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SSC JE - 2019 (Timings 5 pm to 6 pm)

1. Power System complete Syllabus batch (30 to 40 days)

2. Mock Tests for SSC JE 2019 with Video solution (30 days to 40 days)

From 8th of June

From 13th of June

SSC JE - 2020 (Timings 7 pm to 8 pm)

1. Electrical Machine complete syllabus batch Now with MCQs also

2. Basic Electronics Complete syllabus batch

Special Free Session – 3 PMSubject – All subject mix MCQs

SSC JE – 5 PM (Under SSC Subscription)Subject – BEE (Basic Electrical Engineering)

UPPSC AE – 7 PM (Under UPPSC subscription)Subject – Control System

SSC JE – 10 PM Crash course of SSC JE with MCQs

@ashishsoniwifistudy

True energy = WT = P×T = V.I Cosφ×t…………kwhr

Mechanisms: -

(1) Driving mechanism – P.C., C.C.

(2) Braking mechanism - Permanent magnet

(3) Rotating mechanism – R.D.

(4) Recording/registering mechanism – RGT

Energy Meter

S.R. = Shading ring

S.L. = Shading loop

R.D. = Rotating Disc

C.C. = Current coil

P.C. = Potential coil

RGT = Reduced gear train

PM = Permanent Magnet

S = Spindle

Driving Mechanism: -

• Energy Meter consisting of p.c. and c.c. . P.C. is connected across the load for measurement of vtg and C.C. is connected in series to the load for measurement of current.

• By using driving Mechanism driving torque is produced on the rotating disc due to interaction, of fluxes produced due to p.c. and c.c. coil, currents.

Note: -

• P.C of the energy meter must be highly inductive is required so that error in the measurement of energy is minimized.

• Driving torque is proportional to the power consumed by the load.

Driving Torque (𝐓𝐝): -

𝐓𝐝 ∝ [𝛟𝟏 𝐢𝟐 𝐜𝐨𝐬∠𝛟𝟏 𝐢𝟐 −𝛟𝟐 𝐢𝟏 𝐜𝐨𝐬∠𝛟𝟐 𝐢𝟏]

𝐓𝐝 ∝ 𝐕𝐈 {[𝐜𝐨𝐬 𝟗𝟎 + α − 𝚫 −𝛟 − 𝐜𝐨𝐬 𝟗𝟎° + α + 𝚫 −𝛟 }

𝐓𝐝 ∝ 𝐕𝐈[𝟐 𝐬𝐢𝐧 𝟗𝟎 + α . 𝐬𝐢𝐧(𝚫 − 𝛟)]

𝐓𝐝 ∝ 𝟐 𝐜𝐨𝐬α. [𝐕𝐈 𝐬𝐢𝐧(𝚫 − 𝛟)]

𝟐 𝐜𝐨𝐬α = 𝐜𝐨𝐧𝐬𝐭𝐚𝐧𝐭

𝐓𝐝 ∝ 𝐕𝐈 𝐬𝐢𝐧(𝚫 − 𝛟)

𝐏𝐓 = 𝐕𝐈 𝐜𝐨𝐬.𝛟

𝐏𝐌 = 𝐕𝐈 𝐬𝐢𝐧(𝚫 − 𝛟)

Error in Power: -

𝐏𝐌 − 𝐏𝐓 = 𝐕𝐈 [𝐬𝐢𝐧 𝚫 − 𝛟 − 𝐜𝐨𝐬𝛟]

If 𝚫 = 𝟗𝟎° ⇒ 𝐏𝐌 − 𝐏𝐓 = 𝟎 ⇒ 𝐏.𝐂. 𝐢𝐬 𝐨𝐟 𝐇𝐢𝐠𝐡𝐥𝐲 𝐢𝐧𝐝𝐮𝐜𝐭𝐢𝐯𝐞

• As the p.f. is reduced then the error is increased if the potential coil is not highly inductive.

Lag/Quadrature/p.f. correction coil/shading ring Compensation: -

• Lag coil or shading ring is kept below the potential coil for improving the p.f. of the potential coil, so that 90° phase displacement can be maintained between potential coil voltage and flux.

• Variable resistor is used in case of lag coil for adjustment of the angle.

• The position of shading ring is used for adjustment of the angle. Shading ring is made of copper.

Rotating Mechanism: -

• A low weight aluminum disc is used as a rotating disc for reducing friction.

Braking Mechanism: -

𝐓𝐁 ∝ 𝐍

𝐍 = speed of disc

• Speed correction

• By adjusting the position of P.M. speed of the disc is adjusted.

𝐍 ∝𝟏

𝐝

Registering or recording mechanism:-

• Reduced gear teeth mechanism is used for registering of energy consumed by the load during certain period of time. This energy is cumulatively add-up and hence energy meter is a integrating instrument.

Errors and compensation in energy meter: -

Friction and light load compensation: -

• For compensation of fiction and light load energy measurements, shading loop is used the position of the shading loop can be adjustable along the spindle.

Creepy: -

• If the friction is overcompensated by placing the shading loop very closer to the potential coil then rotating disc rotates very slowly an record the energy without any load current and with potential coil only excited this is called creepy this produces error in the measurement of energy.

• For reducing creeping two holes or/slots are made on the rotating disc and these experiences opposing torque so that disc rotation stops.

• By placing small iron piece on the rotating disc creeping is minimized because this iron piece is attracted by permanent magnet.

Over voltage & over load compensations: -

• Saturable shunt magnet is placed between center and side limbs of shunt magnet for diverting the access Flux due to over voltage

• The saturable series magnet is placed between the limbs of series magnet for diverting access Flux due to over local current.

Formulae: -

(1) Energy meter constant = K =𝐍𝐨 𝐟𝐨 𝐫𝐞𝐯.𝐨𝐟 𝐝𝐢𝐬𝐜

𝐊𝐰𝐡𝐫

K =𝐍

𝐩.𝐭.

(2) Energy measured = 𝐖𝐦 =𝐓𝐨𝐭𝐚𝐥 𝐧𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐑𝐞𝐯𝐨𝐥𝐮𝐭𝐢𝐨𝐧𝐬 𝐚𝐬 𝐩𝐞𝐫 𝐥𝐨𝐚𝐝

𝐊

(3) True energy = 𝐖𝐓 =𝐕𝐈𝐜𝐨𝐬𝛟

𝟏𝟎𝟎𝟎×

𝐭

𝟑𝟔𝟎𝟎……………..kwhr

Where,

I = current in A

Half load = I/2

Full load =I

V=voltage in Volts

T= time in sec.

% εr = 𝐖𝐦−𝐖𝐓

𝐖𝐓× 𝟏𝟎𝟎

If εr = Positive ⇒ Disc runs fast

If εr = Negative ⇒ Disc Runs slow

Testing of energy meter and wattmeter: -

Normal loading: -

Testing time = t= 5 hours

Energy consumed = 𝟒. 𝟔 × 𝟓 = 𝟐𝟑 kwhr = 23 units

1 unit = 10 /-

Cost of testing = 𝟐𝟑 × 𝟏𝟎 = 𝟐𝟑𝟎 /-

Phantom loading/fictitious loading: -

𝐏 = 𝐕𝐈 = 𝟐𝟎 × 𝟏𝟎 = 𝟐𝟎𝟎𝐰 = 𝟎. 𝟐 kw

𝐭 = 𝟓 hours

• Energy = 𝟎. 𝟐 × 𝟓 = 𝟏 kwhr

Cost of testing = 𝟏 × 𝟏𝟎 = 𝟏𝟎/−

• Phantom or fictitious loading is used for testing of energy meter and wattmeter.

• By using this method the cost of calibration is minimized because the power loss is reduced.

• Normal supply voltage is applied to the p.c. and small voltage source with variable resistor is connected to the c.c.

• By adjusting this variable resistor rated current is passing through the C.C.

• Energy meter works on the principal of electromagnetic induction.

1. Magnitude of flux in an energy meter varies _____.a) due to abnormal currents and voltagesb) due to high resistance and inductance valuesc) due to change in the transformer turnsd) due to the induced e.m.f in the windings

2. Energy meter creeps _____a) due to change in supplyb) due to reversal in polarity of voltagec) due to asymmetry in magnetic circuitd) due to turns ratio of transformer

3. Supply voltage in an energy meter is ____a) constant alwaysb) zero alwaysc) depends on the loadd) can fluctuate

4. How is the flux of shunt coil related to voltage?a) flux is proportional to square of voltageb) directly proportionalc) inversely proportionald) independent of each other

5. Creeping is avoided by____a) reversing the polarity of the voltageb) drilling two diametrically opposite holesc) holding the discd) increasing the friction

6. In some energy meters, creeping can be avoided by _____a) attaching small gold piecesb) attaching small aluminium piecesc) attaching small iron piecesd) attaching small zinc pieces

7. measurement of energy involves_____a) inductance and capacitance measurementb) power consumption and time durationc) resistance measurement and voltage dropd) current consumption and voltage drop

8. An energy meter, having meter constant of 1200 rev/kWh,makes 20 revolutions in 30 seconds for a constant load. Theload, in kW, is ______. [2016: 2 Marks, Set-2]

SSC JE-2019

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Electrical Engineering by ASHISH SIR

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Electrical Engineering by ASHISH SIR

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Electrical Engineering by ASHISH SIR

Electrical Engineering by ASHISH SIR

Electrical Engineering by ASHISH SIR

Electrical Engineering by ASHISH SIR

Electrical Engineering by ASHISH SIR

Electrical Engineering by ASHISH SIR

Electrical Engineering by ASHISH SIR

(28) In a steam power plant…………heats the feed water on its way to the boiler by delivering heat from the flue gases: -

(A) Superheater (B) Economizer

(B) Preheater (D) Turbine

(29) Power generation of thermal power plants is based on: -

(A) Rankine cycle

(B) Otto cycle

(C) Diesel cycle

(D) Carnot cycle