Question { 2798 }

What is a pulse transformer?? Can it be called as a dc transformer??

Answer

A pulse transformer is a transformer that is optimised for transmitting rectangular electrical pulses (that is, pulses with fast rise and fall times and a relatively constant amplitude). Small versions called signal types are used in digital logic and telecommunications circuits, often for matching logic drivers to transmission lines. Medium-sized power versions are used in power-control circuits such as camera flash controllers. Larger power versions are used in the electrical power distribution industry to interface low-voltage control circuitry to the high-voltage gates of power semiconductors. Special high voltage pulse transformers are also used to generate high power pulses for radar, particle accelerators, or other high energy pulsed power applications.

To minimize distortion of the pulse shape, a pulse transformer needs to have low values of leakage inductance and distributed capacitance, and a high open-circuit inductance. In power-type pulse transformers, a low coupling capacitance (between the primary and secondary) is important to protect the circuitry on the primary side from high-powered transients created by the load. For the same reason, high insulation resistance and high breakdown voltage are required. A good transient response is necessary to maintain the rectangular pulse shape at the secondary, because a pulse with slow edges would create switching losses in the power semiconductors.

The product of the peak pulse voltage and the duration of the pulse (or more accurately, the voltage-time integral) is often used to characterise pulse transformers. Generally speaking, the larger this product, the larger and more expensive the transformer.

Pulse transformers by definition have a duty cycle of less than 0.5; whatever energy stored in the coil during the pulse must be "dumped" out before the pulse is fired again.

Question { 3241 }

What is the role of a Production Engg in a Industry?????

Answer

Roles and Responsibilities of Production Engineers

The manufacturing industry is depends on production engineers to improve efficiency.

Demand for industrial workers will grow by 6 percent between the years 2010 to 2020, according to the Bureau of Labor Statistics. But whether the sector is growing fast or slow, production engineers’ skills are vital to the very competitive manufacturing sector. A bachelor's degree in the industrial engineering disciplines is a basic requirement, but a chemical or civil engineering background may get you hired, too. Production engineers have various roles and responsibilities, including design, devising efficient means to produce parts or products, supporting quality control and confering with management to stay on budget and meet production deadlines.

Design:

A production engineer designs processes, material and workspace layouts to ensure fast and efficient production. He can do this using drafting tools and design software such as computer aided design. It is also his responsibility to make appropriate adjustments on the design based on feedback from colleagues or clients. The engineer also keeps company management informed and up-to-date on the status of the design process.
Cost Estimation

It is the production engineer’s responsibility to estimate the cost of production and come up with cost-saving methods. If there are any changes in the design of the product, he determines the effect of this on production cost and presents it to management for review and implementation. He develops efficient manufacturing methods based on the firm’s budget allocation, always trying to strike the right balance between quality and cost.
Production Scheduling

A manufacturing facility must be able to meet targets and deadlines. Timely delivery -- from the raw materials to the finished products -- is only possible if the production schedule is within realistic forecasts. A production engineer is indispensable for meeting these objectives. It is also his responsibility to make sure that a product conforms to specifications and standards. Therefore, he directs product measurement, inspection, and tests for quality and reliability.
Administration and Other Duties

A production engineer’s duties can involve administrative roles such as assigning junior staff duties and shifts. He appraises employees in the production docket and recommends promotions and demotions. He also serves as an adviser to management regarding production-related purchases, quality control and other pillars of production.

Question { Power Grid, 13783 }

What is GIS (Gas Insulated Switchgear)

Answer

It is very much required to establish an electrical substation at load center. Since, establishing a substation at load center is quite economical and profitable in many aspects. As it reduces length of feeders and due to short length feeders, the quality of voltage regulation improves. But the main obstruction of establishing a substation at load center is space. Generally main load center of any place is situated at very congested place where, sufficient land for establishing conventional electrical substation is very hardly available.

his problem can be solved by using gas insulated switchgear technology. In this type of switchgear, all the necessary components of switchgear can be assembled in very limited space. GIS is a kind of metal enclosed switchgear. That means, all the equipments of the electrical switchgear are enclosed by gas tight metal enclosure and SF6 gas is used as insulation between live parts of the equipments and earthed metal enclosure. This type of switchgear, means, gas insulated switchgear is available from 12 KV system to 800 KV system. For establishing electrical substation in very limited place this type of SF6 insulated electrical switchgear plays the major role.

Gas insulated components of substation are generally,

Electrical bus bars.

Electrical isolators or disconnectors.

Circuit breakers.

Current transformers.

Voltage transformers.

Earth switches.

Surge arrestors or lightning arresters.

The substation, assembled by gas insulated switchgear, is popularly known as gas insulated metal enclosed substation (GIMES). GIMES technology is not very recent invention, it is successfully running for over thirty years. In gas insulated medium voltage switchgear, vacuum technology is used as interrupting purpose and SF6 gas is used as insulation material. Although for both interruption and insulation, SF6 gas is used in many medium voltage GIS system. But for such equipments rated SF6 gas pressures are different for interruption and insulation. SF6 gas pressure for insulating purpose is generally kept below 2.5 bar whereas SF6 gas pressure for interrupting purpose is ranged from 5 bar to 7 bar. As vacuum technology is not available for high voltage, so for GIS or gas insulated switchgear system above 72.5 KV, only SF6 is used both for interruption medium and insulation. There are different types of gas insulated metal enclosed switchgears available depending upon their constructional feature.

Question { PKR, 9942 }

1.What is wind span ,wight span and normal span, and what is the difference for 132kv transmission .

Answer

*The wind span is that on which the wind is assumed to act transversely on the conductors and is taken as half the sum of the two spans, adjacent to the support.In order to take full advantage of towers located on elevated ground, it is usual to allow a wind span of 10 to 15 percent in excess of
the normal span. This additional strength can be used in taking a samll angle of deviation on an intermediate tower, where the actual wind span is less than the design wind span. The angle of deviation to be taken in such cases is approximately given by:

θ =( wl /π T )x x180

Where w = total ind load per unit run of span length of all conductor
carried by the tower,
l = difference between the wind span used for design and the actual
wind span, and
T = the total maximum working tension of all conductors carried by the
tower.


*The weight span is the horizontal distance between the lowest point of the conductors, on the two spans adjacent to the tower . The lowest point is defined as the point at which the tangent to the sag curve, or to the sag curve produced, is horizontal. The weight span is used in the design of cross-arms.

Question { Tata Power, 3546 }

Tell me about Tesla.

Answer

Nikola Tesla (10 July 1856 – 7 January 1943) was a Serbian-American inventor, electrical engineer, mechanical engineer, physicist, and futurist who is best known for his contributions to the design of the modern alternating current (AC) electricity supply system.

Question { Power Grid, 2696 }

What is Tan Delta Test

Answer

TAN DELTA TEST:

A pure insulator when is connected across line and earth, it behaves as a capacitor. In an ideal insulator, as the insulating material which acts as dielectric too, is 100 % pure, the electric current passing through the insulator, only have capacitive component. There is no resistive component of the current, flowing from line to earth through insulator as in ideal insulating material, there is zero percent impurity. In pure capacitor, the capacitive electric current leads the applied voltage by 90°. In practice, the insulator cannot be made 100% pure. Also due to the ageing of insulator the impurities like dirt and moisture enter into it. These impurities provide the conductive path to the current. Consequently, leakage electric current flowing from line earth through insulator has also resistive component.

Hence, it is needless to say that, for good insulator, this resistive component of leakage electric current is quite low. In other way the healthiness of an electrical insulator can be determined by ratio of resistive component to capacitive component. For good insulator this ratio would be quite low. This ratio is commonly known as tanδ or tan delta. Sometimes it is also referred as dissipation factor.

Question { Al-Othman, 3244 }

what is the impedence

Answer

Impedance, denoted Z, is an expression of the opposition that an electronic component, circuit, or system offers to alternating and/or direct electric current.Impedance is a vector (two-dimensional)quantity consisting of two independent scalar (one-dimensional) phenomena: resistance and reactance.

Question { 3705 }

how to check the LRS resistance .......................

Answer

Liquid resitance starter (LRS) ,IN which external
resistance is liquied media which is use for the starting
method of slip ring motor.

for starting of slip ring motor external resistance are
required so that we use liquid (addition of some caustic
soda)as resistance so that it is called as LRS.

Question { 2380 }

What is the main purpose of relay?

Answer

The control circuit functions as the coupling between the input and output circuits. In electromechanical relays, the coil accomplishes this function. A relays Output Circuit is the portion of the relay that switches on the load and performs the same function as the mechanical contacts of electromechanical relays.

Question { 2523 }

Which capacitor is used in ceiling fans ?

Answer

Fans use capacitor-run induction motors. Since a fan is expected to be operated just by the flick of a switch, it has to employ a continuous-rating capacitor in series with its auxiliary winding, which stays energizerd as long as the fan runs. The capacitor used is paper type or oil type.

Question { Power Grid, 2155 }

What are the eligibility criteria for Grant of Maharatna status for PSU???

Answer

Eligibility criteria for Grant of Maharatna status for PSU
1. It should be A Navratna Company
2. Listed on Stock exchange
3. It should have an average annual turnover of 25000 crores for last 3 years.
4. It should have an average annual net worth of 15000 crores for last 3 years.
5. It should have an average annual net profit after tax of more than 5000 crores for last 3 years.
6. It should have the significant Global presence.