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Concept:

The RMS value is given by:

\(RMS =\sqrt{Mean \space square \space value}\)

After the 10^th entry, the values are repeated.

Hence, n = 10

The mean square value of V is given by:

 \(={0^2+5^2+10^2+20^2+50^2+60^2+50^2+20^2+10^2+5^2\over 10}\)

= 965 V

\(RMS =\sqrt{965}\)

RMS = 31 V

While selecting the wiring system for the home, the number of residents is not considered.

Choice Of Wiring Systems:

While making choice for a wiring system for a home, the following factors should be considered:

1.) Cost of wiring

The initial cost of the wiring system to be chosen or selected is one of the paramount factors to be considered. It should be economical and safe.

2.) Durability

 When making choices for a wiring system, the wiring type should be durable (long-lasting) and should also be of proper specifications and in accordance with the assessed life and type of building to be wired.

3.) Mechanical Protection

The wiring should be protected from mechanical damage during its use.

4.) Appearance

The wiring should provide a good look after its installation. If cleat or casing–capping wiring is used in a modern building, it will spoil the outlook of that building. Conduit wiring is preferred mostly for modern buildings except that it’s expensive.

5.) Safety

When it comes to wiring, safety is one of the most paramount factors to be considered because electrocution is one thing you won’t have the time to give a second thought to. Where there is the possibility of a fire hazard, conduit wiring should be used.

6.) Permanency

The wiring should not deteriorate by the action of weather, fumes, dampness, etc. the cables should be resistant to harsh weather and chemical attacks.

Concept:

Average Value:

The average value can be calculated by dividing the area by time period for one cycle

\({V_{avg}} = \frac{{\frac{1}{2}{V_m}T}}{T} = \frac{{{V_M}}}{2} = 0.5;{V_m}\)

Rms value:

\({V_{rms}} = \sqrt {\frac{1}{T}\mathop \smallint \limits_0^T {{\left( {\frac{{{V_m}}}{T}t} \right)}^2}dt;} ;\)

Vrms = Vm / √3 = 0.577 Vm

Note: The result of RMS value for standard triangular waveform and sawtooth waveform should be remembered as Vm/√3

Application:

Given, 

Peak voltage Vm = 200 V

Time period T = 2 sec

\({V_{avg}} = \frac{{\frac{1}{2} \times 2 \times 200}}{2} = 100V\)

Separately excited DC generator:

• A separately excited DC generator is one whose field winding is supplied by an independent external DC source (like a battery).
• The armature is connected to the prime mover that provides mechanical input to the generator.
• The magnitude of the generated voltage depends upon the speed of armature rotation and the field current, i.e., the greater the speed and field current, the higher the induced voltage.
• The separately excited type DC generators are used for power and lighting purposes. The series DC generator is used in arc lamps for lighting, as a stable current generator, and as a booster.

Improper verification is not a cause of failure in an OH line insulator.

Causes of failure in an overhead insulator:

1.) Porosity

• For overhead transmission lines, Porcelain and stearate insulating material is porous and likely to absorb moisture, if their surfaces are not properly glazed and smoothened.
• The resistance of insulating material will be decreased if it absorbs moisture. And it will increase leakage current. The leakage current may damage the insulator and punch the material permanently.

2.) Poor Mechanical Strength

• The Insulators losses their desired mechanical strength due to certain design defects. Therefore, due to the weight of the conductor and wind loading, Insulator gets broken.

3.) Surface Flash Overdue to Dust and Dirt

• As the line Insulator is directly in contact with an atmospheric condition, dust, and dirt deposit on its surface. This may cause a flashover between the conducting ends of the Insulator.

4.) Internal Impurities Cavities

• While manufacturing the Insulators they may consist of certain impurities, cavities, and/or voids. The breakdown strength of Insulators decreases due to such impurities.

Types of semiconductors

1.) P-Type semiconductor

• When trivalent impurity atoms such as indium, and gallium are added to an intrinsic semiconductor, it is known as a p-type semiconductor.
• These semiconductors have 3 valence electrons, therefore accepting one electron to complete its outermost shell. Hence, it is also known as the acceptor atom impurities.
• The majority of charge carriers are holes & minority of charge carriers are electrons.

2.) N-Type semiconductor

• When pentavalent impurity atoms such as antimony and arsenic are added to an intrinsic semiconductor, it is known as an n-type semiconductor.
• These semiconductors have 5 valence electrons, therefore donating one electron to complete its outermost shell. Hence, it is also known as the donor atom impurities.
• The majority of charge carriers are electrons & minority of charge carriers are holes.

Universal motor

• The universal motor is a type of electric motor that can operate on either AC or DC power and uses an electromagnet as its stator to create its magnetic field.
• It is a commutated series-wound motor where the stator's field coils are connected in series with the rotor windings through a commutator. It is often referred to as an AC series motor.
• The universal motor is very similar to a DC series motor in construction but is modified slightly to allow the motor to operate properly on AC power.
• This type of electric motor can operate well on AC because the current in both the field coils and the armature (and the resultant magnetic fields) will alternate (reverse polarity) synchronously with the supply.
• Hence the resulting mechanical force will occur in a consistent direction of rotation, independent of the direction of applied voltage, but determined by the commutator and polarity of the field coils.

The maximum Power Transfer Method is not used in the load flow analysis of the electric power system.

Method of load flow analysis in power system

1. Gauss-Seidel method
2. Newton Raphson method
3. Fast decoupled load flow method

​A comparison between load flow methods is given below:

Operation of diode:

A diode operates when it is forward biased i.e. anode is connected to a positive terminal and the cathode is connected to the negative terminal of the battery.

The speed of operation of a diode is decided by reverse recovery time (t_rr).

Reverse recovery time is the amount of time the current flows in the reverse direction when the forward current instantaneously switches directions due to residual stored charge.

The greater the reverse recovery time; the slower will be the diode and vice-versa. Thus the diodes with lesser reverse recovery time are preferred.

The reverse recovery of a diode is shown below:

The waveform of induced EMF in a DC motor is:

When one conductor sweeps through under one pole, it is expected to see a uniform flux, thus inducing a constant emf in it. When it sweeps through under the next pole, induced emf is still constant but the polarity is now reversed.

This gives rise to the flat-topped rectangular waveform.

Hence, in a DC motor, if Faraday- Lenz relationship is applied to the triangular-shaped flux wave, it will result in a rectangular-shaped voltage wave.