Indepth Electrical engineering

Circuit Breakers Utilization Categories, Releases, Ratings & Markings Circuit breakers are essential protective devices in electrical systems. They not only interrupt fault currents but also ensure selective coordination with other protective devices. To understand their performance and applications, we need to study their utilization categories, types of releases, rated values, tripping characteristics, and marking requirements. 1. Utilization Categories of Circuit Breakers The utilization category of a circuit breaker specifies whether it is designed for selectivity under short-circuit conditions. There are two main categories: (i) Category A Not designed for selectivity under short-circuit conditions. Do not have intentional short-time delay. No short-time withstand current rating. Commonly used for final distribution protection (e.g., MCCBs in feeders). (ii) Category B Designed for selectivity under short-circuit conditions. Have an intentional s...

Rated short-circuit making capacity (Icm) The rated short-circuit making capacity of a circuit-breaker is the value of short-circuit capacity assigned to that circuit-breaker by the manufacturer for the rated operational making voltage at rated frequency and at a specified power factor for A.C., or time constant for D.C. It is expressed as the maximum prospective peak current. For a c the rated short-circuit making capacity of a circuit-breaker shall be not less than its rated ultimate short-circuit breaking capacity, multiplied by the factor n of table as below  . For d c the rated short-circuit making capacity of a circuit-breaker shall be not less than its rated ultimate short-circuit breaking capacity. A rated short-circuit making capacity implies that the circuit-breaker shall be able to make the current corresponding to that rated capacity at the appropriate applied voltage related to the rated operational voltage. Rated short-circuit breaking capaciti...

Alternator in Cars Alternators are used in cars to generate current for running of cars. We quite often get confused that why alternator is required when there is battery available in cars. Battery in cars is only used for starting the cars, but for lights operation and functioning of other parts current is required now from where that power will come??? For fulfilling the above purpose alternator is required, alternator has following functions in cars:- (i)             Running of lights, heater, Air conditioners and operation of other electrical accessories (ii)           Recharging of battery as it get discharged during starting. Now how this alternator works in cars and who provides mechanical power to alternator so that power output can be generated at alternator output?? When you switched off your car engine than radio of car will work on car battery. For e...

There are following procedure to be adopted for correct dimensioning of a plant (i)             Load Analysis:- First step in dimensioning of a plant is to check for connected load and their location Now check for location of power distribution panels Now we can calculate cable requirement i.e. length of cables and path of cable laying Now we will do calculations of total power consumption while taking account utilization factors and demand factors (ii)           Transformer and generator size calculations:- Transformer and generator size are usually selected 15-30% more in comparison to total connected load considering future prospectus. (iii)          Conductor size selection - Now we calculate cable size according to load requirement of various connected loads. Cable selected may be copper or aluminum. Cables sel...