings are used to add external resistance.

explanation:-the belt conveyors can provide continuous-flow transportation. the amount of material transported on a conveyor system depends upon belt speed, belt width.

explanation:-the reactance starting method is the worst method in an induction motor. it uses the concept of the potential divider. the losses are very high in case of reactance starting method.

explanation:-the induction motor is also known as frequency changer. the stator frequency can be changed using the slip concept. the rotor frequency of im is slip×(stator frequency).

explanation:-cranes are used to carry or lift the heavy loads. the capacity of a crane is expressed in terms of tonnes. 1 tonne is equal to 1000 kg.

explanation:-medium duty crane motor is used to develop high starting torque. they provide the output for a specified interval of time without exceeding a specified temperature.

explanation:-the frequency of the rotor side is low as compared to supply frequency. the rotor frequency is slip×(supply frequency)=.34×70=23.8 hz.

explanation:-the frequency of the stator side is high as compared to the rotor side. the stator frequency is (rotor frequency) ÷ slip = 2÷.04 = 50 hz.

explanation:-during resonance condition xl=xc. the value of the resonant frequency is 1÷√lc=1÷√16=.25 rad/sec. the voltage across the capacitor and inductor becomes equal.

explanation:-using the dynamic equation of motor j×(angular acceleration) = motor torque – load torque: 5×(angular acceleration) = 80-30=50, angular acceleration=10 rad/s2.

explanation:-using the dynamic equation of motor j×(angular acceleration) = motor torque – load torque: .541×(angular acceleration) = 2-10=-8, angular acceleration=-14.78 rad/s2. the load torque is greater than the motor torque. the motor will fail to start.

explanation:-the direction of the single- phase im can be reversed by changing the direction of auxiliary winding or main winding current.the net torque developed in the im is imiasin(Φ).

explanation:-intermittent periodic motor is preferred for overhead traveling cranes.

explanation:-thermography is used to detect heat patterns. it uses an infrared rays camera. this test is used to determine the conditions where electric motors are being used.

explanation:-as the size of the motor increases its speed decreases. the range of size of the motor (kw) for efficiency nearly equals to 90 % is 15-150. the efficiency increases as the size increases.

explanation:-the heat loss can be calculated using the joule law of heating effect. the

explanation:-one british thermal unit is equal to .293 watt. 1 btu/h is the amount of energy requires to increase the temperature of one pound of water by 1℉.

explanation:-overloading can be prevented using over-current protection. it will detect the over-current and interrupt the supply.

explanation:-idmt stands for inverse definite minimum time over-current relay. it has both the characteristics of inverse over- current and definite time over-current relay.

explanation:-the most common cause of motor failure is low resistance. overheating, corrosion can damage the insulation of the windings which leads to low resistance.

explanation:-thd stands for total harmonic distortion. it measures the harmonic distortion in the signal. according to ieee-1992, only 5% of thd is valid.

explanation:-the compensator rating can be calculated using the relation qp.u=√1-

explanation:-voltage ripple factor measures the harmonics on the dc side of the converter. the value of voltage ripple factor is √f.f2-1=45.8 %. the form factor is vr.m.s÷vavg.

explanation:-thd measures the harmonics distortion in the signal. the value of thd is

explanation:-voltage ripple factor measures the harmonics on the dc side of the converter. the value of voltage ripple factor is √f.f2-1. the form factor is vr.m.s÷vavg.