10+ Lakshya Digital Interview Questions and Answers

A starter is required for I.M to initiate the motor. There are various types of starting methods.

• Starter is required to overcome the initial resistance of the motor.

• Types of starting methods include direct-on-line, star-delta, soft starter, and variable frequency drive.

• Direct-on-line is the simplest and most common method.

• Star-delta is used for larger motors.

• Soft starter and variable frequency drive are used for reducing the starting current and providing smooth acceleration.

Voltage cannot be stepped up to very high values of 1000MW and above due to limitations in insulation and equipment.

• Insulation limitations prevent safe operation at high voltages

• Equipment limitations such as transformer size and cost

• High voltage transmission also results in significant power losses

• Alternatives such as high voltage direct current (HVDC) transmission may be used

• Examples of HVDC transmission include the Itaipu HVDC system in Brazil and Paraguay

• HVDC transmission ...read more

Starting current of induction machine is high due to the absence of back EMF.

• Absence of back EMF during starting

• High rotor impedance at standstill

• High torque requirement at starting

• Voltage drop in supply system

The voltage in an ideal current source series to resistor and capacitor can be found using Ohm's law and the capacitor's reactance.

• Use Ohm's law to find voltage across the resistor

• Calculate the reactance of the capacitor using the formula Xc = 1/(2*pi*f*C)

• Add the voltage across the resistor and capacitor to get the total voltage

• In an ideal current source, the current remains constant regardless of the voltage

• The voltage across the capacitor lags behind the current by 90 degre...read more

If voltage is halved, torque will also be halved.

• Torque is directly proportional to voltage in a DC motor.

• Reducing voltage reduces the magnetic field strength, resulting in less torque.

• This relationship is described by the equation T = kV, where T is torque, V is voltage, and k is a constant.

An integration waveform for DC is a straight line.

• The integration of a constant DC signal results in a linear waveform.

• The slope of the line is proportional to the amplitude of the DC signal.

• The waveform starts at zero and continues indefinitely.

• Example: A 5V DC signal would result in a straight line with a slope of 5.

• The area under the line represents the accumulated value of the signal over time.

A diode is an electronic component that allows current to flow in only one direction. A power amplifier is an electronic device that amplifies the power of a signal.

• Diodes are commonly used in rectifiers, voltage regulators, and signal limiters.

• Power amplifiers are used in audio systems, radio transmitters, and radar systems.

• Diodes have a forward voltage drop and a reverse breakdown voltage.

• Power amplifiers have a high gain and can deliver high power output.

• Both diodes and po...read more

Transistors are three-terminal devices used for amplification and switching, while thyristors are four-layer devices used for power control.

• Transistors have three terminals: emitter, base, and collector, while thyristors have four layers: anode, cathode, gate, and base.

• Transistors are used for amplification and switching in low-power applications, while thyristors are used for power control in high-power applications.

• Transistors can be turned on and off by applying a voltage ...read more

Torque-Speed characteristics and plot graphs

• Torque-Speed characteristics show the relationship between torque and speed of a motor

• The graph is a hyperbolic curve with maximum torque at zero speed

• The slope of the curve represents the motor's ability to accelerate

• The area under the curve represents the motor's work output

• Plotting the torque-speed curve helps in selecting the right motor for an application