Electrical & Electronics Engineering
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Friday 10 November 2017
2)State the difference between generator and alternator
Tuesday 7 November 2017
electrical enginner interview questions
• Starting current is reduced 3-4 times of the direct current due to which voltage drops and hence it causes less losses.
• Star delta starter circuit comes in circuit first during starting of motor, which reduces voltage 3 times, that is why current also reduces up to 3 times and hence less motor burning is caused.
• In addition, starting torque is increased and it prevents the damage of motor winding.
Sunday 4 December 2016
Transformer
Definition of Transformer
A transformer is a static machine used for transforming power from one circuit to another without changing frequency. This is a very basic definition of transformer. Since there is no rotating or moving part so transformer is a static device. Transformer operates on ac supply. Transformer works on the principle of mutual induction.
History of Transformer
If we want to know the history of transformer we have go back long in the 1880s. Around 50 years before that in 1830 property of induction which is the working principle of transformer was discovered. Later the transformer design was improved resulting in more efficiency and lesser size. Gradually the large capacity of transformers in the range of several KVA, MVA came into existence. In the year 1950, 400KV electrical power transformer was introduced in high voltage electrical power system. In the early 1970s, unit rating as large as 1100 MVA was produced and 800KV and even higher KV class transformers were manufactured in year of 1980.
Use of Power Transformer
Generation of electrical power in low voltage level is very much cost effective. Theoretically, this low voltage level power can be transmitted to the receiving end. This low voltage power if transmitted results in greater line current which indeed causes more line lossesBut if the voltage level of a power is increased, the current of the power is reduced which causes reduction in ohmic or I2R losses in the system, reduction in cross sectional area of the conductor i.e. reduction in capital cost of the system and it also improves the voltage regulation of the system. Because of these, low level power must be stepped up for efficient electrical power transmission. This is done by step up transformer at the sending side of the power system network. As this high voltage power may not be distributed to the consumers directly, this must be stepped down to the desired level at the receiving end with the help of step down transformer. Electrical power transformer thus plays a vital role in power transmission. Two winding transformers are generally used where ratio of high voltage and low voltage is greater than 2. It is cost effective to use auto transformer where the ratio between high voltage and low voltage is less than 2. Again a single unit three phase transformer is more cost effective than a bank of three single phase transformers unit in a three phase system. But a single three phase transformer unit is a bit difficult to transport and have to be removed from service entirely if one of the phase winding breaks down.
Types of Transformer
Transformers can be categorized in different ways, depending upon their purpose, use, construction etc. The types of transformer are as follows,
Step Up Transformer & Step Down Transformer - Generally used for stepping up and down the voltage level of power in transmission and distribution power system network.
Three Phase Transformer & Single Phase Transformer - Former is generally used in three phase power system as it is cost effective than later. But when size matters, it is preferable to use a bank of three single phase transformer as it is easier to transport than one single three phase transformer unit.Electrical Power Transformer, Distribution Transformer & Instrument Transformer - Power transformers are generally used in transmission network for stepping up or down the voltage level. It operates mainly during high or peak loads and has maximum efficiency at or near full load. Distribution transformer steps down the voltage for distribution purpose to domestic or commercial users. It has good voltage regulation and operates 24 hrs a day with maximum efficiency at 50% of full load. Instrument transformers include C.T & P.T which are used to reduce high voltages and current to lesser values which can be measured by conventional instruments. Two Winding Transformer & Auto Transformer - Former is generally used where ratio between high voltage and low voltage is greater than 2. It is cost effective to use later where the ratio between high voltage and low voltage is less than 2. Outdoor Transformer & Indoor Transformer - Transformers that are designed for installing at outdoor are outdoor transformers and transformers designed for installing at indoor are indoor transformers.Oil Cooled & Dry Type Transformer - In oil cooled transformer the cooling medium is transformer oil whereas the dry type transformer is air cooled.Core type, Shell type & Berry type transformer - In core type transformer it has two vertical legs or limbs with two horizontal sections named yoke. Core is rectangular in shape with a common magnetic circuit. Cylindrical coils (HV & LV) are placed on both the limbs. Shell type transformer: It has a central limb and two outer limbs. Both HV, LV coils are placed on the central limb. Double magnetic circuit is present. Berry type transformer: The core looks like spokes of wheels. Tightly fitted metal sheet tanks are used for housing this type of transformer with transformer oil filled inside
Beautiful Message
*Beautiful Message*!!
💬 If You Are Right Then There is No Need to Get Angry ...
💬 And If You Are Wrong Then You Don't Have Any Right to Get Angry.
💬 Patience With Family is Love .....
💬 Patience With Others is Respect.
💬 Patience With Self is Confidence And Patience With GOD is Faith.
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💬 Don't Think More About The FUTURE , It Brings Fear...
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💬 Every Problem Comes To Make Us Or Break Us !
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Do Share It , With All The Good People In Your Life.
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Saturday 3 December 2016
Present engineers job hunting in india and choosing different jobs
An unemployed B.TECH graduate was looking out for a
suitable job in his stream.
He attended several
exams and many personal interviews, only to be
rejected.
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Being fed up after so many months of his
job hunt, he decided to get into any job that can
satisfy his food and daily needs.
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He visited a
circus group and asked for a job.
But the owner
said that there wasn't any job for his education
level. Also he said that there is a vacancy to act
as a monkey and perform funny actions. The
unemployed youth accepted the offer since he can
at least afford his daily food.
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So he dressed up as a monkey and entertained the
audience. One day while he was performing the
monkey skills, he accidentally fell into the lion's
ring.
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Everyone was shocked as the monkey fell into
lion's ring. No one knew that he was a man
dressed up as a monkey.
The man himself was
dreadful and feared for his life.
He felt pity for
himself as he going to be a victim of
unemployment.
.
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The lion came closer to him but didn't attack. He
was surprised. Then the lion spoke, "ghabra mat!! main M.TECH hoon Salle.. "
Friday 2 December 2016
APTRANSCO SUB ENGINEER PREVIOUS QUESTION PAPER
(A) conductively linked.
(C) not linked at all.
Ans : B
(A) at no load, it will rotate at dangerously high speed.
(B) it will fail to start.
(C) it will not develop high starting torque.
(D) all are true.
Ans: A
(A) 50 Hz.
(C) 2 Hz.
Ans: C
(A) low at light load only.
(B) low at heavy load only.
(C) low at light and heavy load both.
(D) low at rated load only.
Ans: A
(A) between 11 KV and 33 KV.
(C) between 400 KV and 700 KV.
Ans: A
produces
(A) damping torque.
(B) eddy current torque.
(C) torque aiding the developed torque.
(D) no torque.
Ans: D
voltage will be
(A) A square wave.
(C) A triangular wave.
Ans: A
(A) Ia
(B) (Ia)2
(A) stationary w.r.t. armature.
Ans: C
(A) applied voltage
(C) circuit configuration
Ans: D
(A) can run at synchronous speed only
(B) can run at sub synchronous speed only
(C) can run at synchronous and super synchronous speed
(D) can run at synchronous and sub synchronous speed
(A) Eddy current loss
(C) copper losses
Ans: A
(A) lags the applied voltage by 90°
(B) lags the applied voltage by somewhat less than 90°
(C) leads the applied voltage by 90°
(D) leads the applied voltage by somewhat less than 90°
Ans: B