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Transformer Sizing Calculator

AS 2374 / AS 60076 (Australian conditions)

✓ Phase 2 Calculator

Inputs

0.7–1.0 (default 0.8)

0.7–1.0 (default 0.85)

▶Advanced options

Results

Recommended Transformer Size

160

kVA

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Transformer Loading

% ()

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Standard Size Available

()

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Primary Voltage Valid

V ()

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Secondary Voltage Valid

V ()

Minimum Required kVA112.94
Recommended kVA160
Primary Current8.4 A
Secondary Current230.94 A
Loading70.59%
Important: These results are indicative only. Transformer sizing must be verified by a qualified electrical engineer against AS 2374 and manufacturer specifications before final design.

Transformer Sizing Guide — AS 2374 / AS 60076

Transformer sizing is a critical step in designing electrical installations. The transformer must be large enough to handle the connected load with a reasonable margin for future growth, but not so large that it operates inefficiently under normal conditions.

Key Sizing Factors

  • Total connected load (kW): The sum of all load power ratings at nameplate conditions.
  • Demand factor: Accounts for diversity and simultaneous use. Typical values: 0.7–0.9 for commercial, 0.8–1.0 for residential.
  • Power factor: Typically 0.85–0.95. Lower PF requires larger transformer (higher kVA).
  • Future growth: Plan for 10–20% headroom to avoid oversizing now or undersizing later.
  • Cooling type: ONAN (natural oil cooling) is standard; ONAF (forced cooling) reduces transformer size but adds cost.

Disclaimer: This calculator is provided as a guide only and must be verified by a qualified electrical engineer before use in design or installation. Always refer to the current edition of AS 2374 and AS 60076, and consult the transformer manufacturer for exact cooling and capacity ratings.