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Calculation of Size of Transformer, Fuse and Circuit Breaker
Calculation of Size of Transformer, Fuse and Circuit Breaker

Size of Circuit Breaker & Fuse are as per NEC 450.3

This MS Excel spreadsheet calculates the following:

  1. Size of Circuit Breaker on Primary side of Transformer as per NEC 450.3
  2. Size of Fuse on Primary side of Transformer as per NEC 450.3
  3. Size of Circuit Breaker on Secondary side of Transformer as per NEC 450.3
  4. Size of Fuse on Secondary side of Transformer as per NEC 450.3
  5. Size of Transformer
  6. Transformer Full Load Losses.

Overcurrent Protection of Transformer (NEC 450.3)

This technical article was written by author Jignesh Parmar explains step by step NEC 450.3 (Transformer protection).

Software:Calculation of Size of Transformer, Fuse and Circuit Breaker
Version:10.6.13
Developer:Jignesh Parmar
Size:90.3 KB
Price:Free
Download:Right here | Video Courses | Membership | Download Updates
Calculation of Size of Transformer, Fuse and Circuit Breaker
Calculation of Size of Transformer, Fuse and Circuit Breaker

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22 Comments


  1. Bob pham
    Apr 18, 2023

    Great tool


  2. Priyanand
    Apr 04, 2023

    How to size the circuit breaker based on the inrush current? Can a formula be included in the excel file to calculate the inrush current, and pick a required CB based on the Long/Medium delay, due to inrush current?

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