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Sizing 2026-04-25 8 min readBy Ziyao Engineering Team

Transformer Sizing Guide

How to size transformers: load calculation, diversity factor, kVA rating selection, and future expansion margins.

Transformer Sizing Guide

Proper transformer sizing ensures reliable operation, energy efficiency, and adequate capacity for future growth.

Sizing Steps

  • Step 1: Calculate total connected load (kW)
  • Step 2: Apply diversity factor (0.7-0.9)
  • Step 3: Convert to kVA using power factor
  • Step 4: Add 20-25% future expansion margin
  • Step 5: Select next standard kVA rating

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