Utilization of Electrical Energy

What do you mean by electrical energy? Explain the different class of electrical consumers and their demand.

Elaborate the role of electrical energy in the sustainable development of the country. Describe on the basis of the utilization of the electrical energy.

Discuss the role of electrical energy in modern society?

A horizontal conveyer belt moving at a uniform speed of 2.2 m/s transports material at the rate of 200 tones/hour. Belt is 100 m long and driven by a motor at 1500 rpm. (i) Determine load inertia referred to motor shaft. (ii) Calculate torque that motor should develop to accelerate the belt from standstill to fill speed in 8 second. Moment of inertia of motor is 0.1 kg-m².

For the selection of various types of motor, what are the classes duties to be performed by the motor on the basis of load variations? List out some examples of the driver/machine applicable to various classes of duties.

A motor is used to drive a hoist. Motor characteristics are given by: Quadrants I, II and IV: T = 200-0.2N, N-m; Quadrants II, III and IV: T = -200-0.2N, N-m. Where N is the speed in rpm. When hoist is loaded, the net load torque T1 = 100, N-m and when it is unloaded, net load torque T1 = -80, N-m. Obtain the equilibrium speeds for operation in all the four quadrants.

Explain Ward-Leonard System of speed control with diagram. Also state the advantages and disadvantages of this method.

A single phase 220V, 50Hz supply feeds a separately excited dc motor through two single phase semi converters, one for the field and another for armature. The firing angle of the field semi converters is zero, the field resistance is 250 Ω and the armature resistance is 0.2 Ω. The load torque is 150 Nm at 1500 rpm. The voltage constant is 0.8 V/A rad/s and torque constant is 0.8 Nm/A². Assuming armature and field current to be continuous and neglecting losses, determine: (i) Field current. (ii) Firing of the converter in the armature circuit. (iii) Power factor of the converter of the armature circuit.

A single phase, 220 V, 50 Hz supply feeds a separately excited dc motor through two single phase semi-converters, one for the field and another for armature. The firing angle for the field semi-converter is zero. The field resistance is 250 Ω and armature resistance is 0.2 Ω. The load torque is 50 N-m at 1000 rpm. The voltage constant is 0.8 V/A-rad/s and the torque constant is 0.8 N/A². Assuming the armature and field currents to be continuous and neglecting losses, Determine: (i) Field current. (ii) Firing angle of the converter in the armature circuit. (iii) Power factor of the converter of armature.

A DC chopper fed from 400V supply runs a separately excited motor. The armature resistance Ra = 0.1 Ω. The motor voltage constant is 4 Vsec/radian, the average armature current Ia = 150 A. the armature current is continuous and has negligible ripple. Determine (a) The input power (b) The motor speed and (c) The developed torque for a duty cycle of 60%. Neglect the losses in chopper. If the duty cycle of chopper varies between 10% and 90%, find maximum and minimum speed.

A 3 phase fully controlled Thyristor Bridge with 400 V, 3 phase, 50 Hz supply is feeding a separately excited DC motor. Armature resistance is 0.2 Ω, armature rated current is 100 A and back emf constant is 0.25 V/rpm. Determine no-load speed if no-load armature current is 5 A and firing angle is 45°. Also determine firing angle to obtain a speed of 1500 rpm at rated current.

Draw the torque speed-characteristics of induction motor with constant V/f control for speed variation from very low up to the base speed. Describe an open loop control scheme for induction motor with constant V/f control.

A 400 V 4 pole 50 Hz3 phase star connected induction motor has the following parameters: number of stator turns/phase is twice the number of rotor turns/phase. R₁ = 0.64 Ω, X₁ = 1.1 Ω, R₂ = 0.8 Ω, X₂ = 0.12 Ω. The load torque is proportional to the square of speed and is 40N-m, at 1440 rpm. If the motor speed is 1300 rpm, find (a) load torque (b) rotor current (c) stator applied voltage. Neglect no load current.

What is self contained electric vehicle? What are the transmission systems employed in these types of electric vehicle? Explain.

A train runs between two stations 2 KM apart at an average speed of 40 km/h. The run is to be made according to simplified quadrilateral speed time curve. If the maximum speed is to be limited to 60 km/hr, acceleration to 2 km/hr/sec, Coasting retardation to 0.15 km/hr/sec and braking retardation to 3 km/hr/sec. Determine the duration of acceleration, coasting and braking periods.

What type of train service correspond to trapezoidal and quadrilateral speed time curve?

What is demand side management? Explain the effective techniques for effective demand side management.

An industry consumes 50000 units of electricity in a year at average power factor of 0.7 lag. The recorded max. demand is 400 kVA. The tariff is Rs. 120/kVA plus Rs. 5.50 per kWhr. Calculate the annual cost of supply and find out annual saving in cost by installing power factor improving device costing Rs. 1000 per kVAR which raises the power factor from 0.7 to 0.9 lagging. Allow 10% per year on the cost of the improving device to cover all additional cost.

A 35 kW induction motor has pf 0.9 and efficiency 0.9 at full load, pf 0.6 and efficiency 0.7 at half load. At no load, the current is 25% of full load current and pf 0.1. Capacitors are supplied to make the line pf 0.8 at half load. With these capacitors in circuit, find the line pf at (i) full load (ii) no load.

A 340 kW, 50Hz, 3 phase star connected induction motor has full load efficiency of 85% and p.f of 0.8 lagging. It is desired to improve the power factor to 0.96 lagging by using bank of three capacitors. Calculate: (i) The kVAR rating of the capacitor bank. (ii) The capacitance of each limbs of the condenser bank connected in delta. (iii) The capacitance of each capacitor, if each one of the limb of the delta-connected condenser bank is formed by using 6 similar 3300v capacitors.