This question is specific to a MCC Incomer where ABB MCCB is being used rather than an ACB.
The MCCB short ckt interruption capcity is 70kA at 380V. But its short time withstand rating is only 7.3kA at 1 sec.
Now the prospective short circuit current at the MCC bus is 62kA.
If the Manin Incomer...
I have a simple question. Does any Code or Standard or any guideline ever specify that voltage drop of motors needs to take into consideration: a. Full load Amps (Nameplate rating) and b. Resistance of the conductor needs to be at the max temp of its insulation i.e 90degC? . The reason I ask...
I believe that NEC Article 450.3 Overcurrent Protection (and Table 450.3) directly determines the secondary side breaker sizing (and bus sizing).
For example, if I have a 2500kVA, 13.8-0.48kV Transformer, the rated secondary side current is 3007A. As per Table 450.3, for 480V secondary (<1000V)...
Once again posting this question for NEC based power distributiin design: Is it required for NEC based designs to use Equipment Grounding Conductor?
Article 250.36 High Impedance Grounded Neutral systems does not mention it (see A to G). Similarly, later in Part VII Methods of EGC Connection...
Has there been any publication for loop impedance calculations under NEC environment, identical to IEC or BS 7671? The table 250.122 in NEC provides the minimum EGC size for particular breaker. Is this size linked with loop impedance? Over and above voltage drop, do we need to establish loop...
Right now I don't have the Code book, but I believe that NEC requires the equipment grounding conductor for resistance grounded systems also. What is the rationale behind this? For eg. for a LV system with 10A resistor, we would only be detecting GF current using CBCTs and only for detection...
I have a 80kVA UPS (Chloride Apodys) with 120VAC, 1 phase, 60Hz output. Its a double redundant system with isolation transformers on the output side. The measured voltage at one of the consumer end is: L-N : 115VAC, N-G: 85V, L-G = 115VAC. This is a floating neutral system. The O&M Manual for...
IEC 60364-5-52 provides tables of cables ampacity derating factors (in single layer in trays). Highest number of cables is 9 with 6 layers of trays (spaced 300mm or more vertically). Now my query is: Has anybody worked out the derating factors for 2 layers/3 layers/random fill of cables in tray...
I am sure some of you have come across this problem. It seems that only few vendors offer ground fault detection/protection in their LV VFDs, for high resistance grounded system (5A). Please provide your feedback, and possible solutions. Thanks!!
As an electrical engineer, I have used numerous excel sheets for various purposes. The most common ones are:
a. Cable sizing-Ampacity
b. Cable sizing-Voltage drop & Short circuit
c. Heat Load Calculation
d. Load List
e. Lightning protection risk calculation
f. Cable Tray sizing
g. Cable Pull...
In one of our projects, we have a bunch of 480V VFDs in LV MCCs, which have not been used for the past 6 years. What are the steps required to ensure that these VFDs can be made operational? I understand that there are some issues regarding the DC capacitors. Please advise, if you have...
