TSGENCO AE flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Per-unit impedance base

Z_base equals V_base squared divided by S_base for single-phase values; for three-phase use line-to-line voltage and three-phase VA. Per-unit values are identical on either side of an ideal transformer.

Symmetrical component operator a

The operator a equals one at angle 120 degrees; a squared equals one at angle 240 degrees, and 1 + a + a squared equals zero. It decomposes unbalanced phasors into positive, negative and zero sequences.

Surge impedance loading

SIL equals line-to-line voltage squared divided by surge impedance, where surge impedance is the square root of inductance over capacitance. It indicates the natural power a lossless line carries with flat voltage profile.

Equal-area criterion

A synchronous machine remains transiently stable if the accelerating area between mechanical and electrical power curves equals the available decelerating area before the rotor angle exceeds its limit.

Transformer EMF equation

Root-mean-square induced EMF equals 4.44 times frequency times peak mutual flux times turns. The 4.44 constant arises from 2π divided by root two for sinusoidal flux.

Slip of induction motor

Slip equals synchronous speed minus rotor speed, divided by synchronous speed. Rotor frequency equals slip times supply frequency, and standstill corresponds to slip of one.

Maximum torque slip

Slip at maximum torque equals rotor resistance divided by rotor standstill reactance. Maximum torque itself is independent of rotor resistance, so adding resistance shifts the torque peak to higher slip.

DC machine EMF equation

Generated EMF equals flux per pole times speed in rpm times total armature conductors times number of poles, divided by 60 times number of parallel paths.

Three-phase converter average voltage

A fully controlled three-phase bridge gives average DC voltage of 1.35 times line-to-line voltage times cosine of firing angle. It inverts when the firing angle exceeds ninety degrees.

Buck converter voltage ratio

Output voltage equals duty cycle times source voltage in continuous conduction. The switch conducts for the fraction D of each switching period and the diode carries current otherwise.

Latching versus holding current

Latching current is the anode current needed just after gate pulse removal to keep the thyristor on. Holding current is the lower level below which it turns off.

PWM harmonic benefit

Pulse-width modulation chops the DC bus at high frequency, pushing dominant voltage harmonics to high orders that filters remove easily. Fundamental amplitude is controlled by the modulation index.

Wheatstone bridge balance

The bridge is balanced when the ratio of the two adjacent arms on one side equals the ratio on the other side, giving zero detector current and allowing unknown resistance calculation.

Second-order peak overshoot

Percent overshoot equals one hundred times exponential of minus zeta pi divided by square root of one minus zeta squared. It depends only on damping ratio, not natural frequency.

Routh-Hurwitz criterion

The number of sign changes in the first column of the Routh array equals the number of closed-loop poles in the right half plane. A complete zero row indicates marginal stability.

Gain and phase margin

Gain margin is the negative of the gain in decibels at phase crossover. Phase margin is 180 degrees plus phase angle at gain crossover. Positive values indicate a stable closed-loop system.

Rankine cycle efficiency

Efficiency equals turbine work minus pump work, divided by heat added in the boiler. Superheating, reheat and regeneration raise efficiency by improving the mean temperature of heat addition.

Nozzle choking pressure ratio

For a converging nozzle with specific heat ratio 1.4, mass flow chokes when the exit-to-inlet pressure ratio reaches about 0.528. Below this ratio flow remains constant.

Degree of reaction

Degree of reaction is the enthalpy drop in the moving blades divided by the total stage enthalpy drop. It is zero for a pure impulse stage and about one-half for a fifty-percent reaction stage.

Boiler indirect efficiency

Indirect efficiency equals one hundred minus the sum of percentage losses: dry flue gas, moisture in fuel and air, hydrogen combustion, unburnt carbon, radiation and convection.

Darcy-Weisbach head loss

Friction head loss equals friction factor times length over diameter times velocity squared over twice gravitational acceleration. Laminar friction factor equals 64 divided by Reynolds number.

Pump affinity laws

For geometrically similar pumps, flow varies with speed, head with speed squared, and power with speed cubed. Diameter changes follow the same exponents for impeller trimming estimates.

Net positive suction head

Available NPSH equals atmospheric minus vapour pressure head, plus static suction head, minus suction line losses. It must exceed the pump's required NPSH to avoid cavitation.

Equivalent torque for shaft

Under combined bending moment M and torque T, equivalent torque equals square root of M squared plus T squared. Shaft diameter follows from allowable shear stress using sixteen times equivalent torque over pi.

Terzaghi bearing capacity

Ultimate bearing capacity equals cohesion times Nc plus surcharge times Nq plus half gamma times width times N-gamma, with factors depending on friction angle and footing shape.

Effective stress principle

Effective stress equals total stress minus pore water pressure. Strength, compressibility and settlement of soil depend on effective stress, not total stress.

Manning open channel equation

Velocity equals one over Manning roughness, times hydraulic radius to the two-thirds power, times bed slope to the one-half power. Hydraulic radius is area divided by wetted perimeter.

Dam sliding factor of safety

The sliding factor equals the coefficient of friction times the sum of vertical forces, divided by the sum of horizontal forces. A value of at least one is required; practice demands more.

Average speed equal distances

When equal distances are covered at speeds x and y, average speed is twice the product divided by the sum. This harmonic mean is always below the arithmetic mean.

Compound interest difference

For two years, compound interest minus simple interest equals principal times the square of the annual rate divided by one hundred, squared appropriately in percentage form.

Telangana state formation

Telangana became the twenty-ninth state of India on 2 June 2014 under the Andhra Pradesh Reorganisation Act, with Hyderabad as joint capital for a period of ten years.

Telangana power utilities

TSGENCO generates power, TS TRANSCO transmits it, and TSSPDCL plus TSNPDCL distribute in southern and northern Telangana respectively. Singareni Collieries supplies coal to state thermal stations.