Transformers

Practical transformer guides for engineers, estimators, and installers: how to size the kVA rating, apply demand and diversity factors, and select protection and conductors that meet code. Start with the guides below, or browse every article underneath.

Transformer Sizing Guides

• Distribution Transformer Sizing: Load Calculation and kVA Selection
• Dry Type Transformer Sizing Chart
• Transformer Sizing for Residential Buildings
• Auxiliary Transformer Sizing Calculation
• Buck and Boost Transformer Sizing

Load Factors

• Demand Factor for Transformer Sizing
• Diversity Factor for Transformer Sizing

Protection, Neutral and Grounding

• Transformer OCPD Sizing Chart (Breaker and Fuse, NEC)
• Transformer Neutral Sizing
• Transformer Ground Size Chart

Solar Plant Transformers

• Transformer Sizing for Solar Power Plants
• Best Medium Voltage Transformers for Solar Plants

Transformer Suppliers (UAE)

• Top 15 Transformer Manufacturing Companies in UAE
• Top 7 Transformer Assembly Suppliers in UAE

Transformer Sizing Basics

kVA formulas: Single-phase kVA = V × I ÷ 1000. Three-phase kVA = √3 × V × I ÷ 1000. Calculate the connected load first, then apply demand and diversity factors to avoid oversizing.

Spare capacity: Designers commonly add a margin for future growth, then round up to the next standard kVA rating. Confirm the margin against your project specification.

Protection: In the US, transformer overcurrent protection is covered by NEC Article 450. Primary and secondary protection are sized differently, so use the OCPD chart for the exact rules.

Grounding: Grounding conductor size depends on the supply conductors and the overcurrent device rating. Always verify against the code edition adopted in your jurisdiction.

All Transformer Articles