Selection Criteria of Distribution System - Three Phase or Single Phase

Three phase systems are employed when a large amount of power is to be transferred economically. This note article describes the advantages of three phase system over a single phase system in brief. The criteria for selection of single phase or three phase system is also given.

Summary

Three phase systems are employed when a large amount of power is to be transferred economically. This note article describes the advantages of three phase system over a single phase system in brief. The criteria for selection of single phase or three phase system is also given.

Things to Remember

  1. Three phase systems are more economical if a large amount of power is to be transmitted.
  2. Three phase systems require fewer conductors than an equivalent single-phase system for the transmission of the same amount of power.
  3. Motors, which are the primary equipment in industries aren't available for large ratings in single phase system. So three phase system is required for motors demanding higher power.

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Subjective Questions

Q1:

Write short notes on Penicillin.


Type: Short Difficulty: Easy

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Answer: <h3>Penicillin</h3>
<p>It is an antibiotic or group of antibiotics produced naturally by certain blue moulds, now usually prepared synthetically. They are &beta;-lactam antibiotics and are used in the treatment of bacterial infection caused by staphylococci and streptococci.</p>
<p>&nbsp;</p>
<p>Based on the antimicrobial spectrum it can be classified into following types:</p>
<ol>
<li>
<h4>Natural penicillin</h4>
</li>
</ol>
<p>Natural penicillin, the first agents in the penicillin family, are obtained directly from the Penicillium mold and do not require further modification. They are very active against gram-positive cocci and ineffective against most strains of staphylococcus aureus. These are:</p>
<table>
<tbody>
<tr>
<td width="163">
<p><strong>Drug name</strong></p>
</td>
<td width="178">
<p><strong>Preparation</strong></p>
</td>
<td width="170">
<p><strong>Availability</strong></p>
</td>
</tr>
<tr>
<td width="163">
<p>Benzathine penicillin</p>
</td>
<td width="178">
<p>Injection</p>
</td>
<td width="170">
<p>600000 IU, 1.2 million units and 2.4 mill units per viral</p>
</td>
</tr>
<tr>
<td width="163">
<p>Penicillin G potassium</p>
</td>
<td width="178">
<p>Injection</p>
</td>
<td width="170">
<p>1,2,3,5 million units per viral</p>
</td>
</tr>
<tr>
<td width="163">
<p>Penicillin G procaine</p>
</td>
<td width="178">
<p>Injection</p>
</td>
<td width="170">
<p>6,00,000 units,1.2 million units, 2.4 million units</p>
</td>
</tr>
<tr>
<td width="163">
<p>penicillin V</p>
</td>
<td width="178">
<p>Tablet/Suspension</p>
</td>
<td width="170">
<p>250mg, 500mg/125mg and 250mg per 5 ml</p>
</td>
</tr>
</tbody>
</table>
<p>&nbsp;</p>
<p>&nbsp;</p>
<ol start="2">
<li>
<h4>Penicillinase-resistant penicillin</h4>
</li>
</ol>
<p>The penicillinase-resistant penicillin (also called as antistaphylococcal penicillin) is useful in treating infections caused by Staphylococcus aureus and Staphylococcus epidermis. Antistaphylococcal are the only penicillins that by themselves are resistant to penicillinases. These are:</p>
<p>&nbsp;</p>
<table width="534">
<tbody>
<tr>
<td width="182">
<p><strong>Drug name</strong></p>
</td>
<td width="176">
<p><strong>Preparation</strong></p>
</td>
<td width="176">
<p><strong>Availability</strong></p>
</td>
</tr>
<tr>
<td width="182">
<p>Cloxacillin</p>
</td>
<td width="176">
<p>Capsule</p>
<p>Suspension</p>
</td>
<td width="176">
<p>250 mg, 500 mg</p>
<p>125 mg/5ml</p>
</td>
</tr>
<tr>
<td width="182">
<p>Dicloxacillin</p>
</td>
<td width="176">
<p>Capsule</p>
<p>Suspension</p>
</td>
<td width="176">
<p>250 mg, 500 mg</p>
<p>125 mg/5ml</p>
</td>
</tr>
<tr>
<td width="182">
<p>Flucloxacillin</p>
</td>
<td width="176">
<p>Capsule</p>
</td>
<td width="176">
<p>250 mg, 500 mg</p>
</td>
</tr>
<tr>
<td width="182">
<p>Nafcillin</p>
</td>
<td width="176">
<p>Capsule</p>
<p>injection</p>
</td>
<td width="176">
<p>250 mg</p>
<p>500 mg, 1gm, 2gm</p>
</td>
</tr>
<tr>
<td width="182">
<p>Oxacillin</p>
</td>
<td width="176">
<p>Capsule</p>
<p>Suspension</p>
<p>Injection</p>
</td>
<td width="176">
<p>250 mg, 500 mg</p>
<p>125 mg/5ml</p>
<p>250 mg, 500 mg, 1gm, 2gm</p>
</td>
</tr>
</tbody>
</table>
<p>&nbsp;</p>
<ol start="3">
<li>
<h4>Broad spectrum penicillins</h4>
</li>
</ol>
<p>Broad spectrum penicillins are effective against gram-positive cocci and some gram-negative bacteria (eg. Haemophilus influenza E. coli, Proteus etc.). These are:</p>
<p>&nbsp;</p>
<table width="534">
<tbody>
<tr>
<td width="186">
<p><strong>Drug name</strong></p>
</td>
<td width="170">
<p><strong>Preparation</strong></p>
</td>
<td width="178">
<p><strong>Availability</strong></p>
</td>
</tr>
<tr>
<td width="186">
<p>Amoxicillin</p>
</td>
<td width="170">
<p>Tablet</p>
<p>Capsule</p>
<p>Suspension</p>
</td>
<td width="178">
<p>125 mg, 250 mg, 500 mg</p>
<p>250 mg, 500 mg</p>
<p>100mg/5ml, 125mg/5ml, 250mg/5ml</p>
</td>
</tr>
<tr>
<td width="186">
<p>Amoxicillin and Clavulanate</p>
<p>(Augmentin)</p>
</td>
<td width="170">
<p>Tablet</p>
<p>Suspension</p>
<p>Injection</p>
</td>
<td width="178">
<p>375 mg, 625 mg</p>
<p>156 mg/5ml</p>
<p>150mg, 300mg, 600mg, 1.2gm</p>
</td>
</tr>
<tr>
<td width="186">
<p>Ampicillin</p>
</td>
<td width="170">
<p>Capsule</p>
<p>Suspension</p>
<p>Injection</p>
</td>
<td width="178">
<p>250 mg, 500 mg</p>
<p>125mg/5ml, 250mg/5ml</p>
<p>150mg, 250mg, 500mg, 1gm, 2gm</p>
<p>&nbsp;</p>
</td>
</tr>
<tr>
<td width="186">
<p>Ampicillin and sulbactam</p>
<p>(flucloxacillin and Ampicillin)</p>
</td>
<td width="170">
<p>Tablet</p>
<p>Injection</p>
</td>
<td width="178">
<p>375mg</p>
<p>105gm, 3gm per viral</p>
</td>
</tr>
</tbody>
</table>
<p>&nbsp;</p>
<p>&nbsp;</p>
<ol start="4">
<li>
<h4>Extended spectrum penicillins</h4>
</li>
</ol>
<p>These are effective against Pseudomonas aeruginosin (one of the major pathogens responsible for nosocomial pneumonia) and certain indole-positive Proteus species that are resistant to aminopenicillins. These are:</p>
<p>&nbsp;</p>
<table>
<tbody>
<tr>
<td width="178">
<p><strong>Drug name</strong></p>
</td>
<td width="178">
<p><strong>Preparation</strong></p>
</td>
<td width="178">
<p><strong>Availability</strong></p>
</td>
</tr>
<tr>
<td width="178">
<p>Carbencillin</p>
</td>
<td width="178">
<p>Tablet</p>
</td>
<td width="178">
<p>382 mg</p>
</td>
</tr>
<tr>
<td width="178">
<p>Piperacillin/ Tazobactam</p>
</td>
<td width="178">
<p>Injection</p>
</td>
<td width="178">
<p>2.5gm, 3.375gm, 4.5gm</p>
</td>
</tr>
<tr>
<td width="178">
<p>Ticarcillin/ plus Clavulanate</p>
</td>
<td width="178">
<p>Injection</p>
</td>
<td width="178">
<p>1gm, 3gm, 5gm per viral</p>
</td>
</tr>
</tbody>
</table>
<p>&nbsp;</p>

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Penicillin
Selection Criteria of Distribution System - Three Phase or Single Phase

Selection Criteria of Distribution System - Three Phase or Single Phase

Selection criteria of distribution system - three phase or single phase

Generally, single phase supplies are used for supplying electricity to households and small business ventures. However, a single phase system of distribution is not the best choice for powering up the appliances of industries and large business ventures. The industries of present world are getting more power hungry and require a larger amount of power to run their appliances.

There is a limit to the number of electric appliances a single phase system can power. If a farmer wishes to install powerful motor-driven equipment in his farm, single phase system may not be able to deliver the required amount of power. Similar is the case for business ventures such as rice mills. It should also be noted that the equipment shouldn't cause low voltage problems to other customers.

Three phase systems use lesser number of conductors than an equivalent single-phase system. A single phase system employs two conductors: one acting as the current delivering path and the other acting as the return path. A three phase system employs three or four conductors depending upon the configuration. The fourth wire or the neutral wire enables the system to operate at higher voltage levels while still being able to power lower voltage single phase appliances. The ratio of power transferred to investment is also high which means that for a small increase in the cost of installation, the amount of power transferred is significantly higher than the single phase systems. It is uneconomical to increase the number of phases above three as the conductor and installation cost exceeds the reasonable amount of power transferred.

Therefore, it is absolutely necessary to consider the type of distribution system. Single phase supply may be suitable to power the appliances of households but industries need to consider choosing a three phase system to power their appliances. A distribution system that has been designed properly can ensure a good and reliable supply of electric power to power up multiple appliances without creating an overload on a particular phase.

In general practice, three phase system is used to power the motors requiring a power greater than 5 hp. Single phase systems can be used for motors demanding power less than 5 hp. The usual practice of NEA is to provide single phase supply to households or small business ventures demanding 60 A load (13.2 KVA). If the building is very large and requires more power, a three phase supply is given up to 60 A per phase. The maximum demand in the system, in this case, is approximately 40 KVA.

Lesson

Design of Rural Electrification Network

Subject

Electrical Engineering

Grade

Engineering

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