Electrical Engineering

Nowadays, domestic fan regulators do not work on potential divider concept and there is no power loss if you operate the fan at lower/higher speeds.

Test before Touch. This is a mantra that every electrical engineer should remember. You need to check that there is no voltage before touching any live part. It may have been fed from a different source.

Electric shock is caused by current and not voltage. 30mA of current is enough to cause ventricular fibrillation in your heart.

Ohm's law V=IR, current is proportional to the voltage applied.

gallon (gal): Imperial gallon. A measure of volume. 1 gal = 4.54596 litre gallon (US) A measure of volume. 1 US gallon = 3.785 litre.

Distortion; In systems that handle electrical signals, distortion is a generally unwanted change in the signal. Not all signal alterations are considered distortion. For instance, a uniform delay or a linear attenuation or amplification would generally not be considered distortion.

damping : Decrease in the amplitude of an oscillation or wave motion with time.

Inductive loads : Loads that produce a magnetic field, often accompanied by heat.

Question No. 1: Define Amplifier. Answer: An electronic device for increasing the amplitude of electrical signals, used chiefly in sound reproduction a device consisting of an amplifier combined with a loudspeaker and used to increase the volume of the sound produced by electric guitars and other musical instruments.   Question No. 2: What is SCR? Answer: Thyristors or silicon controlled rectifiers; SCR are found many uses in electronics, and in particular for power control. These devices have even been called the workhorse of high power electronics.Thyristors are able to switch large levels of power are accordingly they used in a wide variety of different applications. Thyristors even finds uses in low power electronics where they are used in many circuits from light dimmers to power supply over voltage protection.   Question No. 3: What is ZIGBEE? Answer: ZIGBEE is a IEEE 802.15.4 based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios.   Question No. 4: Define various modes of operation of timer. Answer: The 555 has three main operating modes, Monostable,Astable, and Bistable. Each mode represents a different type of circuit that has a particular output. Astable mode, Bistable Mode (or Schmitt Trigger), Monostable mode.   Question No. 5: Define signal sampling Answer: In signal processing, sampling is the reduction of a continuous signal to a discrete signal. A common example is the conversion of a sound wave (a continuous signal) to a sequence of samples (a discrete-time signal).       Network Analysis Lab Viva Questions and Answers Question No. 6: What is Q factor? Answer: The Q factor is ratio of inductive reactance to resistance of a coil.   Question No. 7: List examples of current sources? Answer: Semiconductor devices like transistor and diode are treated as current sources.   Question No. 8: State Norton’s theorem? Answer: This theorem states that any linear bilateral network with active network with output terminals AB can be replaced by a single current source in parallel with a single impedance Z.   Question No. 9: What is the efficiency during maximum power transfer? Answer: Efficiency during maximum power transfer 50%.   Question No. 10: Define filter? Answer: A filter is an electrical network that can transmit signals within a specified frequency range.    

  Question No. 1: What are the different types of Hydro Schemes? Answer: Different types of Hydro Schemes are: 1.     Purely Run-of-River Power Station. 2.     Storage type Power Station. 3.     Run-of-River Stations withPondage.   Question No. 2: What is a hydro energy? Answer: Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water.   Question No.3 : Why Hydropower stations are preferred solution for meeting peak loads in grids? Answer: Due to its unique capabilities of quick starting and stopping of hydro machines, hydropower stations are found to be economical choice to meet peak load in the grid.   Question No. 4: What is the classification of Hydro Projects based on Installed Capacity & Applicability? Answer: The Hydro Projects Capacity & Applicability are as the following: Large: > 100 MW = Large urban population centres Medium: 10 – 100 MW = Medium urban population centres Small: 1 – 10MW = Small communities with possibility to supply electricity to regional grid. Mini: 100 kW – 1MW = Small factory or isolated communities. Micro: 5 – 100kW = Small isolated communities. Pico: <5kW = 1-2 houses.   Question No. 5: Why Generation Voltage in Thermal Power Plant is between 11 kV to 33 kV? Answer: The current carrying conductor cross section depends upon the magnitude of the current it is carrying and insulation strength of the conductor depends on the maximum voltage it can withstand. Therefore while designing the generator an optimum value is chosen between the amount of the current and voltage conductor can withstand.   Question No. 6: What are the advantages of Hydropower? Answer: The advantages of Hydropower are: 1.     A renewable source of energy – saves scarce fuel reserves. 2.     Nonpolluting and hence environment friendly. 3.     Long life – The first hydro project of India completed in 1897 is still in operation at Darjeeling. 4.     Cost of generation, operation and maintenance is lower than the other sources of energy. 5.     Ability to start and stop quickly and instantaneous load acceptance/rejection makes it suitable to meet peak demand and for enhancing system reliability and stability. 6.     Has higher efficiency (over 90%) compared to thermal (35%) and gas (around 50%). 7.     Cost of generation is free from inflationary effects after the initial installation. 8.     Storage based hydro schemes often provide benefits of irrigation, flood control, drinking water supply, navigation, recreation, tourism etc. 9.     Being located in remote regions leads to development of interior backward areas (education, medical, road communication, telecommunication etc.)   Question No. 7: How efficiency of Thermal Plant can be improved? Answer: Some of the methods by which the efficiency of the thermal plant can be improved are: 1.     By increasing the temperature and pressure of the steam entering the turbine 2.     By reducing the pressure in the condenser 3.     By reheating the steam between different stages between the turbine   Question No. 8: What is the estimated total Hydropower potential of India? Answer: The hydro power potential of India is around 1,48,701 MW and at 60% load factor, it can meet the demand of around 84,000 MW.   Question No. 9: What are approaches to tackle sedimentation problem of reservoir? Answer: The following are some approaches to tackle sedimentation problem of reservoir: 1.     Catchment Area Treatment (CAT) for reduction of silt load includes Afforestation of the catchment area and Environmental works such as construction of check dams. 2.     Effective de-silting arrangements for prevention of silt. 3.     Silt resistant equipment for withstanding the silt.   Question No. 10: What are the different types of dams? Answer: Different types of dams are conventional concrete dam, Roller compacted concrete dam, rock fill dam, Concrete Faced Rock fill Dam (CFRD), Earth fill dam, arch dam, barrages etc.  

Electric field : Force per unit charge.

Electric Power : Electric work done per unit time. P=W/t SI unit is Watt.

TYPES OF SOLAR ELECTRIC SYSTEMS: A solar electric systems generally consists of components such as inverters, charge controllers and batteries. The components required are dependent on the system type designed. System types include: PV-DIRECT SYSTEMS: These are the simplest of solar-electric systems, with the fewest components (basically the PV array and the load). Because they don’t have batteries and are not hooked up to the utility, they only power the loads when the sun is shining. This means that they are only appropriate for a few select applications, notably water pumping and ventilation—when the sun shines, the fan or pump runs. OFF-GRID SYSTEMS: Although they are most common in remote locations without utility service, off-grid solar-electric systems can work anywhere. These systems operate independently from the grid to provide all of a household’s electricity. These systems require a battery bank to store the solar electricity for use during nighttime or cloudy weather, a charge controller to protect the battery bank from overcharge, an inverter to convert the DC PV array power to AC for use with AC household appliances, and all the required disconnects, monitoring, and associated electrical safety gear. GRID-TIED SYSTEMS WITH BATTERY BACKUP: This type is very similar to an off-grid system in design and components, but adds the utility grid, which reduces the need for the system to provide all the energy all the time. BATTERYLESS GRID-TIED SYSTEMS: These most common PV systems are also known as on-grid, grid-tied, utility-interactive, grid-intertied, or grid-direct. They generate solar electricity and route it to the loads and to the electric utility grid, offsetting a home’s or business’s electricity usage. System components are simply comprised of the PV array, inverter(s), and required electrical safety gear (i.e., fuses/breakers/disconnects/monitoring). Living with a grid-connected solar-electric system is no different than living with utility electricity, except that some or all of the electricity you use comes from the sun. (The drawback of these batteryless systems is that they provide no outage protection—when the utility grid fails, these systems cannot operate.)

Ferranti Effect in Power System In general practice we know, that for all electrical systems current flows from the region of higher potential to the region of lower potential, to compensate for the electrical potential difference that exists in the system. In all practical cases the sending end voltage is higher than the receiving end due to line losses, so current flows from the source or the supply end to the load. But Sir S.Z. Ferranti, in the year 1890, came up with an astonishing theory about medium distance transmission line or long distance transmission lines suggesting that in case of light loading or no load operation of transmission system, the receiving end voltage often increases beyond the sending end voltage, leading to a phenomena known as Ferranti effect in power system. Why Ferranti Effect occurs in a Transmission Line? A long transmission line can be considered to compose a considerably high amount of capacitance and inductance distributed across the entire length of the line. Ferranti Effect occurs when current drawn by the distributed capacitance of the line itself is greater than the current associated with the load at the receiving end of the line(during light or no load). This capacitor charging current leads to voltage drop across the line inductor of the transmission system which is in phase with the sending end voltages. This voltage drop keeps on increasing additively as we move towards the load end of the line and subsequently the receiving end voltage tends to get larger than applied voltage leading to the phenomena called Ferranti effect in power system.

Instrumental Transformers - Instrument Transformers are used in AC system for measurement of electrical quantities i.e. voltage, current, power, energy, power factor, frequency. Instrument transformers are also used with protective relays for protection of power system. Basic function of Instrument transformers is to step down the AC System voltage and current. The voltage and current level of power system is very high. It is very difficult and costly to design the measuring instruments for measurement of such high level voltage and current. Generally measuring instruments are designed for 5 A and 110 V. Types of Instrument Transformers Instrument transformers are of two types – 1. Current Transformer (C.T.) 2. Potential Transformer (P.T.) 1. Current Transformer (C.T.) Current transformer is used to step down the current of power system to a lower level to make it feasible to be measured by small rating Ammeter (i.e. 5A ammeter). 2. Potential Transformer (P.T.) Potential transformer is used to step down the voltage of power system to a lower level to make is feasible to be measured by small rating voltmeter i.e. 110 – 120 V voltmeter.

Types of Electrical Insulator | Overhead Insulator There are mainly three types of insulator used as overhead insulator likewise ▶️Pin Insulator ▶️Suspension Insulator ▶️Strain Insulator In addition to that there are other two types of electrical insulator available mainly for low voltage application, i.e. Stay Insulator and Shackle Insulator.

six reasons for motor overheating: 1. MOTOR IS TOO SMALL FOR THE APPLICATION It is important to make sure the motor you are using has been properly sized for the application, environment and duty cycle it will be performing in. A motor that is too small will not be able to dissipate heat quickly enough, and the motor will overheat. 2. HIGH AMBIENT TEMPERATURES If a motor is running in a much warmer environment than it was designed for, it can overheat because the ambient temperatures will make it more difficult for the motor to cool down properly. Check the insulation class of your motor (found on the motor’s nameplate). 3. RUNNING AN INTERMITTENT DUTY MOTOR CONTINUOUSLY It is important to run motors that are rated for intermittent duty applications at or below their duty cycle. In order for the motor to run at its rated performance specs, it needs to have time to cool-down completely between cycles. If the motor is run more frequently than it is supposed to, the motor will still be warm and will become increasingly hotter with each cycle, eventually overheating the motor. 4. HIGH OR LOW VOLTAGE SUPPLY Power supply may be insufficient due to amp draw. In order to overcome load or inertia at a stand-still, the motor’s running current will be much too high under load. Incorrect voltage supply will make the motor work harder and could cause it to overheat. 5. HIGH ALTITUDE Motors cool less efficiently at higher elevations due to the thinner air. If you are at a higher elevation—1000 meters (3300 ft.) above sea level, talk to the manufacturer and make sure your motor is rated accordingly. 6. BLOCKED VENTILATION HOLES This may seem obvious, but the ventilation holes on your motor must be open to allow heat to escape. Check and make sure nothing is blocking them.

EngrX: 🔵Vacuum Circuit Breaker or VCB and Vacuum Interrupter A vacuum circuit breaker is such kind of circuit breaker where the arc quenching takes place in vacuum. The technology is suitable for mainly medium voltage application. For higher voltage vacuum technology has been developed but not commercially viable. The operation of opening and closing of current carrying contacts and associated arc interruption take place in a vacuum chamber in the breaker which is called vacuum interrupter. The vacuum interrupter consists of a steel arc chamber in the centre symmetrically arranged ceramic insulators. The vacuum pressure inside a vacuum interrupter is normally maintained at 10 - 6 bar. The material used for current carrying contacts plays an important role in the performance of the vacuum circuit breaker. CuCr is the most ideal material to make VCB contacts. Vacuum interrupter technology was first introduced in the year of 1960. But still it is a developing technology. As time goes on, the size of the vacuum interrupter is being reducing from its early 1960’s size due to different technical developments in this field of engineering. The contact geometry is also improving with time, from butt contact of early days it gradually changes to spiral shape, cup shape and axial magnetic field contact. The vacuum circuit breaker is today recognized as most reliable current interruption technology for medium voltage switchgear. It requires minimum maintenance compared to other circuit breaker technologies. 🔆Advantages of Vacuum Circuit Breaker or VCB Service life of vacuum circuit breaker is much longer than other types of circuit breakers. There is no chance of fire hazard as oil circuit breaker. It is much environment friendly than SF6 Circuit breaker. Beside of that contraction of VCB is much user friendly. Replacement of vacuum interrupter (VI) is much convenient.