Indepth Electrical engineering

Three-phase power — single-phase + three-phase loads explained (clean, compact & worked examples) Key rules  Power adds. Whether a load is single-phase or three-phase, its real power (kW) adds algebraically. A statement like “three-phase load = 90 kW” means total three-phase real power = 90 kW (i.e., 30 kW per phase in a balanced system), not 90 kW per phase. For balanced three-phase loads, you can convert total ↔ per-phase by dividing or multiplying by 3: P phase = P total / 3 P_{\text{phase}} = P_{\text{total}}/3 P total = 3 × P phase P_{\text{total}} = 3 \times P_{\text{phase}} Important formulas Total three-phase real power (line-to-line voltage) P 3φ    ( kW ) = 3    V L − L    I    P F 1000 P_{\text{3φ}}\;(\text{kW})=\dfrac{\sqrt{3}\;V_{L-L}\;I\;PF}{1000} where V L − L V_{L-L} is line-to-line RMS voltage, I I is line current (A), and P F PF is power factor. Total three-phase real power (line-to-neutral / per-phase voltage) P 3φ    ( kW...

National Electrical Code (NFPA 70) – Working Spaces for 600 V Electrical Equipment In electrical installations, providing adequate working space around electrical equipment is not just good engineering practice—it is a mandatory safety requirement under the National Electrical Code (NEC/NFPA 70) . These provisions are designed to ensure safe operation, inspection, and maintenance of equipment rated at 600 Volts, nominal, or less . This article explains the key working space requirements , exceptions, and clearances mandated by NEC for low-voltage electrical systems. 1. General Requirement for Working Space Sufficient access and working space must be provided for safe operation, inspection, and maintenance . Spaces must comply with NEC specifications regarding depth, width, and height . No storage or obstruction is allowed in the designated working space. 2. Working Space Depth Requirements (a) Minimum Depth The minimum clear working distance depends on system volt...

NFPA 70 (NEC) – Examination, Identification, Installation, and Use of Electrical Equipment The National Electrical Code (NEC), NFPA 70 , establishes mandatory rules to ensure the safe installation and use of electrical equipment. Below is a simplified breakdown of key requirements: 1. Examination of Electrical Equipment Before approving equipment for installation, the following must be checked: Suitability for purpose/environment/application (labeling, instructions, or listing). Mechanical strength and durability of enclosures. Adequate space for wire bending and connections. Electrical insulation integrity. Heating and arcing effects under normal and abnormal conditions. Classification by type, voltage, and current rating. Other safety factors relevant to user protection. 2. Installation and Use Equipment must be installed as per listing or labeling instructions . Voltage rating of equipment ≥ circuit’s nominal voltage. Conductor materia...

Savings by Using LED Lights: Cost, Payback, and Long-Term Benefits LED lighting has become one of the most effective ways to reduce electricity bills at home and in industries. While the upfront cost of LED lights is slightly higher compared to conventional tube lights, the annual savings, longer lifespan, and reduced maintenance costs make them a far superior choice. Let’s break down the numbers and see why LEDs are a smart investment. Conventional Tube Light vs LED Tube Light – Power Consumption 1. Conventional Tube Light (with choke) Tube Wattage: 36 W Choke Wattage: 36 W Total Consumption per Hour: 72 W (0.072 kWh) Daily Usage (10 hours): 720 Wh (0.72 kWh) Monthly Usage (30 days): 21.6 kWh Annual Usage: 262.8 kWh Electricity Tariff (avg.): ₹8 per unit Annual Cost: ₹2,102 2. LED Tube Light Wattage: 20 W Total Consumption per Hour: 20 W (0.02 kWh) Daily Usage (10 hours): 200 Wh (0.20 kWh) Monthly Usage (30 days): 6 kWh Annu...

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...