JustAnswer
A) Write a report, with diagrams, on three phase circuits to include:
(1) Characteristics
The power generated in power plants is 3-phase power which is transmitted to consumers through transmission lines. The biggest advantage of 3-phase system is that power generated is uniform and it is not pulsating as in 1-phase systems. A balanced 3-phase system has 3 equal phase voltages differing in phase by 1200. In case of 3-phase balanced systems, neutral is not required as algebraic sum of 3-phase currents is zero. Three –phase circuits require less conductor weight than 1-phase systems of similar capacity. Three-phase systems are more efficient. They permit flexibility in selecting voltage and can feed single-phase loads also.
(2) Variations type
Three-phase systems can either be delta connected or star connected as shown below.
[pic]
In delta system, line current = √3*phase current, line voltage = phase voltage.
In star system, line current = phase current, line voltage = √3*phase voltage.
In both systems, Power = √3VLILcosψ, where cosψ is load power factor, VL is line voltage and IL is line current.
As neutral is not available in delta connected system, it is not possible to feed single-phase loads. On the other hand, single-phase loads can be fed in star connected systems as neutral is available.
(3) Applications in the building services industry
As majority of loads in building service industry are single-phase loads, star connected systems are used for feeding such loads. The loads are more or less uniformly distributed on each phase so that load on 3-phase system remains more or less balanced.
Explain the differences between single and three phase circuits
The following table gives differences between single-phase and three-phase systems
| |1-phase |3-phase |
|1 |Pulsating power is generated. Hence, single-phase induction motors make|Uniform power is generated. Three-phase induction motors |
| |noise while in operations. |don’t make that typical noise of single-phase motors. |
|2 |These require more material for transmitting same power as 3-phase |Less material is required. |
| |system. | |
|3. |These are not suitable for feeding large loads. |These are suitable for feeding large loads. |
|4. |Phase voltage is available to feed the loads. |Line voltage as well as phase is available to feed the |
| | |loads. Line voltage = √3*phase voltage |
|5. |These cannot used to transmit power over long distances. |These are used to transmit power over long distances. |
|6 |These are less efficient. |These are more efficient when compared with 1-phase systems.|
B) Solve the following problems :
(i) At what frequency will resonance be achieved in a circuit with a 300 nF capacitor
and a 15 H inductor ?
Frequency f = [pic]
(ii) Calculate the Q factor for a circuit with a 25nf capacitor in series with a 0.03H
inductor and a resistor of 15 Kohms.
[pic]
Hence, [pic]
(iii) What would be the Q factor for the circuit above if the inductor and capacitor
were in parallel ?
Let the circuit be as given below.
[pic]
Resonance frequency remains same.
Q = [pic] as resistance in parallel with L and C is infinite.
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.