Electrical Concepts

1) What is the difference between Cable and wire ?

Answer- Cable is set of conductor and wire is single conductor.

2) We can store power in only DC (Direct Current) and not in AC ( Alternating current)

3) In induction motor 1-Phase motor is not self starting but 3-Phase induction motor is self starting.

4) Load is the anything that consume power that is losses. Example- bulb,fan, motor.

5) 'k' in kW, kVA, kA, kV need to be in smaller case and not as in KW, KVA, KA, KV.

6) Circuit Breaker is the work as a switching device after receiving command from relay it will not sense the abnormality in the system.

7) mili- 10^-3, micro- 10^-6, nano- 10^-9, pico- 10^-12, kilo-10^3, mega-10^6, Gega- 10^9.

Useful mathematics formulas

(α+в+¢)²= α²+в²+¢²+2(αв+в¢+¢α)
1. (α+в)²= α²+2αв+в²
2. (α+в)²= (α-в)²+4αв b
3. (α-в)²= α²-2αв+в²
4. (α-в)²= f(α+в)²-4αв
5. α² + в²= (α+в)² - 2αв.
6. α² + в²= (α-в)² + 2αв.
7. α²-в² =(α + в)(α - в)
8. 2(α² + в²) = (α+ в)² + (α - в)²
9. 4αв = (α + в)² -(α-в)²
10. αв ={(α+в)/2}²-{(α-в)/2}²
11. (α + в + ¢)² = α² + в² + ¢² + 2(αв + в¢ + ¢α)
12. (α + в)³ = α³ + 3α²в + 3αв² + в³
13. (α + в)³ = α³ + в³ + 3αв(α + в)
14. (α-в)³=α³-3α²в+3αв²-в³
15. α³ + в³ = (α + в) (α² -αв + в²)
16. α³ + в³ = (α+ в)³ -3αв(α+ в)
17. α³ -в³ = (α -в) (α² + αв + в²)
18. α³ -в³ = (α-в)³ + 3αв(α-в)
ѕιη0° =0
ѕιη30° = 1/2
ѕιη45° = 1/√2
ѕιη60° = √3/2
ѕιη90° = 1
¢σѕ ιѕ σρρσѕιтє σƒ ѕιη
тαη0° = 0
тαη30° = 1/√3
тαη45° = 1
тαη60° = √3
тαη90° = ∞
¢σт ιѕ σρρσѕιтє σƒ тαη
ѕє¢0° = 1
ѕє¢30° = 2/√3
ѕє¢45° = √2
ѕє¢60° = 2
ѕє¢90° = ∞
¢σѕє¢ ιѕ σρρσѕιтє σƒ ѕє¢
2ѕιηα¢σѕв=ѕιη(α+в)+ѕιη(α-в)
2¢σѕαѕιηв=ѕιη(α+в)-ѕιη(α-в)
2¢σѕα¢σѕв=¢σѕ(α+в)+¢σѕ(α-в)
2ѕιηαѕιηв=¢σѕ(α-в)-¢σѕ(α+в)
ѕιη(α+в)=ѕιηα ¢σѕв+ ¢σѕα ѕιηв.
» ¢σѕ(α+в)=¢σѕα ¢σѕв - ѕιηα ѕιηв.
» ѕιη(α-в)=ѕιηα¢σѕв-¢σѕαѕιηв.
» ¢σѕ(α-в)=¢σѕα¢σѕв+ѕιηαѕιηв.
» тαη(α+в)= (тαηα + тαηв)/ (1−тαηαтαηв)
» тαη(α−в)= (тαηα − тαηв) / (1+ тαηαтαηв)
» ¢σт(α+в)= (¢σтα¢σтв −1) / (¢σтα + ¢σтв)
» ¢σт(α−в)= (¢σтα¢σтв + 1) / (¢σтв− ¢σтα)
» ѕιη(α+в)=ѕιηα ¢σѕв+ ¢σѕα ѕιηв.
» ¢σѕ(α+в)=¢σѕα ¢σѕв +ѕιηα ѕιηв.
» ѕιη(α-в)=ѕιηα¢σѕв-¢σѕαѕιηв.
» ¢σѕ(α-в)=¢σѕα¢σѕв+ѕιηαѕιηв.
» тαη(α+в)= (тαηα + тαηв)/ (1−тαηαтαηв)
» тαη(α−в)= (тαηα − тαηв) / (1+ тαηαтαηв)
» ¢σт(α+в)= (¢σтα¢σтв −1) / (¢σтα + ¢σтв)
» ¢σт(α−в)= (¢σтα¢σтв + 1) / (¢σтв− ¢σтα)
α/ѕιηα = в/ѕιηв = ¢/ѕιη¢ = 2я
» α = в ¢σѕ¢ + ¢ ¢σѕв
» в = α ¢σѕ¢ + ¢ ¢σѕα
» ¢ = α ¢σѕв + в ¢σѕα
» ¢σѕα = (в² + ¢²− α²) / 2в¢
» ¢σѕв = (¢² + α²− в²) / 2¢α
» ¢σѕ¢ = (α² + в²− ¢²) / 2¢α
» Δ = αв¢/4я
» ѕιηΘ = 0 тнєη,Θ = ηΠ
» ѕιηΘ = 1 тнєη,Θ = (4η + 1)Π/2
» ѕιηΘ =−1 тнєη,Θ = (4η− 1)Π/2
» ѕιηΘ = ѕιηα тнєη,Θ = ηΠ (−1)^ηα

1. ѕιη2α = 2ѕιηα¢σѕα
2. ¢σѕ2α = ¢σѕ²α − ѕιη²α
3. ¢σѕ2α = 2¢σѕ²α − 1
4. ¢σѕ2α = 1 − ѕιη²α
5. 2ѕιη²α = 1 − ¢σѕ2α
6. 1 + ѕιη2α = (ѕιηα + ¢σѕα)²
7. 1 − ѕιη2α = (ѕιηα − ¢σѕα)²
8. тαη2α = 2тαηα / (1 − тαη²α)
9. ѕιη2α = 2тαηα / (1 + тαη²α)
10. ¢σѕ2α = (1 − тαη²α) / (1 + тαη²α)
11. 4ѕιη³α = 3ѕιηα − ѕιη3α
12. 4¢σѕ³α = 3¢σѕα + ¢σѕ3α

» ѕιη²Θ+¢σѕ²Θ=1
» ѕє¢²Θ-тαη²Θ=1
» ¢σѕє¢²Θ-¢σт²Θ=1
» ѕιηΘ=1/¢σѕє¢Θ
» ¢σѕє¢Θ=1/ѕιηΘ
» ¢σѕΘ=1/ѕє¢Θ
» ѕє¢Θ=1/¢σѕΘ
» тαηΘ=1/¢σтΘ
» ¢σтΘ=1/тαηΘ
» тαηΘ=ѕιηΘ/¢σѕ

What is the difference between Resistance , reactance and inductance

What is the difference between Resistance , reactance and inductance

Resistance is the term which  oppose the  flow of current.Usually denoted by R.
Resistance is depend on material.

Reluctance is occure in ac power which oppose the flow of current in capacitor and inductor. reactance is not applicable in DC circuit.

There are two types of Reactance these are Inductive Reactance and Capacitive Reactance.

1) Inductive Reactance.
 When AC current flow through an Inductanace a back Emf or voltage is devloped opposing any change in the initial current.this opposition to flow of current is called inductive reactanance.

2) Capacitive reactance
When an Ac current flow through an capacitance a oppsing in intial voltage is occur this oppsing prperty is called Capacitive reactance.

For capacitors X=1/(2ΠfC); where f is the frequency,C is the capacitance.

For inductors X= 2ΠfL; where f is the frequency,:L is the inductance.

Impedance is the sum of the resistance and reactance of a circuit

denoted by Z=R+jX (for primarily inductive cirucits) or Z=R-jX (for primarily capacitive circuits).

Thanks,

Kiran Patil

Why single phase motor is not self starting

Title- why single phase motor is not self starting.

Theory- 

Why Single Phase Induction Motor is not Self Starting?

But what about single phase. It will be having only one phase still it makes the rotor to rotate, so it is quite interesting. Before that we need to know why single phase induction motor is not a self starting motor and how the problem is overcome. We know that the ac supply is a sinusoidal wave and it produces pulsating magnetic field in uniformly distributed stator winding. Since pulsating magnetic field can be assumed as two oppositely rotating magnetic field, there will be no resultant torque produced at the starting and due to this the motor does not run. After giving the supply, if the rotor is made to rotate in either direction by external force, then the motor will start to run. This problem has been solved by making the stator winding into two winding, one is main winding and another is auxiliary winding and a capacitor is fixed in series with the auxiliary winding. This will make a phase difference when Electric current will flow through the both coils. When there will be phase difference, the rotor will generate a starting torque and it will start to rotate. Practically we can see that the fan does not rotate when the capacitor is disconnected from the motor but if we rotate with hand it will start to rotate. So this is the reason of using capacitor in the single phaseinductin motor There are several advantages of  induction motor which makes this motor to have wider application. It is having good efficiency up to 97%. But the speed of the motor varies with the load given to the motor which is an disadvantage of this motor. The direction of rotation of induction motor can easily be changed by changing the sequence of three phase supply, i.e. if RYB is in forward direction, the RBY will make the motor to rotate in reverse direction. This is in the case of three phase motor but in single phase motor, the direction can be reversed by reversing the cpacitor terminals in the winding.
Regards,
Kiran Patil

Electrical engineering facts.

Some basic facts an Electrical Engineer should know..!

1. You need to know Ohm's law V=IR, current is proportional to the voltage applied.

2. Electric shock is caused by current and not voltage. 30mA of current is enough to cause ventricular fibrillation in your heart.

3. Megger  is the name of a company. (Many people term measuring of Insulation resistance as Megger)

4. 'Exd' type equipments (sometimes called explosion proof) do not prevent explosion. They just help to isolate an explosion in the interior of the equipment from spreading outside.

5. Test before Touch. This is a mantra that every electrical engineer should remember. You need to check that there is no voltage before touching any live part. It may have been fed from a different source.

6. Nowadays, domestic fan regulators do not work on potential divider concept and there is no power loss if you operate the fan at lower/higher speeds.

7. System earthing and body earthing are different.

8. All motors are treated in kW/MW, transformers in MVA/kVA and fuses in A.

9. 'k' in kW, kVA, kA, kV need to be in smaller case and not as in KW, KVA, KA, KV.

10. Incidents can happen anytime and one should wear appropriate safety gear before working on an electrical installation.

11. In electrical cables, size of the core determines the amount of current it can carry and the thickness of Insulation determines the voltage level it can work at.

12. Making capacity of a circuit breaker is approximately 2.5 times its breaking capacity.

13. In transformers, Dyn11 vector group will become Yd1 if you change its primary and secondary sides.

14. Neutral is solidly grounded in the 415V system at the user end to protect people from shock.

15. 230V, that we measure is the rms value and the actual peak AC voltage is √2 * 230V.

16. Every electrical engineer should know how to give basic first aid and CPR. CPR can bring a dead person to life.

17. Zero watt bulbs available in the market are not actually rated for zero watt. Their ratings vary from 5W to 20W.

Title : How to calculate resistivity of resister using colour code.

Colour code table

Band Colour	1st Band	2nd Band	Multiplier x	Tolerance
Silver			÷ 100	10%
Gold			÷ 10	5%
Black	0	0	1
Brown	1	1	10	1%
Red	2	2	100	2%
Orange	3	3	1000
Yellow	4	4	10,000
Green	5	5	100,000
Blue	6	6	1,000,000
Violet	7	7
Grey	8	8
White	9	9

Hint for remember colour code - BB ROY Goes to Britten Visky Given by Wife ( you can also make other sentence)

Example: Band 1 = Red, Band 2 = Violet, Band 3 = Orange, Band 4 = Gold			Too many zeros?
The value of this resistor would be:			kilo ohms and mega
2 (Red) 7 (Violet) x1,000 (Orange)	= 27 x 1,000		ohms can be used:
	= 27,000 with a 5% tolerance (gold)		1,000 ohms =1k
	= 27k ohms Note- SILVER and GOLD for tolerance as per shown in chart similararly if 4th band is absent on resistor means its 20% tolerence (for no band)